TY - GEN A1 - Hoffmann, Patrick A1 - Mikalo, Ricardo Pablo A1 - Yfantis, Alexandros D. A1 - Batchelor, David R. A1 - Appel, Günter A1 - Schmeißer, Dieter T1 - A Spectro-Microscopic Approach for Thin Film Analysis Grain Boundaries in mc-Si and Sn/SnO2 Nano Particles T2 - Microchimica Acta Y1 - 2001 SN - 1436-5073 SN - 0026-3672 VL - 136 IS - 3-4 SP - 109 EP - 113 ER - TY - GEN A1 - Müller, Klaus A1 - Paloumpa, Ioanna A1 - Henkel, Karsten A1 - Schmeißer, Dieter T1 - A polymer high-k dielectric insulator for organic field effect Transistors T2 - Journal of Applied Physics Y1 - 2005 SN - 0021-8979 VL - 98 IS - 5 SP - S. 056104 ER - TY - JOUR A1 - Schmitt, Andrew L. A1 - Zhu, Lei A1 - Schmeißer, Dieter A1 - Himpsel, Franz J. A1 - Jin, Song T1 - Metallic Single-Crystal CoSi Nanowires via Chemical Vapor Deposition of Single-Source Precursor Y1 - 2006 ER - TY - JOUR A1 - Schmitt, Andrew L. A1 - Bierman, Matthew J. A1 - Schmeißer, Dieter A1 - Himpsel, Franz J. A1 - Jin, Song T1 - Synthesis and Properties of Single-Crystal FeSi Nanowires Y1 - 2006 ER - TY - GEN A1 - Schmeißer, Dieter A1 - Henkel, Karsten A1 - Müller, Klaus A1 - Tallarida, Massimo T1 - Interface Reactions in Ultrathin Functional Dielectric Films KW - ultrathin KW - dielectric Y1 - 2009 ER - TY - GEN A1 - Lazareva, I. A1 - Koval, Yuri A1 - Müller, P. A1 - Müller, Klaus A1 - Henkel, Karsten A1 - Schmeißer, Dieter T1 - Interface screening and imprint in pol(vinylidene fluoride/trifluoroethylene) ferroelectric field effect transistors KW - interface KW - screening KW - transistors Y1 - 2009 ER - TY - CHAP A1 - Müller, Klaus A1 - Burkov, Yevgen A1 - Mandal, Dipankar A1 - Henkel, Karsten A1 - Paloumpa, Ioanna A1 - Goryachko, Andriy A1 - Schmeißer, Dieter ED - Wöll, Christof T1 - Microscopic and spectroscopic characterization of interfaces and dielectric layers for OFET devices T2 - Organic Electronics : structural and Electronic Properties of OFETs KW - microscopic KW - spectrocsopic KW - dielectric Y1 - 2009 SN - 978-3-527-40810-8 SP - 445 EP - 468 PB - Wiley-VCH CY - Weinheim ER - TY - GEN A1 - Tallarida, Massimo A1 - Karavaev, Konstantin A1 - Schmeißer, Dieter T1 - HfO2/Si interface formation in atomic layer deposition films: an in situ investigation KW - atomic layer deposition Y1 - 2009 ER - TY - JOUR A1 - Hoffmann, Patrick A1 - Mikalo, Ricardo Pablo A1 - Schmeißer, Dieter T1 - Si(001) surface oxidation by N2O N2 - Ultra-thin homogeneous oxynitride films are prepared on Si(001). The Si surface is cleaned in UHV by heating (flashing) and is exposed to different pressures of N2Oat altered temperatures. Thus oxynitride layers of different thickness and different properties are grown depending on the N2O pressure and the Si temperature. This isillustrated by a schematic diagram. The properties of the different oxynitride layers were studied by a combined photoemission electron microscopy (PEEM) andphotoelectron spectroscopy (PES) investigation using highly monochromatic synchrotron radiation. The amount of oxygen and nitrogen incorporated in the oxynitridelayers is determined from the PES measurements. The typical surface morphology for different preparation conditions is shown in PEEM images. KW - SI(100) KW - dielectric KW - Oxynitride KW - Interface KW - SI KW - NO Y1 - 2002 ER - TY - JOUR A1 - Schmeißer, Dieter A1 - Hoffmann, Patrick T1 - Characterisation of the PrOx/Si(001) Interface by Photoelectron Spectroscopy Y1 - 2002 ER - TY - GEN A1 - Henkel, Karsten A1 - Sohal, Rakesh A1 - Torche, Mohamed A1 - Paloumpa, Ioanna A1 - Müller, Klaus A1 - Hoffmann, Patrick A1 - Schmeißer, Dieter T1 - Grenzflächenoptimierung für funktionale Dünnschichtsysteme: Oxide und Polymere T2 - Forum der Forschung Y1 - 2005 SN - 0947-6989 VL - 9 IS - 18 SP - 49 EP - 56 ER - TY - GEN A1 - Schmeißer, Dieter A1 - Himpsel, Franz J. A1 - Denlinger, Jonathan D. A1 - Ederer, David L. T1 - Resonante Photoemission an der Cu2p Kante von Cu und CuO T2 - Forum der Forschung Y1 - 2005 SN - 0947-6989 VL - 9 IS - 18 SP - 57 EP - 62 ER - TY - JOUR A1 - Müller, Klaus A1 - Burkov, Yevgen A1 - Schmeißer, Dieter T1 - Photo-Emission-Electron-Microscopy for Characterization of an Operating Organic Electronic Device KW - photo-emission-electron-microscopy Y1 - 2006 ER - TY - JOUR A1 - Schmeißer, Dieter T1 - The Consequences of anisotropic Diffusion and Noise: PEEM at the CO Oxidation Reaction on Stepped Ir(111) Surfaces KW - Ir(111) Surfaces Y1 - 2006 ER - TY - GEN A1 - Müller, Klaus A1 - Henkel, Karsten A1 - Mandal, Dipankar A1 - Seime, Bernd A1 - Paloumpa, Ioanna A1 - Schmeißer, Dieter T1 - Spin coated organic ferroelectric films for non volatile memories KW - organic KW - ferroelectric Y1 - 2011 ER - TY - GEN A1 - Seifarth, Olaf A1 - Schubert, Markus Andreas A1 - Giussani, A. A1 - Klenov, D. O. A1 - Schmeißer, Dieter A1 - Schroeder, Thomas T1 - Single crystalline Pr2-xYxO3 (x=0-2)dielectrics on Si with tailored electronic and crystallographic structure KW - crystalline KW - dielectric KW - structure Y1 - 2010 SN - 1089-7550 VL - 108 IS - 10 SP - 103709 ER - TY - GEN A1 - Mandal, Dipankar A1 - Henkel, Karsten A1 - Müller, Klaus A1 - Schmeißer, Dieter T1 - Band gab determination of P(VDF-TrFE) copolymer film by electron energy loss spectroscopy Y1 - 2010 ER - TY - GEN A1 - Kolanek, Krzysztof A1 - Tallarida, Massimo A1 - Karavaev, Konstantin A1 - Schmeißer, Dieter T1 - In situ studies of the atomic layer deposition of thin HfO2 dielectrics by ultra high vacuum atomic force microscope KW - in situ KW - atomic layer deposition KW - dielectric KW - microscope Y1 - 2010 ER - TY - JOUR A1 - Schmeißer, Dieter A1 - Seibold, Götz A1 - Reif, Jürgen T1 - Nano-scaled Dielectric Barriers (NanoDieB) for CMOS compatible Si-technologies JF - Forum der Forschung KW - nano-scaled KW - dielectric KW - CMOS Y1 - 2006 SN - 0947-6989 IS - 19 SP - 131 EP - 136 ER - TY - CHAP A1 - Starzyk, Łukasz A1 - Tallarida, Massimo A1 - Schmeißer, Dieter T1 - Band alignment of high-k/SiO2/Si stacks incorporating Zr and Al oxides prepared by atomic layer deposition Y1 - 2010 ER - TY - GEN A1 - Kolanek, Krzysztof A1 - Tallarida, Massimo A1 - Schmeißer, Dieter T1 - Atomic layer deposition of HfO2 investigated in situ by means of a noncontact atomic force microscopy Y1 - 2010 ER - TY - CHAP A1 - Gehrlich, Lukas A1 - Ohsiek, Susanne A1 - Klein, M. A1 - Geiss, M. A1 - Friedemann, Michael A1 - Kücher, Peter A1 - Schmeißer, Dieter T1 - Ultrathin TaN/Ta barrier modifications to fullfill next technology node requirements T2 - 2011 IEEE International Interconnect Technology Conference and 2011 Materials for Advanced Metallization (IITC/MAM 2011), Dresden, Germany, 8 - 12 May 2011 Y1 - 2011 SN - 978-1-4577-0503-8 U6 - https://doi.org/10.1109/IITC.2011.5940322 SP - 82 EP - 84 PB - IEEE CY - Piscataway, NJ ER - TY - CHAP A1 - Richter, Matthias A1 - Friedrich, Daniel A1 - Philip, Shine A1 - Paloumpa, Ioanna A1 - Müller, Klaus A1 - Schmeißer, Dieter T1 - Study of P3HT/PCBM based films by NEXAFS T2 - Verhandlungen der Deutschen Physikalischen Gesellschaft, Reihe 6, Bd. 45 N2 - In this contribution we report on investigations of the electronic structure and composition of regioregular poly(3-hexylthiophene) (P3HT) and phenyl-C61-butyric acid methyl ester (PCBM) based films by using Near Edge X-Ray Absorption Fine Structure (NEXAFS). The measurements were done at the U49/2-PGM2 beam line of BESSY II, Berlin using TEY (total electron yield) and TFY (total fluorescence yield) detection. The samples were produced by spin casting a mixture of P3HT (dissolved in chloroform) and PCBM (dissolved in chlorobenzene) on ITO (indium tin oxide) coated glass slides. Measurements of pure P3HT and PCBM show all typical excitations, whereas the blended system is a weighted superposition of the related peaks. Analyzing these weighted superposition, we observe in the surface sensitive TEY data an accumulation of P3HT, whereas in the bulk sensitive TFY signal an as expected mixture is found. We also show angular dependent NEXAFS measurements of the P3HT/PCBM blend in order to measure the orientation and distribution of the P3HT polymer. Additionally, we will show a new approach for organic solar cell application by introducing ferroelectric nanoparticles into the mixture. Y1 - 2010 UR - http://www.dpg-verhandlungen.de/year/2010/conference/regensburg/part/df/session/7/contribution/4 SN - 0420-0195 SP - S. 194 PB - Deutsche Physikalische Gesellschaft CY - Bad Honnef ER - TY - CHAP A1 - Schmidt, Stephan A1 - Schmeißer, Dieter T1 - Cobalt/nickel mixed oxides - cathode materials for Li-Ion-Batteries T2 - Verhandlungen der Deutschen Physikalischen Gesellschaft, Reihe 6, Bd. 45 N2 - Replacing Co by large amounts of Ni is considered to reduce costs in Li-Ion-Batteries while maintaining their performance. We are interested in whether this replacement causes changes in the valence band (VB) and conduction band (CB) states or not. Samples were prepared as thin films from nitrate solutions on metal substrates and annealed in air and UHV. The Co to Ni ratio was varied from 50/50 over 40/60 and 30/70 up to 20/80. The results are compared to the pure Co-oxide. Experiments were carried out at the U49/2 beamline at BESSYII, Berlin. XPS of the TM2p states reveals the existence of charge transfer ground states and different oxidation states. NEXAS at the Co2p, Ni2p and O1s edges projects the density of unoccupied states while resonant PES at these edges provides the related partial density of states (pDOS) and thus can be used to distinguish between the different contributions of TM3d and O2p states in the valence band region. We find systematic variation of the VB structure, the valence band maximum and a shift at the O1s absorption edge while the TM2p XPS and absorption spectra do not seem to be affected by the mixing. Y1 - 2010 UR - http://www.dpg-verhandlungen.de/year/2010/conference/regensburg/part/o/session/45/contribution/6 SN - 0420-0195 SP - S. 596 PB - Deutsche Physikalische Gesellschaft CY - Bad Honnef ER - TY - CHAP A1 - Müller, P. A1 - Chowdhury, F. A1 - Dremov, V. A1 - Koval, Yuri A1 - Lichtenberg, F. A1 - Müller, S. A1 - Schmeißer, Dieter A1 - Pentcheva, R. T1 - Resistive memory switching in perovskite-derivative single crystals T2 - Verhandlungen der Deutschen Physikalischen Gesellschaft, Reihe 6, Bd. 43 N2 - We investigated several layered perovskite derivatives of the family AnBnO3n+2, such as LaTiO3.41, CaNbO3.41 and SrNbO3.41, which can be considered as a stacking of blocks consisting of 5 perovskite layers. Electric transport across these layers takes place via intrinsic tunnelling. Mesa devices with a cross-sectional area of 50 to 200 µm2 and a height between 30 and 500 nm were fabricated by electron-beam lithography and ion-beam etching. Both dc I-V characteristics and pulsed current injection have shown switching between different resistive states in these materials. The resistive states have long-term stability, which makes them interesting for memory applications. The transport experiments suggest that switching and resistive memory are controlled by trapping and release of charge carriers. Furthermore, photoelectron and NEXAFS spectroscopy of cleaved LaTiO3.41 surfaces have been performed. The results are compared to recent correlated band theory (LDA+U) calculations. Y1 - 2008 UR - http://www.dpg-verhandlungen.de/year/2008/conference/berlin/part/synf/session/1/contribution/11 SN - 0420-0195 SP - S. 818 PB - Deutsche Physikalische Gesellschaft CY - Bad Honnef ER - TY - GEN A1 - Müller, K. A1 - Goryachko, Andriy A1 - Burkov, Yevgen A1 - Schwiertz, Carola A1 - Ratzke, Markus A1 - Köble, J. A1 - Reif, Jürgen A1 - Schmeißer, Dieter T1 - Scanning Kelvin probe and photoemission electron microscopy of organic source-drain structures T2 - Synthetic Metals Y1 - 2004 VL - 146 IS - 3 SP - 377 EP - 382 ER - TY - GEN A1 - Das, Chittaranjan A1 - Richter, Matthias A1 - Tallarida, Massimo A1 - Schmeißer, Dieter T1 - Electronic properties of atomic layer deposited films, anatase and rutile TiO2 studied by resonant photoemission spectroscopy T2 - Journal of Physics D: Applied Physics N2 - The TiO2 films are prepared by atomic layer deposition (ALD) method using titanium isopropoxide precursors at 250 °C and analyzed using resonant photoemission spectroscopy (resPES). We report on the Ti2p and O1s core levels, on the valence band (VB) spectra and x-ray absorption spectroscopy (XAS) data, and on the resonant photoelectron spectroscopy (resPES) profiles at the O1s and the Ti3p absorption edges. We determine the elemental abundance, the position of the VB maxima, the partial density of states (PDOS) in the VB and in the conduction band (CB) and collect these data in a band scheme. In addition, we analyze the band-gap states as well as the intrinsic states due to polarons and charge-transfer excitations. These states are found to cause multiple Auger decay processes upon resonant excitation. We identify several of these processes and determine their relative contribution to the Auger signal quantitatively. As our resPES data allow a quantitative analysis of these defect states, we determine the relative abundance of the PDOS in the VB and in CB and also the charge neutrality level. The anatase and rutile polymorphs of TiO2 are analyzed in the same way as the TiO2 ALD layer. The electronic properties of the TiO2ALD layer are compared with the anatase and rutile polymorphs of TiO2. In our comparative study, we find that ALD has its own characteristic electronic structure that is distinct from that of anatase and rutile. However, many details of the electronic structure are comparable and we benefit from our spectroscopic data and our careful analysis to find these differences. These can be attributed to a stronger hybridization of the O2p and Ti3d4s states for the ALD films when compared to the anatase and rutile polymorphs. KW - titanium dioxide (TiO2) KW - resonant photoemission spectroscopy (resPES) KW - defect states KW - partial density of states (pDOS) KW - charge neutrality level (CNL) Y1 - 2016 U6 - https://doi.org/10.1088/0022-3727/49/27/275304 SN - 0022-3727 SN - 1361-6463 VL - 49 IS - 27 SP - 275304-1 EP - 275304-17 ER - TY - CHAP A1 - Müller, Klaus A1 - Milko, Sergey A1 - Burkov, Yevgen A1 - Schmeißer, Dieter T1 - Mischkristalle des Systems ZnS-CuInS2 für multispektrale Solarzellen T2 - Verhandlungen der Deutschen Physikalischen Gesellschaft N2 - Wir haben CuInS2 (CIS) unterschiedlicher Herstellung (Koverdampfung, Sputtern, Pulsed Laser Deposition, CIS auf Kupferband aufgebracht) untersucht. Neben Tiefenprofilen (durch Sputtern) der Elementverteilung dieser Proben wurden der Einfluss der Temperatur, von aufgedampftem Kupfer und Indium, ebenfalls bei verschiedenen Temperaturen, auf das Verhalten der Stöchiometrie mit spektroskopischen Methoden (XPS, UPS) studiert. Parallel dazu wurde das Verhalten von im Vakuum aufgedampften ZnS und die entsprechenden Oberflächenreaktionen in Abhängigkeit von der Temperatur untersucht und charakterisiert, so dass Aussagen über die Optimierung und Anpassung von Präparationsbedingungen und Parametern zur Herstellung von erstens reinem CIS und zweitens von Mischkristallen des Typs Zn2-xCuxInxS2 möglich werden. Zwischen den beiden Endgliedern ZnS und CuInS2 besteht bis auf einen Phasenübergang bei etwa 80% CIS lückenlose Mischbarkeit gemäss Zn2-xCuxInxS2 (Bente: Chem.Erde (1991)). Die elektronische Bandlücke dieser Mischkristalle lässt sich im Vergleich zu reinem CuInS2 in einem Bereich von 3,67 eV (ZnS) bis 1,55 eV (CuInS2) variieren. Damit besteht die Möglichkeit, durch kontrollierte Änderung der Zusammensetzung der Schichten die Effizienz von Solarzellen aus diesem Material zu optimieren. KW - CIS-Solarzellen KW - Röntgen-Photoelektronenspektroskopie KW - Tiefenprofilierung Y1 - 2002 PB - Deutsche Physikalische Gesellschaft CY - Bad Honnef ER - TY - CHAP A1 - Heller, Thomas A1 - Lopez, Alberto A1 - Bitzer, Thomas A1 - Richardson, Neville V. A1 - Schmeißer, Dieter T1 - The Adsorption of Maleic Anhydride on Si(100)-2x1: A Combined HREELS and NEXAFS Study T2 - Verhandlungen der Deutschen Physikalischen Gesellschaft N2 - Due to the growing range of applications for organic materials considerable interest has been focused on the controlled growth of films on silicon substrates. Recently, it has been shown that ultra-thin oligimide films can be grown on Si(100)-2x1 with a direct Si-C linkage to the substrate. In this study, we have focused on the chemisorption of maleic anhydride (C4O3H2) on Si(100)-2x1. The combined HREELS data indicate that the adsorption of maleic anhydride on Si(100)-2x1 at low dosages occurs mainly through cycloaddition of the C=C bond to the dangling bonds of the Si-Si dimer analogous to the behaviour of ethene. The Si-Si dimer bonds are not involved in the chemisorption, as the continued observation of a 2x1 pattern in LEED shows. In the NEXAFS spectra, a π* resonance indicative of a C=C bond is absent upon exposure of the silicon substrate to maleic anhydride. At higher dosages, we observe chemisorbed maleic anhydride species, which are bonded to the Si surface atoms via a single Si-C linkage with preservation of the C=C double bond. In this case, the dissociated hydrogen bonds to one of the neighbouring Si atoms. Possible adsorption geometries will be discussed. KW - adsorption KW - maleic anhydride KW - High resolution electron energy loss spectroscopy (HREELS) KW - low-energy electron diffraction (LEED) KW - Near-edge X-Ray absorption spectroscopy (NEXAFS) Y1 - 2000 UR - http://www.dpg-verhandlungen.de/year/2000/conference/regensburg/part/o/session/11/contribution/56?lang=en PB - Deutsche Physikalische Gesellschaft CY - Bad Honnef ER - TY - CHAP A1 - Hoffmann, Patrick A1 - Mikalo, Ricardo Pablo A1 - Schmeißer, Dieter A1 - Kittler, Martin T1 - Spektro-Mikroskopie auf multikristallinem Silizium T2 - Verhandlungen der Deutschen Physikalischen Gesellschaft N2 - Es werden spektro-mikroskopische Untersuchungen an multikristallinem Silizium (mc-Si) vorgestellt, einem aussichtsreichen Material für die Herstellung preiswerter Solarzellen. Dazu wird ein Photoemissions- Elektronenmikroskop (PEEM) ausgestattet mit einem zusätzlichen Energieanalysator für Elektronen (µESCA) genutzt. Bei Verwendung eines Synchrotrons als Anregungsquelle ist es so möglich, sowohl Absorbtions-Spektren (NEXAFS) als auch Photoelektronen-Spektren (PES) mit Ortsauflösung zu erhalten. Dabei wird gezeigt, dass das natürliche Oxid zur Untersuchung der morphologie-abhängigen Oberflächenpotentiale nicht entfernt werden muss. Des Weiteren wird die Verteilung von Ca- und Na-Ausscheidungen, die auf dem mc-Si gefunden wurden, durch ortsaufgelöstes NEXAFS bzw. PES dargestellt. Für den Photoemissions-Prozess des mc-Si im PEEM wird ein Modell aufgestellt, welches Photoemission mit einer Quecksilberdampflampe (hνmax = 4,9 eV) erklärt. KW - mc-Si KW - Solarzellen KW - Röntgen-Photoelektronenspektroskopie (XPS) KW - Röntgen-Absorptionsspektroskopie (XAS, NEXAFS) KW - Photoemissionselektronenspektroskopie (PEEM) Y1 - 2000 UR - http://www.dpg-verhandlungen.de/year/2000/conference/regensburg/part/hl/session/16/contribution/10?lang=en PB - Deutsche Physikalische Gesellschaft CY - Bad Honnef ER - TY - CHAP A1 - Mikalo, Ricardo Pablo A1 - Appel, Günter A1 - Hoffmann, Patrick A1 - Schmeißer, Dieter T1 - Conducting Polypyrrole doped with Phthalocyaninesulfonates - new materials for chemical sensors T2 - Verhandlungen der Deutschen Physikalischen Gesellschaft N2 - Polypyrrole - a conducting polymer - is used as an active electrode of a quartz micro ballance and considered as a gate electrode in all-polymer field effect transistors used as chemical sensor. We use substituted phthalocyanines as dopants of polypyrrole as they offer the possibility to enhance the dopant concentration as well as to include functionalized groups. We studied these films by photoelectron spectroscopy, NEXAFS, PEEM, and TEM. These investigations revealed that the electronic structure as well as the morphology are highly dependent on the dopant’s structure. We suggest a new charge transport model for 5-ring heterocycle conductive polymers. Whereas in the standard model only the carbon backbone is considered for the charge transport, we found by NEXAFS investigations that the heteroatom has a considerable high participation in the gap states, which are responsible for the charge transport. The dopants π-interactions force the nitrogen lone pair wave functions to contribute to the conducting polymer π-system. This is a novel approach concerning the application as chemical sensors since the reversible interaction of the analyte modifies the dopant and not the matrix. KW - polypyrrole KW - conducting polymer KW - X-ray photoelectron spectroscopy (XPS) KW - X-Ray absorption spectroscopy (XAS) KW - photo emission electron spectroscopy (PEEM) KW - transmission electron microscopy (TEM) KW - quartz crystal micro ballance (QMB) KW - gas sensor Y1 - 2000 UR - http://www.dpg-verhandlungen.de/year/2000/conference/regensburg/part/o/session/15/contribution/1?lang=en PB - Deutsche Physikalische Gesellschaft CY - Bad Honnef ER - TY - CHAP A1 - Hoffmann, Patrick A1 - Böhme, Oliver A1 - Schmeißer, Dieter A1 - Lloyd Spetz, Anita A1 - Mårtenson, Per T1 - Einfluß von Nanopartikeln auf die Funktion von Hochtemperatursensoren T2 - Verhandlungen der Deutschen Physikalischen Gesellschaft N2 - Es werden Untersuchungen an als Hochtemperatur-Sensoren arbeitenden Schottky-Dioden mit dem Aufbau Metall-Oxidschicht-Siliziumkarbid vorgestellt. Dazu wurden Tiefenprofile mit XPS durch abwechselndes Abtragen durch Sputtern und Messen erstellt. Die Messungen erfolgten an thermisch unterschiedlich vorbehandelten Proben. Dabei konnten dipol-bedingte Verschiebungen der Bindungsenergie von Rumpfniveaus beobachtet werden. Das dazu notwendige Dipol-Moment wird durch das Entstehen von mit einer Oxidschicht überzogenen Nanoteilchen erklärt. Die unterschiedlich ausgeprägten Dipol-Verschiebungen auf den einzelnen Proben erlaubten eine Erklärung der thermischen Vorbehandlung, die bei Weglassen zu „frischen“ und je nach Temperatur zu „aktivierten“ oder „toten“ Sensoren führte. KW - Hochtemperatursensoren KW - Röntgen-Photoelektronenspektroskopie (XPS) KW - Tiefenprofilierung Y1 - 1999 UR - http://www.dpg-verhandlungen.de/year/1999/conference/muenster/part/o/session/16/contribution/1?lang=en PB - Deutsche Physikalische Gesellschaft CY - Bad Honnef ER - TY - CHAP A1 - Mikalo, Ricardo Pablo A1 - Appel, Günter A1 - Hoffmann, Patrick A1 - Schmeißer, Dieter T1 - Leitfähiges Polypyrrol als Elektrodenmaterial: Wechselwirkungen mit Silber T2 - Verhandlungen der Deutschen Physikalischen Gesellschaft N2 - Untersuchungen des metallischen Kontaktes von Silber auf tosylat- und phthalocyanindotiertem Polypyrrol wurden mittels XPS- und µ-NEXAFS vorgenommen. Es wurde festgestellt, daß Silber mit dem Polypyrrol keine Verbindung eingeht. Daraus kann geschlossen werden, daß sowohl das leitfähige Polymer, als auch das Silber ihren Leitfähigkeitsmechanismus beibehalten. Es konnte gezeigt werden, daß bei steigender Silberbelegung die Intensität der Polaronenzustände des Polypyrrol in stärkerem Maße abnimmt, als die Intensität der unbesetzten Zustände. Das läßt darauf schließen, daß Silber die Grenzfläche stabilisiert. KW - Polypyrrol KW - leifähiges Polymer KW - Röntgen-Photoelektronenspektroskopie (XPS) KW - Röntgen-Absoprtionsspektroskopie (XAS, NEXAFS) Y1 - 1999 UR - http://www.dpg-verhandlungen.de/year/1999/conference/muenster/part/o/session/11/contribution/57?lang=en PB - Deutsche Physikalische Gesellschaft CY - Bad Honnef ER - TY - CHAP A1 - Heller, Thomas A1 - Böhme, Oliver A1 - Schmeißer, Dieter T1 - Gap - Zustände in Wolframoxid WO3 - relaxierten Oberflächen T2 - Verhandlungen der Deutschen Physikalischen Gesellschaft N2 - Vorgestellt werden Arbeiten an dünnen WO3-Schichten, die durch Verdampfen aus einer Knudsenzelle im UHV präpariert wurden. Diese Filme sind im Rahmen der XPS-Analysen stöchiometrisch, ohne Gap-Zustände. Definierte Gap-Zustände bilden sich durch Relaxierung der Oberfläche: nach einigen Stunden im UHV, nach Heizen in Argon-Atmosphäre und nach Belegung mit Natrium. Die Charakterisierung dieser definierten Wolframoxid-Schichten erfolgt durch: 1.)XPS-Intensitäten 2.)detailierte Analyse der W4f-Rumpfniveaus durch Synchrotronstrahlung (Bessy, TGM 7) 3.)die Variation der Austrittsarbeit beim Heizen und bei Natrium-Belegung 4.)das Auftreten von Gap-Zuständen in der Bandlücke KW - WO3 KW - Röntgen-Photoelektronenspektroskopie (XPS) KW - Gapzustände Y1 - 1998 UR - http://www.dpg-verhandlungen.de/year/1998/conference/regensburg/part/o/session/11/contribution/102?lang=en PB - Deutsche Physikalische Gesellschaft CY - Bad Honnef ER - TY - CHAP A1 - Hoffmann, Patrick A1 - Mikalo, Ricardo Pablo A1 - Schmeißer, Dieter T1 - PEEM-Untersuchung an Spaltflächen von MoTe2-(0001) T2 - Verhandlungen der Deutschen Physikalischen Gesellschaft N2 - Molybdänditellurid (MoTe2) gehört zu den Schichtgitterverbindung und ist im allgemeinen durch den Herstellungsprozeß n-dotiert. Proben dieses MoTe2 wurden im Ultrahochvakuum gespalten und die so erhaltenen sauberen (0001)-Spaltflächen mit einem Photoemissions-Elektronenmikroskop (PEEM) untersucht. Diese Untersuchung erbrachte nebeneinander auf den Proben- oberflächen liegende stark kontrastierte helle und dunkle Bereiche. Da das PEEM Austrittsarbeitsunterschiede als Kontrast darstellt, können diese hellen und dunklen Bereiche auf lokale Unterschiede in der Austrittsarbeit zurückgeführt werden. Weiterhin wird über den Versuch berichtet, eine Zuordnung zwischen dem Kontrast und dem Unterschied in der Austrittsarbeit mit Hilfe eines Elektronenenergie-Analysators (micro-ESCA) zu treffen. KW - MoTe2 KW - Photoemissionselektronenspektroskopie (PEEM) KW - Austrittsarbeit Y1 - 1998 UR - http://www.dpg-verhandlungen.de/year/1998/conference/regensburg/part/o/session/5/contribution/5?lang=en PB - Deutsche Physikalische Gesellschaft CY - Bad Honnef ER - TY - CHAP A1 - Łobaza, Justyna A1 - Kot, Małgorzata A1 - Schmeißer, Dieter T1 - Analysis of surface oxidation of TiON ALD films T2 - Verhandlungen der Deutschen Physikalischen Gesellschaft N2 - Titanium oxynitride (TiON) films are interesting due to their remarkable optical and electronic properties which strongly depend on the O/N ratio. However, it is known that films containing Ti are prone to oxidation in contact with the air [1]. In this work, we study the thickness of a surface oxidation layer which is inherently formed on the atomic layer deposition (ALD) grown TiON/TiN films on Si substrate. We use an Ar+ ion bombardment source and X-ray photoelectron spectroscopy (XPS) for this analysis. We calibrate the sputter rate by using substrate signal intensity decay (here Si 2p) in the XPS spectra of the 5 nm thick TiON sample accordingly. This rate is assumed to be constant when films with a larger thickness are analyzed. We find that the surface oxidation layer is about 1 nm thick, independent on the detailed ALD parameters of the films. The TiN films found underneath are close to the stoichiometric values and have a residual O content below 5%. Finally, we compare these data to our previous results collected with synchrotron-based radiation source [2,3]. References: [1] Sowinska et al., Applied Physics Letters 100, 233509 (2012). [2] M. Sowinska et al., Applied Surface Science 381, 42-47 (2016). [3] M. Sowińska et al., Journal of Vacuum Science and Tech- nology A, 01A12734 (2016). KW - titanium oxynitride KW - X-Rax photoelectron spectroscopy KW - depth profiling KW - sputtering Y1 - 2017 UR - http://www.dpg-verhandlungen.de/year/2017/conference/dresden/part/ds/session/21/contribution/7 SN - 0420-0195 SP - S. 202 PB - Deutsche Physikalische Gesellschaft CY - Bad Honnef ER - TY - GEN A1 - Schmeißer, Dieter A1 - Janowitz, Christoph T1 - Two polarization dependent Auger decays observed by resonant photoelectron spectroscopy at the Cu2p-edge of superconducting BiSrCu-oxides T2 - Nuclear Instruments and Methods in Physics Research B N2 - We report on a resonant photoemission (resPES) study of PbxBi2-xSr2-yLayCan-1CunO2n+4+d (BISCO) single crystals to unravel the resonant decay mechanisms at the Cu2p absorption edge. The resPES studies on superconducting BISCO are performed at Bessy U49/2. We investigated BISCO single crystals with different hole doping concentrations at temperatures between 300 K and 17 K. CuO films have been used as a reference. We focus on the resPES data recorded at the Cu2p absorption edge. We find a strong polarization dependence for in-plane and out-of-plane geometries (with respect to the Cu-O plane) in our data which are caused by two independent Auger processes. We also report on the influence of different doping concentrations. Our resPES data enable us to sort the individual resonant mechanisms at the Cu2p edge in more detail than recently anticipated (Brookes et al., 2015). We discuss our data in the context of the recent discussion about the applicability of the Zhang-Rice model (Chen et al., 2013). KW - Synchrotron radiation KW - Superconductor KW - Cuprates KW - Resonant photoemission Y1 - 2017 U6 - https://doi.org/10.1016/j.nimb.2017.01.084 SN - 0168-583X SN - 1872-9584 VL - 411 SP - 53 EP - 56 ER - TY - CHAP A1 - Garain, Samiran A1 - Henkel, Karsten A1 - Mandal, Dipankar A1 - Schmeißer, Dieter T1 - One-Pot Synthesis of Copper Oxide Nanowires and PVDF/CuO Composite Films for Piezoelectric Energy Harvesting Application T2 - Verhandlungen der Deutschen Physikalischen Gesellschaft, Reihe 6, Band 53,3 N2 - Copper oxide (CuO) is an attractive p-type oxide semiconductor with narrow band gap that has intriguing properties such as non-toxicity, chemical stability, electrocatalytic activity, abundant availability and low production cost. Polymeric materials have attracted great interest owing to their high flexibility, light weight, low cost production and high resistance against corrosion. Poly(vinylidene fluoride) (PVDF) is a commonly used piezoelectric polymer due to its excellent flexibility and piezoelectric properties. In this work, we adopted a one-pot synthesis of CuO nanowires by facile and selective chemical etching process of Cu substrate. XPS, XRD, SEM data ascribed the formation of polycrystalline CuO nanowires over the entire Cu surface. It has been observed that the uniformity, shape and size of the nanowires could be conveniently controlled by etching time and etchant concentration. We have also prepared piezoelectric nanogenerator based on the flexible PVDF/CuO composite film, where the traditional electrical poling treatment was avoided. In addition, dielectric properties have been studied to demonstrate the role of interfacial polarization. KW - PVDF KW - electroactive phase KW - nanogenerators KW - energy storage Y1 - 2018 UR - https://www.dpg-verhandlungen.de/year/2018/conference/berlin/part/cpp/session/20/contribution/21 SN - 0420-0195 SP - S. 135 PB - Deutsche Physikalische Gesellschaft CY - Bad Honnef ER - TY - CHAP A1 - Kot, Małgorzata A1 - Naumann, Franziska A1 - Garain, Samiran A1 - Poźarowska, Emilia A1 - Gargouri, Hassan A1 - Henkel, Karsten A1 - Schmeißer, Dieter T1 - Aluminum nitride films prepared by plasma atomic layer deposition using different plasma sources T2 - Verhandlungen der Deutschen Physikalischen Gesellschaft, Reihe 6, Band 53,3 N2 - Aluminum nitride (AlN) thin films are promising for versatile applications in optoelectronics, electronics, piezoelectrics, and acoustics due to their remarkable properties such as wide band gap, high dielectric constant, low electrical conductivity, good piezoelectric coefficient and high ultrasonic velocity. We present a comparative study of AlN films grown by plasma-enhanced atomic layer deposition at 350°C silicon wafers in the SENTECH SI ALD LL system using TMA and NH3 where either a capacitively coupled plasma (CCP) or a direct PTSA (planar triple spiral antenna) source was applied. The films were characterized by ellipsometry, XPS and electrical measurements. The layer properties are discussed concerning the varied ALD process parameters. In general, the process using the direct PTSA source delivered films with higher refractive index and better homogeneity over the wafer achieving also higher growth rates per cycle (GPC) in reduced total cycle durations. Films with refractive index in the range of 2.05 and permittivity around 8 could be realized with a GPC of 1.54 Å/cycle. KW - Aluminium nitride KW - plasma-enhanced atomic layer deposition (PEALD) KW - ellispsometry KW - field emission scanning electron microscopy KW - atomic force microscopy KW - X-ray photoelectron spectroscopy KW - electrical characterization Y1 - 2018 SN - 0420-0195 SP - S. 170 PB - Deutsche Physikalische Gesellschaft CY - Bad Honnef ER - TY - CHAP A1 - Kot, Małgorzata A1 - Kegelmann, Lukas A1 - Kus, Peter A1 - Tsud, Nataliya A1 - Matolínová, Iva A1 - Albrecht, Steve A1 - Matolin, Vladimir A1 - Schmeißer, Dieter T1 - Room temperature atomic layer deposition for perovskite solar cells T2 - Verhandlungen der Deutschen Physikalischen Gesellschaft, Reihe 6, Band 53,3 N2 - After few years of efficiency driven research on perovskite solar cells, the focus now is shifting to understand the underlying processes governing the high efficiency and also to obtain long-term stable devices. Among various deposition methods, atomic layer deposition (ALD) may represent one of the best options, being possible to coat substrates in a very efficient way and at very low temperatures. In our previous work [1] we reported that the efficiency of the solar cell containing aged perovskite film can be enhanced twice while covering the perovskite with a thin ALD alumina film at room temperature. In this work, the chemical, electronic and morphological properties of the fresh perovskite film treated by ALD pulses of the trimethylaluminium and water at room temperature investigated using X-ray Photoelectron Spectroscopy and Field Emission Scanning Electron Microscopy will be discused and correlated with the solar cells performance and stability. [1] M. Kot et al., ChemSusChem 2016, 9, 3401. KW - Perovskite solar cells KW - atomic layer deposition KW - X-Ray photoelectron spectroscopy (XPS) KW - atomic force microscopy KW - field emission scanning electron microscopy KW - photo-conversion efficiency Y1 - 2018 SN - 0420-0195 SP - S. 174 PB - Deutsche Physikalische Gesellschaft CY - Bad Honnef ER - TY - CHAP A1 - Schmeißer, Dieter A1 - Kot, Małgorzata A1 - Corrêa, Silma Alberton A1 - Das, Chittaranjan A1 - Henkel, Karsten ED - Wandelt, Klaus T1 - Interface Potentials, Intrinsic Defects, and Passivation Mechanisms in Al₂O₃, HfO₂, and TiO₂ Ultrathin Films T2 - Encyclopedia of Interfacial Chemistry: Surface Science and Electrochemistry, vol. 3.1 N2 - We study the electronic structure of ultrathin Al₂O₃, HfO₂, and TiO₂ ALD films by resonant photoelectron spectroscopy. We identify intrinsic defects which are responsible for the active sites in interface reactions, for the incorporation of intrinsic charges, and for the formation of local dipole momenta. All of these features determine the surface potentials and the reactivity of the surface of the atomic layer deposition coated systems. We give examples of charges and dipoles in Al₂O₃, on a study of the surface potentials in HfO₂, and relate the intrinsic defects in TiO₂ to their electrochemical relevance. KW - Atomic layer deposition (ALD) KW - Resonant photoelectron spectroscopy (resPES) KW - Band scheme KW - Interface potential KW - Intrinsic charges KW - Intrinsic defects KW - Partial density of states (pDOS) KW - Exciton KW - Polaron KW - Ligand-to-metal charge transfer KW - Aluminium oxide (Al₂O₃) KW - Hafnium oxide (HfO₂) KW - Titanium Oxide (TiO₂) Y1 - 2018 SN - 978-0-12-809739-7 SN - 978-0-12-814984-3 U6 - https://doi.org/10.1016/B978-0-12-409547-2.14119-8 SP - 162 EP - 171 PB - Elsevier CY - Oxford ER - TY - GEN A1 - Biswas, Anirban A1 - Garain, Samiran A1 - Maity, Kuntal A1 - Henkel, Karsten A1 - Schmeißer, Dieter A1 - Mandal, Dipankar T1 - Influence of In situ Synthesized Bismuth Oxide Nanostructures in Self-poled PVDF-based Nanogenerator for Mechanical Energy Harvesting Application T2 - Polymer Composites N2 - A self-poled piezoelectric nanogenerator (NG) based on bismuth oxide (Bi2O3) nanostructures (BNS)-doped poly(vinylidene fluoride) (PVDF) is demonstrated. The in-situ formation of BNS incorporated in the PVDF matrix is realized through a simple solution casting technique that favors the nucleation and stabilization of 99.6% of the electroactive phase in PVDF (i.e., beta/gamma-phases). The enhancement of the output voltage (3.6 V) and current (2.4mA) of the NG based on a nonelectrically poled BNS containing PVDF composite film is achieved and demonstrated by simple repeated human finger imparting. The improvement of the output performance is influenced by the generation of the electroactive polar beta-phase in PVDF, due to the electrostatic interactions between the –CH2–/–CF2– dipoles of PVDF and the surface charge of the BNS. The NGs are able to charge up capacitors demonstrating that the power generation from such a hybrid device structure can be utilized for powering various portable devices. KW - Nanogenerators KW - energy harvesting KW - PVDF KW - bismuth oxide KW - Field-emission scanning electron microscopy (FESEM) KW - X-ray photoelectron spectroscopy (XPS) KW - X-ray diffraction (XRD) KW - Fourier Transform Infrared Spectroscopy (FTIR) Y1 - 2019 U6 - https://doi.org/10.1002/pc.24628 SN - 0272-8397 SN - 1548-0569 VL - 40 IS - S1 SP - E265 EP - E274 ER - TY - GEN A1 - Das, Chittaranjan A1 - Kot, Małgorzata A1 - Hellmann, Tim A1 - Wittich, Carolin A1 - Mankel, Eric A1 - Zimmermann, Iwan A1 - Schmeißer, Dieter A1 - Nazeeruddin, Mohammad Khaja A1 - Jaegermann, Wolfram T1 - Atomic Layer-Deposited Aluminum Oxide Hinders Iodide Migration and Stabilizes Perovskite Solar Cells T2 - Cell Reports Physical Science N2 - Iodide migration causes degradation of the perovskite solar cells. Here,we observe the direct migration of iodide into the hole-transport layer in a device. We demonstrate that ultrathin room temperature atomic layer-deposited Al2O3 on the perovskite surface very effectively hinders the migration. The perovskite-Al2O3 interface enables charge transfer across the Al2O3 layer in the solar cells, without causing any drastic changes in the properties of the perovskite absorber. Furthermore, it helps to preserve the initial properties of the perovskite film during exposure to light and air under real operating conditions, and thus, improves the stability of the solar cells. The ultrathin Al2O3 layer deposited at room temperature significantly increases the lifetime of the perovskite solar cells, and we hope this may be a step toward the mass production of stable devices. KW - perovskite solar cells KW - iodine migration KW - stability KW - X-ray photoelectron spectroscopy (XPS) KW - atomic layer deposition (ALD) KW - aluminum oxide (Al2O3) Y1 - 2020 U6 - https://doi.org/10.1016/j.xcrp.2020.100112 SN - 2666-3864 VL - 1 IS - 7 ER - TY - GEN A1 - Kot, Małgorzata A1 - Kegelmann, Lukas A1 - Köbler, Hans A1 - Vorokhta, Mykhailo A1 - Escudero, Carlos A1 - Kúš, Peter A1 - Šmíd, Břetislav A1 - Tallarida, Massimo A1 - Albrecht, Steve A1 - Abate, Antonio A1 - Matolínová, Iva A1 - Schmeißer, Dieter A1 - Flege, Jan Ingo T1 - In situ Near-Ambient Pressure X-ray Photoelectron Spectroscopy Reveals the Influence of Photon Flux and Water on the Stability of Halide Perovskite T2 - ChemSusChem N2 - For several years, scientists have been trying to understand the mechanisms that reduce the long‐term stability of perovskite solar cells. In this work, we examined the effect of water and photon flux on the stability of CH3NH3PbI3 perovskite films and solar cells using in situ near‐ambient pressure X‐ray photoelectron spectroscopy (NAP‐XPS), field emission scanning electron microscopy (FESEM), and current density–voltage (J–V) characterization. The used amount of water vapor (up to 1 mbar) had a negligible impact on the perovskite film. The higher the photon flux, the more prominent were the changes in the NAP‐XPS and FESEM data; also, a faster decline in power conversion efficiency (PCE) and a more substantial hysteresis in the J‐V characteristics were observed. Based on our results, it can be concluded that the PCE decrease originates from the creation of Frenkel pair defects in the perovskite film under illumination. The stronger the illumination, the higher the number of Frenkel defects, leading to a faster PCE decline and more substantial hysteresis in the J‐V sweeps. KW - field emission scanning electron microscopy (FESEM) KW - Frenkel defects KW - near-ambient pressure X-ray photoelectron spectroscopy (NAP-XPS) KW - perovskite KW - photon-induced degradation Y1 - 2020 U6 - https://doi.org/10.1002/cssc.202001527 SN - 1864-5631 SN - 1864-564X VL - 13 IS - 21 SP - 5722 EP - 5730 ER - TY - GEN A1 - Ghosh, Sujoy Kumar A1 - Sinha, Tridib Kumar A1 - Xie, Mengying A1 - Bowen, Christopher Rhys A1 - Garain, Samiran A1 - Mahanty, Biswajit A1 - Roy, Krittish A1 - Henkel, Karsten A1 - Schmeißer, Dieter A1 - Kim, Jin Kuk A1 - Mandal, Dipankar T1 - Temperature–Pressure Hybrid Sensing All-Organic Stretchable Energy Harvester T2 - ACS Applied Electronic Materials N2 - The design and development of intrinsically stretchable all-organic self-powered sensors concurrently perceiving temperature and pressure remain a challenge but deliver an exciting platform to realize environmentally friendly wearable electronics. In this approach, a biomimetic all-organic stretchable energy harvester is designed by a xylitol-added poly(3,4-ethylenedioxythiophene):poly(4-styrenesulfonate) (PEDOT:PSS/Xyl) film as a compatible overlay electrode with polyaniline-reinforced one-dimensional aligned poly(vinylidene fluoride) hybrid electroactive soft nanowires. The gradient of elastic modulus between the electrode and the active nanowire component enables the all-organic device to manifest excellent power-generating performance under external temperature fluctuation (∼3 μW/m2 under ΔT ∼ 92 K) and mechanical force (∼31 μW/cm2 at 30 N). Importantly, the device renders simultaneous energy scavenging of temperature and pressure changes under pressing and stretching conditions (∼20%). The excellent mechanosensitivity (∼100 mV/N), fast response time (∼1 ms), outstanding mechanical and thermal stability, and good temperature resolution <10 K enable the harvester to act as an epidermal sensor, which simultaneously detects and discriminates both subtle pressure and thermal deviations exposed to an epidermis surface. The real-time recording and wireless transferring of physiological signals to a smartphone indicate an effective way to realize remote healthcare monitoring for early intervention. KW - all-organic KW - piezoelectric KW - pyroelectric KW - energy harvester KW - sensor KW - healthcare monitoring Y1 - 2021 U6 - https://doi.org/10.1021/acsaelm.0c00816 SN - 2637-6113 VL - 3 IS - 1 SP - 248 EP - 259 ER - TY - GEN A1 - Schmeißer, Dieter A1 - Müller, Klaus A1 - Henkel, Karsten T1 - Photosensitive and Rectifying Properties of Ga2O3 Described by Polaronic Screened Electrons and Internal Potentials T2 - Journal of Physical Chemistry C N2 - The photosensitive and rectifying properties of Ga2O3 are described by (n-type) intrinsic (π-) electrons. These polaronic screened multiatomic carriers populate the intrinsic defect states within the ionic gap; their spectroscopic evidence is based on resonant photoemission spectroscopy data that also provide the ionicity factor of Ga2O3 and the size of the ionic gap. The π-electron density depends on the internal potential and its photo- and field-induced dipole contributions, and it describes the observed combined ohmic-exponential carrier densities and current–voltage dependences. The π-electron dynamics is caused by pairing and dissociation dipoles in the bulk of Ga2O3. The material properties of the electrode contribute via external chemical potentials and define the criteria for ohmic and rectifying contacts. This quantitative and predictive concept not only convinces by perfect agreement with published experimental data but also points toward the achievable performance limits of UV absorbers and rectifying devices. KW - Resonant photoelectron spectroscopy KW - quantitative π-electron densities KW - multi-atomic quasi-particles KW - photosensitivity and rectifier devices Y1 - 2023 U6 - https://doi.org/10.1021/acs.jpcc.3c05785 SN - 1932-7447 SN - 1932-7455 VL - 127 IS - 47 SP - 23077 EP - 23089 ER - TY - GEN A1 - Henkel, Karsten A1 - Oprea, A. A1 - Paloumpa, Ioanna A1 - Appel, Günter A1 - Schmeißer, Dieter A1 - Kamieth, P. T1 - Selective polypyrrole electrodes for quartz microbalances : NO2 and gas flux sensitivities T2 - Sensors and Actuators : B, Chemical 76(2001)1-3 Y1 - 2001 SN - 0925-4005 VL - 76 IS - 1-3 SP - 124 EP - 129 ER - TY - CHAP A1 - Batchelor, David R. A1 - Hoffmann, Patrick A1 - Schmeißer, Dieter A1 - Hulea, Iulian A1 - Brinza, Monica T1 - The Al-Fe interface of friction-welded joints T2 - Verhandlungen der Deutschen Physikalischen Gesellschaft N2 - The interface region of friction-welded joints Al-Fe samples is investigated by scanning Auger Spectroscopy, Electron Probe Micro-analysis (EPMA), X-ray Photoelectron spectroscopy, and Photoemission Electron Microscopy, performed at the synchrotron light source (BESSY). We investigated polished samples cut to obtain a cross-section of the Al-Fe joints. At the Al-Fe interface there is a small number of Fe teeth protuding into the adjacent Al-matrix. Beside this mechanical interlock mechanism we identify an Fe-Al alloy which is formed in an almost homogeneous interface layer of approximately 80 micron thickness. We determine the valence band spectra within that layer and notice that the alloying formation is limited to the interface region. In addition, the profile of both, the Fe and O distribution within the Al next to that interface is determined. A model of the friction-welding mechanism is derived and discussed in terms of the ability of achieving low temperature Fe-Al joints. KW - Fe-Al interface KW - friction-welded KW - X-ray photoelectron spectroscopy (XPS) KW - photoemission electron microscopy (PPEM) KW - scanning Auger spectroscopy KW - electron probe micro-analysis (EPMA) Y1 - 2000 PB - Deutsche Physikalische Gesellschaft CY - Bad Honnef ER - TY - CHAP A1 - Rachow, Fabian A1 - Hagendorf, Moritz A1 - Müller, Klaus A1 - Schmeißer, Dieter T1 - Synthesis of Methanol from CO2 for Power-to-Liquid applications T2 - Verhandlungen der Deutschen Physikalischen Gesellschaft N2 - The direct synthesis of methanol [CO2+3H2->CH3OH+H2O] represent a possibility to reduce the global CO2-emission by recycling the CO2 and also to store excess energy from renewable energy sources into a common fuel or chemical feedstock (Power-to-Liquid). For an acceptable conversion rate of CO2 a catalyst is needed, together with high temperatures (>200°C) and high pressure (50-200bar). Methanol is normally produced form synthesis gas, a mixture of CO and H2. By directly using CO2 for the exothermic reaction, we avoid the conversion of CO2 to CO by the reversed water gas shift reaction. We also present new concepts for the conversion from CO2-rich flue gases, eliminating the need for a separation of the CO2. The concept is backed up by measurements in laboratory scale. Here we use a Cu−ZnO catalyst on a ZrO2 substrate prepared by impregnation and compare the results with commercially available catalysts. We achieved a conversion of around 7% and a selectivity of 60% at a temperature of 240°C and 45bar. The reaction is thermodynamically limited with a maximum conversion rate of 15% at 250°C and 50bar. The conversion and the selectivity towards methanol is highly influenced by the catalyst used, the temperature, the pressure as well as the flow rate of the reactants. KW - direct methanol synthesis KW - power to liquide KW - Cu-ZnO catalyst KW - CO2 utilization Y1 - 2017 UR - http://www.dpg-verhandlungen.de/year/2017/conference/muenster/part/ake/session/8/contribution/5 SP - S. 256 PB - Deutsche Physikalische Gesellschaft CY - Bad Honnef ER - TY - CHAP A1 - Henkel, Karsten A1 - Kot, Małgorzata A1 - Schmeißer, Dieter T1 - Localized defect states and charge trapping in Al₂O₃ films prepared by atomic layer deposition T2 - Verhandlungen der Deutschen Physikalischen Gesellschaft N2 - The evaluation of the electronic structure and intrinsic defect mechanisms in Al₂O₃ thin films is essential for their effective use in applications with desired functionality such as surface passivation schemes for solar cells [1]. We present a comparative study of different Al₂O₃ films grown by atomic layer deposition (ALD) [2]. The layers were deposited on different substrates using the same aluminum precursor (TMA, trimethylalumium) and employing different process parameters (thermal-ALD, plasma-enhanced-ALD, substrate temperature). These films were characterized by resonant photoelectron spectroscopy and by electrical measurements (capacitance-voltage). For all films investigated intrinsic defect states within the electronic band gap were observed including excitonic, polaronic, and charge-transfer defect states, where their relative abundance is subject of the choice of ALD parameters and of the used substrate. The spectroscopic assigned in-gap defect states are related with electronic charges as determined in the electrical measurements. [1] G. Dingemans and W.M.M. Kessels, J. Vac. Sci. Technol. A 30, 040802 (2012). [2] K. Henkel, M. Kot, D. Schmeißer, J. Vac. Sci. Technol. A 35, (2017), accepted. KW - defect states KW - Al₂O₃ KW - resonant photoelectron spectroscopy KW - X-Ray absorption spectroscopy KW - capacitance-voltage measurements Y1 - 2017 UR - http://www.dpg-verhandlungen.de/year/2017/conference/dresden/part/ds/session/32/contribution/4 SN - 0420-0195 SP - S. 205 PB - Deutsche Physikalische Gesellschaft CY - Bad Honnef ER - TY - GEN A1 - Richter, Matthias R. A1 - Cheng, Wen-Hui A1 - Crumlin, Ethan J. A1 - Drisdell, Walter S. A1 - Atwater, Harry A. A1 - Schmeißer, Dieter A1 - Lewis, Nathan S. A1 - Brunschwig, Bruce S. T1 - X‑ray Photoelectron Spectroscopy and Resonant X‑ray Spectroscopy Investigations of Interactions between Thin Metal Catalyst Films and Amorphous Titanium Dioxide Photoelectrode Protection Layers T2 - Chemistry of Materials N2 - The use of electrochemistry, X-ray photoelectron spectroscopy, and resonant X-ray spectroscopy has unlocked the paradox of interfacial hole conduction through amorphous TiO2 (a-TiO2) to deposited Ni, Ir, and Au metal catalysts. Although electrocatalysts for the oxygen-evolution reaction derived from metallic Ir and Ni have mutually similar overpotentials in alkaline media, Si/a-TiO2/Ir interfaces exhibit higher overpotentials than Si/a-TiO2/Ni interfaces. The data allow formulation of full band energy diagrams for n-Si/a-TiO2/metal interfaces for M = Ni, Ir, or Au. Although both Ni and Ir produce band bending in a-TiO2 favoring hole conduction, only Ni creates multiple states within the a-TiO2 band gap at the a-TiO2/Ni interface, which produces a quasi-metallic interface at the a-TiO2/Ni junction. Au, however, produces a flat-band interface that limits hole conduction without any new band gap states. KW - X‑ray Photoelectron Spectroscopy KW - Resonant X‑ray Spectroscopy KW - titanium oxide KW - oxygen-evolution reaction KW - protection layer KW - interface interaction Y1 - 2021 U6 - https://doi.org/10.1021/acs.chemmater.0c04043 SN - 0897-4756 SN - 1520-5002 VL - 33 IS - 4 SP - 1265 EP - 1275 ER - TY - CHAP A1 - Kot, Małgorzata A1 - Wojciechowski, Konrad A1 - Snaith, Henry J. A1 - Schmeißer, Dieter T1 - Characterization of the perovskite solar cells containing atomic layer deposited Al2O3 buffer layer T2 - Verhandlungen der Deutschen Physikalischen Gesellschaft e.V. N2 - Hybrid perovskites have potential to overcome performance limits of the current solar cell technologies and achieve low cost and high versatility. Nonetheless, they are prone to degradation in presence of moisture within a couple of hours or days. In this work, we use the atomic layer deposition (ALD) of Al2O3 on the CH3NH3PbI3 perovskite at room temperature in order to verify if this thin ALD layer may protect the perovskite film against moisture degradation and to check the impact of the Al2O3 on the solar to power conversion efficiency (PCE). Depth profiling X-ray photoelectron spectroscopy study shows that the ALD precursors are chemically active only at the perovskite surface and the film bulk is not affected. The perovskite film coated with Al2O3 layer has enhanced moisture stability. Solar cells with a fresh-made CH3NH3PbI3 perovskite film have shown PCE of 15.4%, while the one with 50 days aged perovskite only 6.1%. However, when the aged perovskite is covered with RT-ALD-Al2O3 the PCE value is clearly enhanced.[1] [1] M. Kot et al., Room temperature ALD impact on efficiency, stability and surface properties in perovskite solar cells, ChemSusChem,acctepted. KW - Perovskite solar cell KW - atomic layer deposition KW - Al2O3 KW - efficiency recovery Y1 - 2017 UR - http://www.dpg-verhandlungen.de/year/2017/conference/dresden/part/cpp/session/38/contribution/5 SN - 0420-0195 SP - S. 147 PB - Deutsche Physikalische Gesellschaft CY - Bad Honnef ER - TY - CHAP A1 - Israel, Johannes A1 - Rachow, Fabian A1 - Schwiertz, Carola A1 - Charlafti, Evgenia A1 - Müller, Klaus A1 - Schmeißer, Dieter T1 - Direct CO2-Methanation of flue gas emitted by conventional power plants T2 - Verhandlungen der Deutschen Physikalischen Gesellschaft N2 - The catalytic conversion of CO2 with H2 into CH4 is possible by the Sabatier reaction CO2+4H2→CH4+2H2O. Using excess energy from renewable electricity generation, this approach offers an opportunity for recycling of CO2 as synthetic natural gas. In a new concept, we investigate the performance of the Sabatier reaction as direct methanation of flue gas, emitted by conventional power plants. We investigate the Sabatier process in an upscaled system, with a maximum input flow rate of 45 Nm3/h Gas. The performance is investigated in a simulated composition of flue gas and under real conditions at a lignite power plant in Schwarze Pumpe, Brandenburg, Germany. We can achieve a CO2-conversion of up to 90%, with approx. 100% selectivity towards CH4. Under flue gas conditions and at a certain limit of gas flow the system is operated at an autothermal running modus, a steady state equilibrium of exothermic heat production and thermal flow that needs neither external annealing nor cooling. KW - CO2 KW - methanation KW - Sabatier reaction KW - power plant KW - Schwarze Pumpe KW - autothermal mode Y1 - 2017 UR - http://www.dpg-verhandlungen.de/year/2017/conference/muenster/part/ake/session/8/contribution/5 SP - S. 255 PB - Deutsche Physikalische Gesellschaft CY - Bad Honnef ER - TY - CHAP A1 - Müller, Klaus A1 - Israel, Johannes A1 - Rachow, Fabian A1 - Schmeißer, Dieter ED - Ramirez Reina, Tomas ED - Odriozola, José Antonio ED - Arellano-Garcia, Harvey T1 - Sabatier-Based Direct Synthesis of Methane and Methanol Using CO2 from Industrial Gas Mixtures T2 - Engineering Solutions for CO2 Conversion KW - Sabatier reaction KW - CO2 emission reduction KW - industrial CO2 sources Y1 - 2021 SN - 978-3-527-34639-4 SP - 253 EP - 280 PB - Wiley-VCH CY - Weinheim ET - 1 ER - TY - GEN A1 - Mahmoodinezhad, Ali A1 - Janowitz, Christoph A1 - Naumann, Franziska A1 - Plate, Paul A1 - Gargouri, Hassan A1 - Henkel, Karsten A1 - Schmeißer, Dieter A1 - Flege, Jan Ingo T1 - Low-temperature growth of gallium oxide thin films by plasma-enhanced atomic layer deposition T2 - Journal of Vacuum Science and Technology A N2 - Gallium oxide (Ga2O3) thin films were deposited by plasma-enhanced atomic layer deposition (PEALD) applying a capacitively coupled plasma source where trimethylgallium (TMGa) as the gallium precursor and oxygen (O2) plasma were used in a substrate temperature (Ts)in the range of 80–200 °C. TMGa exhibits high vapor pressure and therefore facilitates deposition at lower substrate temperatures. The Ga2O3 films were characterized by spectroscopic ellipsometry (SE), x-ray photoelectron spectroscopy (XPS), and capacitance-voltage (C-V) measurements. The SE data show linear thickness evolution with a growth rate of ∼0.66 Å per cycle and inhomogeneity of ≤2% for all samples. The refractive index of the Ga2O3 thin films is 1.86 ± 0.01 (at 632.8 nm) and independent of temperature, whereas the bandgap slightly decreases from 4.68 eV at Ts of 80 °C to 4.57 eV at 200 °C. XPS analysis revealed ideal stoichiometric gallium to oxygen ratios of 2:3 for the Ga2O3 layers with the lowest carbon contribution of ∼10% for the sample prepared at 150 °C. The permittivity of the layers is 9.7 ± 0.2 (at 10 kHz). In addition, fixed and mobile oxide charge densities of 2–4E12 and 1–2E12 cm−2, respectively, were observed in the C-V characteristics. Moreover, the Ga2O3 films show breakdown fields in the range of 2.2–2.7 MV/cm. Excellent optical and electrical material properties are maintained even at low substrate temperatures as low as 80 °C. Hence, the TMGa/O2 PEALD process is suitable for electronic and optoelectronic applications where low-temperature growth is required. KW - Plamsa enhanced atomic layer deposition (PEALD) KW - low-temperature growth KW - gallium oxide (Ga2O3) KW - x-ray photoelectron spectroscopy KW - spectroscopic ellipsometry KW - capacitance voltage measurements Y1 - 2020 U6 - https://doi.org/10.1116/1.5134800 SN - 0734-2101 SN - 1520-8559 VL - 38 IS - 2 ER - TY - GEN A1 - Maity, Kuntal A1 - Garain, Samiran A1 - Henkel, Karsten A1 - Schmeißer, Dieter A1 - Mandal, Dipankar T1 - Self-Powered Human-Health Monitoring through Aligned PVDFNanofibers Interfaced Skin-Interactive Piezoelectric Sensor T2 - ACS Applied Polymer Materials N2 - Flexible and wearable e-skin sensors are attracting a great interest for their smart sensing applications in next-generation electronics. However, implant ability, sensitivity, and biosignal detection capability in a self-powered manner are the prime concerns in embedded devices. In particular, electrode compatibility and imperishability have become challenging issues in wearable sensors due to the poor compatibility and fragileness of metal electrodes. In this context, we report on a skin-interactive metal-free spongy electrode in a piezoelectric sensor where highly aligned poly(vinylidenefluoride) (PVDF) nanofibers (NFs) arrays are introduced as the piezoelectric active component and conducting polyaniline- (PANI-) coated PVDF (PANI−PVDF) NFs mats served as flexible electrodes. Notably, a 99% yield of piezoelectric phases of the aligned PVDF arrays is the key factor to exhibit promising mechano-sensitivity (0.8 V/kPa) performance that in turn helps in human-health monitoring. The sensor shows excellent mechanical to electrical energy conversion that enable to sense human finger touch (10 V under 10 kPa) with energy conversion efficiency of 53%. Most importantly, due to the compatible electrodes excellent mechanical stability has been found showing negligible degradation over 12,000 periodic cycles. Furthermore, under mechanical stimuli, it is also possible to charge up a capacitor (1μF) to 4 V within 60 s confirming the possibility to use the device as a self-powered piezo-organic-e-skin sensor (POESS). This type of structural design enables to trace elusive movement of muscles and the operation in several conditions such as bending, compression and stretching. We demonstrated various human gestures monitoring, such as wrist bending, neck stretching, and arm compressions, throat movements during drinking water, coughing actions, and swallowing. In addition, diverse specific phonation recognition, heart-pulse measurement and its respective short-time Fourier transform (STFT) analysis indicate an efficient and convenient way of monitoring human-health status particularly in hospital-free mode. KW - e-skin sensor KW - piezoelectric nanofibers KW - PVDF KW - flexible electrode KW - health-care monitoring KW - self-powered electronics Y1 - 2020 U6 - https://doi.org/10.1021/acsapm.9b00846 SN - 2637-6105 VL - 2 IS - 2 SP - 862 EP - 878 ER - TY - GEN A1 - Kot, Małgorzata A1 - Vorokhta, Mykhailo A1 - Wang, Zhiping A1 - Snaith, Henry J. A1 - Schmeißer, Dieter A1 - Flege, Jan Ingo T1 - Thermal stability of CH3NH3PbIxCl3-x versus [HC(NH2)2]0.83Cs0.17PbI2.7Br0.3 perovskite films by X-ray photoelectron spectroscopy T2 - Applied Surface Science N2 - The thermal stability of CH3NH3PbIxCl3-x and [HC(NH2)2]0.83Cs0.17PbI2.7Br0.3 perovskite films was studied in-situ by X-ray photoelectron spectroscopy. It was found that below 85 °C both of them are relatively stable. After annealing above 85 °C, we observe a clear perovskite surface decomposition, i.e., a release of organic cations and creation of “metallic lead”. The mixed cation lead mixed halide perovskite, however, decomposes at a much lower rate. For both perovskite films, the metallic to the total lead ratio changes with the same rate for the same annealing temperatures. The release of A-site cations from the ABX3 crystal structure of perovskite and/or creation of “metallic lead” causes also a small shift of the valence band maximum towards the Fermi level. The release of [HC(NH2)2]± or Cs± is not as significant as the release of CH3NH3±; therefore, it may explain why [HC(NH2)2]0.83Cs0.17PbI2.7Br0.3 solar cells are thermally more stable. Therefore, as the stability of CH3NH3PbIxCl3-x is same as the stability of [HC(NH2)2]0.83Cs0.17PbI2.7Br0.3 below 85 °C, there must be more severe degradation pathways that are currently underappreciated on the solar cell level. KW - Hybrid organic inorganic perovskite solar cells KW - X-ray photoelectron spectroscopy KW - Film degradation KW - Thermal stability Y1 - 2020 U6 - https://doi.org/10.1016/j.apsusc.2020.145596 SN - 0169-4332 SN - 1873-5584 VL - 513 ER - TY - GEN A1 - Kot, Małgorzata A1 - Henkel, Karsten A1 - Naumann, Franziska A1 - Gargouri, Hassan A1 - Tarnawska, Lidia Lupina A1 - Wilker, Viola A1 - Kus, Peter A1 - Pożarowska, Emilia A1 - Garain, Samiran A1 - Rouissi, Zied A1 - Schmeißer, Dieter T1 - Comparison of plasma-enhanced atomic layer deposition AlN films prepared with different plasma sources T2 - Journal of Vacuum Science and Technology A N2 - A comparative study of thin aluminum nitride (AlN) films deposited by plasma-enhanced atomic layer deposition in the SENTECH SI ALD LL system applying either a direct inductively coupled plasma (ICP) or an indirect capacitively coupled plasma (CCP) source is presented. The films prepared with the ICP source (based on a planar triple spiral antenna) exhibit improved properties concerning the growth rate per cycle, total cycle duration, homogeneity, refractive index, fixed and mobile electrical charges, and residual oxygen content compared to the CCP source, where the comparison is based on the applied plasma power of 200 W. The increase of the plasma power to 600 W in the ICP process significantly reduces the residual oxygen content and enhances the electrical breakdown field. The AlN layers grown under these conditions, with a growth rate per cycle of 1.54 Å/cycle, contain residual oxygen and carbon concentrations of about 10% and 4%, respectively, and possess a refractive index of 2.07 (at 632.8 nm). KW - Plamsa-enhanced atomic layer deposition (PEALD) KW - inductively coupled KW - capacitively coupled KW - plamsa source KW - ellipsometry KW - X-ray photoelectron spectroscopy (XPS) KW - X-ray diffraction (XRD) KW - Field emission scanning electron microscopy (FESEM) KW - capacitance-voltage (CV) KW - atomic force microscopy Y1 - 2019 U6 - https://doi.org/10.1116/1.5079628 SN - 0734-2101 SN - 1520-8559 VL - 37 IS - 2 ER - TY - GEN A1 - Kotwica, Tomasz A1 - Domaradzki, Jarosław A1 - Wojcieszak, Damian A1 - Sikora, Andrzej A1 - Kot, Małgorzata A1 - Schmeißer, Dieter T1 - Analysis of surface properties of Ti-Cu-Ox gradient thin films using AFM and XPS investigations T2 - Materials Science-Poland N2 - The paper presents results of investigations on surface properties of transparent semiconducting thin films based on (Ti-Cu)oxide system prepared using multi-magnetron sputtering system. The thin films were prepared using two programmed profiles of pulse widt hmodulation coefficient, so called V- and U-shape profiles. The applied powering profiles allowed fabrication of thin films with gradient distribution of Ti and Cu elements over the thickness of deposited layers. Optical investigations allowed determination of transparency of prepared films that reached up to 60 % in the visible part of optical radiation, which makes them attractive for the transparent electronics domain. Surface properties investigations showed that the surface of mixed (Ti-Cu)oxides was sensitive to adsorption, in particular to carbon dioxide and water vapor. Soft etching with argon ions resulted in surface cleaning from residuals, however, deoxidation of Cu-oxide components was also observed. KW - surface KW - gradient distribution KW - thin film oxide Y1 - 2019 U6 - https://doi.org/10.2478/msp-2018-0100 SN - 0137-1339 SN - 2083-1331 SN - 2083-134X VL - 36 IS - 4 SP - 761 EP - 768 ER - TY - GEN A1 - Janowitz, Christoph A1 - Schmeißer, Dieter T1 - Out-of-plane electronic contributions in Bi-cuprates studied by resonant photoelectron spectroscopy at the Cu 2p edge T2 - Verhandlungen der DPG N2 - In high-temperature superconductors with a layered crystal structure out-of-plane contributions are often neglected, while the copper-oxygen planes are commonly considered to dominate the electronic properties around the Fermi energy. Here we report on a resonant photoemission study of (Pb,Bi)2201 and (Pb,Bi)2212 single crystals to unravel the resonant decay mechanisms at the Cu 2p absorption edge. We demonstrate a pronounced polarization dependence caused by two different Auger processes for in-plane and out-of-plane orientations. We deduce that the lowest energy valence state being involved in the two Auger processes, consists of three-dimensional contributions by admixed out-of-plane Sr, Bi, and O 2p states. It also suggests that the doping-induced charge density is dynamic, fluctuating within the Cu-O plane, and spills out perpendicular to it. C. Janowitz and D. Schmeißer, Supercond. Sci. Technol. 31, 045006 (2018) KW - high-temperature superconductors KW - resonant photoemission spectroscopy KW - single crystal KW - doping-induced charge density Y1 - 2019 UR - https://www.dpg-verhandlungen.de/year/2019/conference/regensburg/part/tt/session/49/contribution/19 SN - 0420-0195 SP - 403 EP - 403 PB - Deutsche Physikalische Gesellschaft CY - Bad Honnef ER - TY - GEN A1 - Mahmoodinezhad, Ali A1 - Pożarowska, Emilia A1 - Henkel, Karsten A1 - Schmeißer, Dieter A1 - Flege, Jan Ingo T1 - Depth profiling of PEALD-AlN films based on Al2p XPS peak decomposition T2 - Verhandlungen der DPG N2 - AlN has remarkable properties (wide band gap, low electrical and thermal conductivity, high dielectric constant, piezoelectricity) and is attractive for (opto)electronic and sensor applications. However, high oxygen content within nitride films is always a critical issue due to the thermodynamically favorable oxidation against nitridation resulting in deteriorated materials properties. In order to clarify whether the oxidation is a surface-limited or a bulk process elemental depth profiling is essential. In this work XPS in combination with Ar+ sputtering is applied to carry out depth profiling of AlN films prepared by plasma-enhanced atomic layer deposition using different parameters (plasma source, power and pulse duration). Particularly, the Al2p core levels are analyzed where the signals are decomposed into four components, representing weaker contributions of pure AlN and aluminum oxide phases as well as stronger signals of mixed oxygen-rich and nitrogen-rich phases. After sputtering (providing access to the deeper part of the film) the pure AlN phase content increases while the pure aluminum oxide content stays relatively constant. These issues are discussed with regard to the preparation parameters employed and accompanying XRD and electrical measurements. KW - X-Ray photoelectron spectroscopy (XPS) KW - peak decomposition KW - plasma enhanced atomic layer deposition (PEALD) KW - aluminium nitride (AlN) Y1 - 2019 UR - https://www.dpg-verhandlungen.de/year/2019/conference/regensburg/part/ds/session/14/contribution/25 SN - 0420-0195 SP - 157 EP - 157 PB - Deutsche Physikalische Gesellschaft CY - Bad Honnef ER - TY - GEN A1 - Obstarczyk, Agata A1 - Kaczmarek, Danuta A1 - Wojcieszak, Damian A1 - Mazur, Michał A1 - Domaradzki, Jarosław A1 - Kotwica, Tomasz A1 - Pastuszek, Roman A1 - Schmeißer, Dieter A1 - Mazur, Piotr A1 - Kot, Małgorzata T1 - Tailoring optical and electrical properties of thin-film coatings based on mixed Hf and Ti oxides for optoelectronic application T2 - Materials and Design N2 - In this work multi-magnetron sputtering stand was used for the deposition of the mixed oxides thin films based on HfO2 and TiO2. In order to obtain various material composition the power released to each magnetron (containing metallic hafnium and titanium targets) was precisely selected. Structural, surface, optical, electrical and mechanical properties of as-deposited coatings were analyzed. Depending on the hafnium content in the deposited thin films various types of the microstructure was obtained, i.e. HfO2-monoclinic, amorphous and TiO2-rutile. Increase of Ti content above 28 at. % in the as-prepared mixed oxides coatings caused their amorphization. It was found that with an increase of Ti content in prepared coatings their surface roughness and simultaneously water contact angle decreased. Performed measurements of electrical properties revealed that the lowest leakage current density in the range of 10−7 – 10−8 A/cm2 was obtained for amorphous coatings. Moreover, the tailoring of the dielectric constant was possible by a proper selection of material composition and microstructure of the deposited thin films. Average transparency in the visible wavelength region was in the range of ca. 79–86%. The influence of material composition and structure on shifting of the fundamental absorption edge and optical bandgap energy was also observed. The refractive index increased with an increase of Ti content, while extinction coefficient was the lowest for amorphous coatings. Additionally, hardness values were dependent on the material composition and optical packing density and were in the range from 7.6 GPa to 10.1 GPa. KW - Magnetron sputtering KW - Optical coatings KW - Electrical properties KW - Mixed oxides KW - HfO2 KW - TiO2 KW - High-k oxides KW - Amorphous thin films Y1 - 2019 U6 - https://doi.org/10.1016/j.matdes.2019.107822 SN - 0264-1275 VL - 175 ER - TY - GEN A1 - Roy, Krittish A1 - Ghosh, Sujoy Kumar A1 - Sultana, Ayesha A1 - Garain, Samiran A1 - Xie, Mengying A1 - Bowen, Christopher Rhys A1 - Henkel, Karsten A1 - Schmeißer, Dieter A1 - Mandal, Dipankar T1 - A Self-Powered Wearable Pressure Sensor and Pyroelectric Breathing Sensor Based on GO Interfaced PVDF Nanofibers T2 - ACS Applied Nano Materials N2 - This paper reports a self-powered,flexible, piezo- and pyro-electric hybrid nanogenerator (NG) device that can be fixed on different locations of human skin for detecting static and dynamic pressure variations and can also monitor temperature fluctuations during the respiration process. An efficient and cost-effective fabrication strategy has been developed to create electrospun poly(vinylidene fluoride) (PVDF)/graphene oxide (GO) nanofibers, which are used to create a highly sensitive wearable pressure sensor and pyroelectric breathing sensor. The sensor can accurately and rapidly detect pressures as low as 10 Pa with a high sensitivity (4.3 V/kPa), a key performance indicator for wearable sensors. Importantly, the sensor exhibits a high sensitivity to bending and stretching by finger, wrist, and elbow. The pressure sensor is also highly sensitive to vocal vibrations when attached to the human throat. The device can generate a maximum output power density of∼6.2 mW/m2 when subjected to a compressive stress, which enhances its range of applications. Moreover, it is demonstrated that doping with GO improves the pyroelectric energy harvesting and sensing performance of the device under repeated temperature fluctuations. The PVDF/GO-based nanogenerator has a maximum pyroelectric output power density of∼1.2 nW/m2 and can sense temperature changes during respiration, which makes it promising as a pyroelectric breathing sensor. It is demonstrated that processing of the PVDF-GO self-powered multifunctional pressure and pyroelectric breathing sensor can be up-scaled for fabricating compact and high-performance electronic skins for application in health monitoring, motion detection, and portable electronics. KW - piezo- and pyro-electric hybrid nanogenerator KW - poly(vinylidenefluoride) (PVDF)/graphene oxide (GO) nanofibers KW - wearable pressure sensor KW - breathing sensor Y1 - 2019 U6 - https://doi.org/10.1021/acsanm.9b00033 SN - 2574-0970 VL - 2 IS - 4 SP - 2013 EP - 2025 ER - TY - GEN A1 - Müller, Klaus A1 - Rachow, Fabian A1 - Günther, Vivien A1 - Schmeißer, Dieter T1 - Methanation of Coke Oven Gas with Nickel-based catalysts T2 - International Journal of Environmental Science N2 - For a complete transition from fossil to CO₂ neutral energy supply new energy storage concepts are needed that allow energy supply in times of absence of regenerative power production as during dark doldrums. A promising renewable energy storage approach is the power to gas (to power) technique based on the production of synthetic natural gas (also called e-methane) by methanation of CO₂ with H₂. The latter is usually produced by electrolysis. In any power to gas concept, electrolysis is a very critical part, due to its high costs, stability issues, or limited power of required electrolysers. As an alternative source of hydrogen, we investigate the methanation of coke oven gas (COG). COG is a byproduct of the carbon rich coke production from coal for the steel industry, with a high amount of hydrogen (~60vol%). Coke oven gas furthermore contains CH₄(~25vol%), CO (5-8vol%), and CO₂(1-3vol%), making it an attractive feedstock for the production of synthetic energy carriers like methane. In the present study, the authors investigate the direct conversion of CO and CO₂ from COG into e-methane. Compared to stoichiometric conversion, the COG hydrogen content is too high for catalytic methanation of CO₂. In order to achieve a higher methane yield, the addition of CO₂ from air, flue gas, or coal gasification can compensate the surplus of hydrogen in the coke oven gas. The process is evaluated by the conversion of CO and CO₂, the catalyst selectivity towards higher hydrocarbons for varying temperatures, and the CH₄ yield. KW - Coke Oven Gas KW - CO₂ recycling KW - Power to Gas (PtG) KW - Synthetic Natural Gas (SNG) KW - e-methane KW - Sabatier-Reaction Y1 - 2019 UR - https://www.iaras.org/iaras/home/caijes/methanation-of-coke-oven-gas-with-nickel-based-catalysts UR - https://iaras.org/iaras/filedownloads/ijes/2019/008-0009(2019).pdf SN - 2367-8941 IS - 4 SP - 73 EP - 79 ER - TY - GEN A1 - Kot, Małgorzata A1 - Henkel, Karsten A1 - Müller, Klaus A1 - Kegelmann, Lukas A1 - Albrecht, Steve A1 - Tsud, Nataliya A1 - Kús, Peter A1 - Matolinová, Iva A1 - Schmeißer, Dieter T1 - Al2O3-Atomic Layer Deposited Films on CH3NH3PbI3 : Intrinsic Defects and Passivation Mechanisms T2 - Energy Technology , The Journal of Physical Chemistry C N2 - The initial interaction of atomic layer deposited films of Al2O3 at room temperature on CH3NH3PbI3 (MAPI) films is studied. Synchrotron radiation–based photoelectron spectroscopy is applied to analyze the initial changes in the Al-derived features by comparing samples with different Al2O3 film thicknesses. It is found that polarons and excitons, both intrinsic defects of Al2O3, play a key role in the interface formation. The polaronic states uptake a charge from the MAPI substrate. This charge is transferred to and stabilized in the excitonic state of Al2O3 which is assigned to predominately tetrahedral coordinated Al sites. This charge transfer is initiated by vacancies present in the MAPI substrate and stabilizes a covalent bonding at the Al2O3–MAPI interface but also causes a roughening of the interface which may lead to the formation of grain boundaries. On top of the rough interface, 2D Al2O3 clusters with an increasing number of octahedrally coordinated Al—O bonds grow, and with increasing Al2O3 coverage, they introduce self-healing of the structural defects. KW - charge donation and transfer cycles KW - covalent interfaces KW - defect monitoring KW - model of Al2O3–CH3NH3PbI3 interactions KW - resonant photoelectron spectroscopy Y1 - 2019 U6 - https://doi.org/10.1002/ente.201900975 SN - 2194-4288 SN - 2194-4296 VL - 7 IS - 11 ER - TY - GEN A1 - Schmeißer, Dieter A1 - Henkel, Karsten A1 - Pożarowska, Emilia A1 - Kegelmann, Lukas A1 - Tsud, Nataliya A1 - Kot, Małgorzata T1 - Point Defect-Mediated Interface Formation and Appearance of a Cooper Minimum for AlOₓ Atomic-Layer-Deposited Films on CH₃NH₃PbI₃ T2 - The Journal of Physical Chemistry. C N2 - We report on the interaction of CH₃NH₃PbI₃ substrates with AlOx films prepared by atomic layer deposition at room temperature. We use synchrotron radiation-based photoemission spectroscopy and study the Pb 4f, I 3d, and Al 2p core levels as well as the corresponding valence band states (Pb 5d and O 2p). A Cooper minimum is observed for both the Pb 5d and O 2p states, and it indicates that the bonding at the interface must be covalent. We focus on the electronic properties of the substrate and its interface and identify a delicate charge balance between polaronic and excitonic states in MAPI and AlOₓ. The perovskite vacancy sites, identified by changes in the core-level intensities, mediate the charge balance and covalent interaction. KW - Resonant photoelectron spectroscopy KW - Al₂O₃-CH₃NH₃PbI₃ interaction KW - Cooper minimum KW - point defects in CH₃NH₃PbI₃ KW - electronic structure of CH₃NH₃PbI₃ Y1 - 2019 U6 - https://doi.org/10.1021/acs.jpcc.9b05282 SN - 1932-7447 SN - 1932-7455 VL - 123 IS - 38 SP - 23352 EP - 23360 ER - TY - GEN A1 - Schmeißer, Dieter A1 - Henkel, Karsten T1 - Intrinsic defects and multiple-atom processes in the oxidic semiconductor Ga₂O₃ T2 - Journal of Applied Physics N2 - We report on the electronic structure of gallium oxide (Ga₂O₃) single crystals as studied by resonant photoelectron spectroscopy (resPES). We identify intrinsic electronic defects that are formed by mixed-atomic valence states. We differentiate three coexisting defect states that differ in their electronic correlation energy and their spatial localization lengths. Their relative abundance is described by a fractional ionicity with covalent and ionic bonding contributions. For Ga₂O₃, our analyses of the resPES data enable us to derive two main aspects: first, experimental access is given to determine the ionicity based on the original concepts of Pauling and Phillips. Second, we report on multi-atomic energy loss processes in the Ga2p core level and X-ray absorption data. The two experimental findings can be explained consistently in the same context of mixed-atomic valence states and intrinsic electronic defects. KW - resonat photoelectron spectroscopy (resPES) KW - X-Ray absorption KW - gallium oxide (Ga₂O₃) KW - intrinsic electronic defects KW - band scheme Y1 - 2018 U6 - https://doi.org/10.1063/1.5010740 SN - 0021-8979 SN - 1089-7550 VL - 123 IS - 16 SP - 161596-1 EP - 161596-9 ER - TY - GEN A1 - Dorp, Dennis H. von A1 - Nyns, Laura A1 - Cuypers, Daniel A1 - Ivanov, Tsvetan A1 - Brizzi, Simone A1 - Tallarida, Massimo A1 - Fleischmann, Claudia A1 - Hönicke, Philipp A1 - Müller, Matthias A1 - Richard, Olivier A1 - Schmeißer, Dieter A1 - De Gendt, Stefan A1 - Lin, Dennis H. C. A1 - Adelmann, Christoph T1 - Amorphous Gadolinium Aluminate as a Dielectric and Sulfur for Indium Phosphide Passivation T2 - ACS Applied Electronic Materials N2 - The passivation of n-type InP (100) using sulfur in combination with a gadolinium aluminate (GAO) dielectric layer has been studied. Photoluminescence, minority-carrier lifetime, and capacitance−voltage measurements indicate that a (NH4)2S vapor passivation step prior to atomic layer deposition of the oxide effectively lowers the interface state density. Surface and interface chemistry were studied by synchrotron radiation photoemission spectroscopy (SRPES). The effect of ex situ surface passivation after native oxide removal in HCl solution was examined. It was observed that surface reoxidation occurred during (NH4)2S vapor exposure, leading to the formation of Inx(HPO4)y. S was present on the surface as a sulfide in both surface and subsurface sites. After atomic layer deposition of GAO, sulfates were detected in addition to Inx(HPO4)y, which was confirmed by near-edge X-ray absorptionfine structure analysis. The S in the stack was quantified using reference-free grazing incidence X-rayfluorescence analysis. X-ray absorption spectroscopy showed that Gd was oxidized and present in the 3+ oxidation state, most likely as a phosphate close to the InP interface and possibly mixed with sulfates. Energy-dependent SRPES measurements of Al 2p and Gd 4d core levels, complemented by transmission electron microscopy, further suggest that the dielectric layer was segregated. Valence band measurements confirm the effective passivation of InP, indicating unpinning of the surface Fermi level. KW - III−V KW - InP KW - sulfur passivation KW - atomic layer deposition KW - gadolinium aluminate KW - rare earth oxide KW - dielectric Y1 - 2019 U6 - https://doi.org/10.1021/acsaelm.9b00388 SN - 2637-6113 VL - 1 IS - 11 SP - 2190 EP - 2201 ER - TY - GEN A1 - Janowitz, Christoph A1 - Schmeißer, Dieter T1 - Significance of out-of-plane electronic contributions in Bi-cuprates studied by resonant photoelectron spectroscopy at the Cu2p-edge T2 - Superconductor Science and Technology N2 - In high-temperature superconductors with a layered crystal structure, the copper–oxygen planes are commonly considered to dominate the electronic properties around the Fermi energy. As a consequence, out-of-plane contributions are often neglected in the description of these materials. Here we report on a resonant photoemission study of Pb₀,4Bi1,₆Sr₂,₀CaCu₂0₈ ((Pb, Bi)-2212) and Pb₀,₆Bi₁,₄Sr₁.5La₀.5Cu0₆ ((Pb, Bi)-2201)) single crystals to unravel the resonant decay mechanisms at the Cu2p absorption edge. We find evidence for a pronounced polarization dependence caused by two different Auger processes for in-plane and out-of-plane orientations. We deduce that the lowest energy valence state—which is involved in the two Auger processes—consists of three-dimensional contributions by admixed out-of-plane Sr, Bi, and 02p states. It also suggests that the doping-induced charge density is dynamic, fluctuating within the Cu–0 plane, and spills out perpendicular to it. This suggests that out-of-plane electronic degrees of freedom should be included in future consistent theoretical models of these materials. KW - synchrotron radiation KW - polarization dependence KW - 3D hole doping KW - superconductor Y1 - 2018 U6 - https://doi.org/10.1088/1361-6668/aaadf6 SN - 0953-2048 SN - 1361-6668 VL - 31 IS - 4 ER - TY - GEN A1 - Kot, Małgorzata A1 - Łobaza, Justyna A1 - Naumann, Franziska A1 - Gargouri, Hassan A1 - Henkel, Karsten A1 - Schmeißer, Dieter T1 - Long-term ambient surface oxidation of titanium oxynitride films prepared by plasma-enhanced atomic layer deposition: An XPS study T2 - Journal of Vacuum Science and Technology A N2 - The surface oxidation of a titanium oxynitride (TiOxNy) film after long-time storage of 25 month in ambient conditions is investigated. The TiOxNy film is prepared by plasma-enhanced atomic layer deposition using etrakis(dimethylamino)titanium and nitrogen plasma, and the film is characterized by Ar+ ion sputtering of the film surface in combination with x-ray photoelectron spectroscopy (XPS) as well as by angle-resolved XPS. The total thickness of an oxygen-enriched layer at the surface of the TiOxNy films is found to be about 0.7 nm and it consists of a sequence of a 0.4 nm thick TiON/TiO2 enriched layer followed by a 0.3 nm thick TiO2 enriched layer underneath compared to the bulk composition of the film which shows constant values of 29% TiN, 29% TiO2, and 42% TiON. The results suggest that the TiON enrichment takes place initially at the surface followed by a surface and subsurface oxidation. KW - atomic layer deposition (ALD) KW - surface oxidation KW - X-Ray photoelectron spectroscopy (XPS) KW - titanium oxynitride Y1 - 2018 U6 - https://doi.org/10.1116/1.5003356 SN - 0734-2101 SN - 1520-8559 VL - 36 IS - 1 ER - TY - GEN A1 - Garain, Samiran A1 - Sen, Shrabanee A1 - Henkel, Karsten A1 - Schmeißer, Dieter A1 - Mandal, Dipankar T1 - Enhancement of Electroactive β-phase and Superior Dielectric Properties in Cerium Based Poly(vinylidene fluoride) Composite Films T2 - Materials Today: proceedings N2 - In this work we report on the preparation of poly(vinylidene fluoride) (PVDF) films with various mass fractions (wt%) of hydrated rare earth metal salt [(NH4)4Ce(SO4)4.2H2O] (CAS) and its electroactive phase (β- and γ-phase) formation. It was found that CAS can yield high amount of electroactive phases in PVDF. Compared to the neat PVDF film, a significantly increment of dielectric constant (ε ∼ 41) and a low loss factor (tan δ ∼ 0.8) were observed in the PVDF-CAS composite films. Thus the PVDF-CAS composite films with high electroactive phase and superior dielectric properties may meet the requirements of next generation electronic components. KW - PVDF KW - High amount of electroactive phase KW - Superior dielectric properties Y1 - 2018 U6 - https://doi.org/10.1016/j.matpr.2017.11.003 SN - 2214-7853 VL - 5 IS - 3 part 3 SP - 10084 EP - 10090 ER - TY - GEN A1 - Kot, Małgorzata A1 - Wojciechowski, Konrad A1 - Snaith, Henry J. A1 - Schmeißer, Dieter T1 - Evidence of Nitrogen Contribution to the Electronic Structure of the CH₃NH₃PbI₃ Perovskite T2 - Chemistry - A European Journal N2 - Despite fast development of hybrid perovskite solar cells, there are many fundamental questions related to the perovskite film which remain open. For example, there are contradicting theoretical reports on the role of the or-ganic methylammonium cation (CH₃NH₃+)in the methylam-monium lead triiodide (CH₃NH₃PbI₃)perovskite film. From one side it is reported that the organic cation does not contribute to electronic structure of the CH₃NH₃PbI₃ film. From the other side, valence band maximum fluctuations, dependent on the CH₃NH₃+ rotation, have been theoretically predicted. The resonant X-ray photoelectron spectroscopy results reported here show experimental evidence of nitrogen contribution to the CH₃NH₃PbI₃ electronic structure. Moreover,the observed strong resonances of nitrogen with the I 5s and the Pb 5d-6s levels indicate that the CH₃NH₃PbI₃ valence band is extended up to ~18 eV below the Fermi energy, and therefore one should also consider these shallow core levels while modeling its electronic structure. KW - methylammonium lead triiodide (CH₃NH₃PbI₃) KW - electronic structure KW - perovskite solar cells KW - resonant X-ray photoelectron spectroscopy (resPES) Y1 - 2018 U6 - https://doi.org/10.1002/chem.201705144 SN - 0947-6539 SN - 1521-3765 VL - 24 IS - 14 SP - 3539 EP - 3544 ER - TY - CHAP A1 - Henkel, Karsten A1 - Kot, Małgorzata A1 - Richter, Matthias A1 - Tallarida, Massimo A1 - Schmeißer, Dieter ED - Wandelt, Klaus T1 - An (In Situ)² Approach: ALD and resPES Applied to Al₂O₃, HfO₂, and TiO₂ Ultrathin Films T2 - Encyclopedia of Interfacial Chemistry: Surface Science and Electrochemistry, Vol. 3.1 N2 - Oxide surface coatings are of importance in tailoring interface properties with respect to surface passivation, adjustment of surface potentials, or providing active centers for surface reactions. In this contribution, we report about surface coatings prepared by the atomic layer deposition (ALD) method. ALD is known for its conformal growth of ultrathin, dense films which exhibit a low concentration of pinholes. KW - Atomic layer deposition (ALD) KW - Resonant photoelectron spectroscopy (resPES) KW - Band scheme KW - Partial density of states (pDOS) KW - Intrinsic charges KW - Intrinsic defects KW - Aluminum oxide (Al₂O₃) KW - Hafnium oxide (HfO₂) KW - Titanium oxide(TiO₂) Y1 - 2018 SN - 978-0-12-809739-7 SN - 978-0-12-809894-3 U6 - https://doi.org/10.1016/B978-0-12-409547-2.13852-1 SP - 18 EP - 26 PB - Elsevier CY - Oxford ER - TY - GEN A1 - Maity, Kuntal A1 - Garain, Samiran A1 - Henkel, Karsten A1 - Schmeißer, Dieter A1 - Mandal, Dipankar T1 - Natural Sugar-Assisted, Chemically Reinforced, Highly Durable Piezoorganic Nanogenerator with Superior Power Density for Self-Powered Wearable Electronics T2 - ACS Applied Materials & Interfaces N2 - Natural piezoelectric materials are of increasing interest, particularly for applications in biocompatible, implantable, and flexible electronic devices. In this paper, we introduce a cost-effective, easily available natural piezoelectric material, that is, sugar in the field of wearable piezoelectric nanogenerators (PNGs) where low electrical output, biocompatibility, and performance durability are still critical issues. We report on a high-performance piezoorganic nanogenerator (PONG) based on the hybridization of sugar-encapsulated polyvinylidenefluoride (PVDF) nanofiber webs (SGNFW). We explore the crucial role of single-crystal sugar having a fascinating structure along with the synergistic enhancement of piezoelectricity during nanoconfinement of sugar-interfaced macromolecular PVDF chains. As a consequence, the SGNFW-based PONG exhibits outstanding electricity generation capability (e.g.,∼100 V under 10 kPa human finger impact and maximum power density of 33 mW/m2) in combination with sensitivity to abundantly available different mechanical sources (such as wind flow, vibration, personal electronics, and acoustic vibration). Consequently, it opens up suitability in multifunctional self-powered wearable sensor designs for realistic implementation. In addition, commercially available capacitors are charged up effectively by the PONG because of its rapid energy storage capability. The high performance of the PONG not only offers“battery-free”energy generation (several portable units of light-emitting diodes and a liquid crystal display screen are powered up without using external storage) but also promises its use in wireless signal transmitting systems, which widens the potential in personal health care monitoring. Furthermore, owing to the geometrical stress confinement effect, the PONG is proven to be a highly durable power-generating device validated by stability test over 10 weeks. Therefore, the organic nanogenerator would be a convenient solution for portable personal electronic devices that are expected to operate in a self-powered manner. KW - natural piezoelectric material KW - sugar KW - PVDF KW - organic piezoelectric nanogenerator KW - high performance and durability KW - self-powered electronics Y1 - 2018 U6 - https://doi.org/10.1021/acsami.8b15320 SN - 1944-8244 SN - 1944-8252 VL - 10 SP - 44018 EP - 44032 ER - TY - GEN A1 - Kot, Małgorzata A1 - Kegelmann, Lukas A1 - Das, Chittaranjan A1 - Kus, Peter A1 - Tsud, Nataliya A1 - Matolínová, Iva A1 - Albrecht, Steve A1 - Matolin, Vladimir A1 - Schmeißer, Dieter T1 - Room temperature atomic layer deposited Al₂O₃ improves perovskite solar cells efficiency over time T2 - ChemSusChem N2 - Electrical characterisation of perovskite solar cells consisting of room-temperature atomic-layer-deposited aluminium oxide (RT-ALD-Al₂O₃) film on top of a methyl ammonium lead triiodide (CH₃NH₃PbI₃) absorber showed excellent stability of the power conversion efficiency (PCE) over along time. Under the same environmental conditions (for 355 d), the average PCE of solar cells without the ALD layer decreased from 13.6 to 9.6 %, whereas that of solar cells containing 9 ALD cycles of depositing RT-ALD-Al₂O₃on top of CH₃NH₃PbI₃ increased from 9.4 to 10.8 %. Spectromicroscopic investigations of the ALD/perovskite interface revealed that the maximum PCE with the ALD layer is obtained when the so-called perovskite cleaning process induced by ALD precursors is complete. The PCE enhancement over time is probably related to a self-healing process induced by the RT-ALD-Al₂O₃ film. This work may provide a new direction for further improving the long-term stability and performance of perovskite solar cells. KW - Perovskite Solar Cells (PSCs) KW - Atomic layer deposition (ALD) KW - long time stabilty KW - X-Ray photoelectron spectroscopy (XPS) KW - Field-emission scanning electron microscopy (FESEM) Y1 - 2018 U6 - https://doi.org/10.1002/cssc.201801434 SN - 1864-5631 SN - 1864-564X VL - 11 IS - 20 SP - 3640 EP - 3648 ER - TY - GEN A1 - Schmeißer, Dieter A1 - Henkel, Karsten A1 - Janowitz, Christoph T1 - Ionicity of ZnO - a key system for transparent conductive oxides T2 - epl : a letters journal exploring the frontiers of physics N2 - The electronic structure of ZnO is dominated by coexisting electron and ionic states/bonds caused by charge polarization and self-trapping phenomena of the valence charges. Their interplay manifests itself in intrinsic electronic defects which have different degree of spatial localization and electronic correlation. The relative abundance of intrinsic defects can be determined by the ionicity factor fi and its value can be derived from three independent experimental procedures in a consistent way. This approach also explains the complex satellite features in the XPS and XAS data. Ionicity and satellite formation are two experimental findings which can be explained consistently in the same context of mixed-atomic valence states and intrinsic electronic defects. KW - Ionicity KW - zinc oxide (ZnO) KW - resonant photoelectron spectroscopy KW - defect states KW - transparent conductive oxide (TCO) Y1 - 2018 U6 - https://doi.org/10.1209/0295-5075/123/27003 SN - 1286-4854 SN - 0295-5075 VL - 123 IS - 2 SP - 27003-p1 EP - 27003-p7 ER - TY - CHAP A1 - Henkel, Karsten A1 - Haeberle, Jörg A1 - Müller, Klaus A1 - Janowitz, Christoph A1 - Schmeißer, Dieter ED - Fornari, Robert T1 - Preparation, properties and electronic structure of SnO₂ T2 - Single Crystals of Electronic Materials N2 - This chapter reports about tin oxide (SnO₂), a material which belongs to the transparent conducting oxide family and is best characterized by its high conductivity, high carrier mobility, and the ability to form p-type conductivity. We correlate these properties in terms of localized intrinsic electronic defect states which are resolved by resonant photoelectron spectroscopy measurements. We describe SnO₂ in terms of an inhomogeneous, mixed-ionic-covalent semiconductor in which these intrinsic electronic defects state are stabilized. KW - electronic structure KW - tin oxide (SnO₂) KW - resonant photoelectron spectroscopy KW - intrinsic defect states Y1 - 2018 SN - 978-0-08-102096-8 SN - 978-0-08-102097-5 SP - 547 EP - 572 PB - Elsevier, Woodhead Publishing CY - Duxford ER - TY - GEN A1 - Henkel, Karsten A1 - Kot, Małgorzata A1 - Schmeißer, Dieter T1 - Localized defect states and charge trapping in atomic layer deposited-Al₂O₃ films T2 - Journal of Vacuum Science and Technology, A : Vacuum, Surfaces, and Films N2 - In this study, the authors compared different Al₂O₃ films grown by atomic layer deposition (ALD) with the same aluminum precursor but on different substrates. The authors employed different process parameters such as thermal-ALD and plasma-enhanced-ALD using different substrate temperatures ranging from 280 °C down to room temperature. They characterized these films by resonant photoelectron spectroscopy and by electrical measurements. They established that generally the ALD-Al₂O₃ films show characteristic features of bulk Al₂O₃. For all films investigated, the authors found intrinsic defect states within the electronic band gap and identified excitonic, polaronic, and charge-transfer defect states. The authors gave an atomistic model to explain these intrinsic defects and found that their relative abundance is subject of the choice of ALD parameters and of the substrate used. They were able to relate the spectroscopic assigned in-gap defect states with the electronic charges as determined in our electrical measurements. KW - defect states KW - resonant photoelectron spectroscopy (resPES) KW - Al₂O₃ KW - atomic layer deposition (ALD) KW - excitons KW - polarons Y1 - 2017 U6 - https://doi.org/10.1116/1.4971991 SN - 0734-2101 SN - 1520-8559 VL - 35 IS - 1 SP - 01B125-1 EP - 01B125-18 ER - TY - GEN A1 - Henkel, Karsten A1 - Das, Chittaranjan A1 - Kot, Małgorzata A1 - Schmeißer, Dieter A1 - Naumann, Franziska A1 - Kärkkänen, Irina A1 - Gargouri, Hassan T1 - In-gap states in titanium dioxide and oxynitride atomic layer deposited films T2 - Journal of Vacuum Science and Technology: A N2 - Valence band (VB) spectra of titanium dioxide (TiO2) and oxynitride (TiOxNy) films prepared by different atomic layer deposition (ALD) processes are compared and related to electrical characterization [current–voltage (JV) and capacitance–voltage (CV)] results. By increasing the nitrogen amount in the TiO2 film, band-gap narrowing is observed. The band-gap decrease is related to the contribution of the nitrogen density of states, which induces defects within the band-gap and thus reduces its optical band-gap. In-gap states are found in the VB spectra at 1 eV below the Fermi energy in all investigated ALD samples, i.e., in TiO2 as well as in TiOxNy films. An exponential correlation between leakage current density and in-gap state intensity is derived by the combination of JV measurements and VB spectra, whereas the in-gap states seem to have no influence on hysteresis and fixed oxide charges found in the CV data. It is argued that the in-gap states in TiO2 and TiOxNy have an excitonic or polaronic origin. Both, band-gap narrowing and in-gap state intensity can be tuned by the ALD process selection and the variation of its parameters. KW - Titanium dioxide (TiO2) KW - Titanium oxynitrdie (TiON) KW - valence band spectra KW - in-gap states KW - band-gap narrowing KW - electrical characterization Y1 - 2017 U6 - https://doi.org/10.1116/1.4972247 SN - 0734-2101 SN - 1520-8559 VL - 35 IS - 1 SP - 01B135-1 EP - 01B135-8 ER - TY - GEN A1 - Menezes, Prashanth W. A1 - Indra, Arindam A1 - Das, Chittaranjan A1 - Walter, Carsten A1 - Göbel, Caren A1 - Gutkin, Vitaly A1 - Schmeißer, Dieter A1 - Driess, Matthias T1 - Uncovering the Nature of Active Species of Nickel Phosphide Catalysts in High-Performance Electrochemical Overall Water Splitting T2 - ACS Catalysis N2 - A systematic structural elucidation of the near-surface active species of the two remarkably active nickel phosphides Ni12P5 and Ni2P on the basis of extensive analytical, microscopic, and spectroscopic investigations is reported. The latter can serve as complementary efficient electrocatalysts in the hydrogen (HER) versus oxygen evolution reaction (OER) in alkaline media. In the OER Ni12P5 shows enhanced performance over Ni2P due to the higher concentration of nickel in this phase, which enables the formation of an amorphous NiOOH/Ni(OH)2 shell on a modified multiphase with a disordered phosphide/phosphite core. The situation is completely reversed in the HER, where Ni2P displayed a significant improvement in electrocatalytic activity over Ni12P5 owing to a larger concentration of phosphide/phosphate species in the shell. Moreover, the efficiently combined use of the two nickel phosphide phases deposited on nickel foam in overall electrocatalytic water splitting is demonstrated by a strikingly low cell voltage and high stability with pronounced current density, and these catalysts could be an apt choice for applications in commercial alkaline water electrolysis. KW - overall water splitting KW - electrocatalysis KW - nickel phosphide KW - structural rearrangement KW - surface structure Y1 - 2017 U6 - https://doi.org/10.1021/acscatal.6b02666 SN - 2155-5435 VL - 7 IS - 1 SP - 103 EP - 109 ER - TY - GEN A1 - Müller, Klaus A1 - Rachow, Fabian A1 - Israel, Johannes A1 - Charlafti, Evgenia A1 - Schwiertz, Carola A1 - Schmeißer, Dieter T1 - Direct Methanation of Flue Gas at a Lignite Power Plant T2 - International Journal of Environmental Science N2 - The combustion of fossil fuels results in CO2 emission, which is one of the primary causes of global warming. An important approach for solving this problem is the fixation, the chemical utilization and the recycling of CO2. Therefore, we investigate the catalytic conversion of CO2 with H2 into methane (CH4) with an upscaled test station at a brown coal power plant. In a completely new strategy, we realize the direct conversion of the CO2 content of the flue gas, without a cleaning process like amine scrubbing or optimized combustion like oxyfuel. Our experiments are performed in matters of catalytic performance, heat production and stability of the catalytic Sabatier process, as a function of the gas flow rate. The catalytic performance is investigated with a simulated composition of flue gas and under real conditions directly at the power plant. The CH4 production by the Sabatier process is realized with a maximum input flow rate of near 50Nm3/h, with 30Nm3/h flue gas and 20Nm3/h hydrogen. For these values, the necessary power scale for hydrogen generation by electrolysis is around 100kW. With synthetic and real flue gas, a conversion up to 99% (for hydrogen surplus) with 100% selectivity is stabilized. The reaction operates in thermal steady state equilibrium without any external energy supply. In consequence, the process of CO2 recycling could be integrated directly as a post combustion process of conventional power plants, without an expensive capturing step, for example. KW - CO2 recycling KW - Power to Gas (PtG) KW - Synthetic Natural Gas (SNG) KW - Sabatier-Reaction KW - Flue Gas Y1 - 2017 UR - http://www.iaras.org/iaras/home/caijes/direct-methanation-of-flue-gas-at-a-lignite-power-plant SN - 2367-8941 IS - 2 SP - 425 EP - 437 ER - TY - GEN A1 - Indra, Arindam A1 - Menezes, Prashanth W. A1 - Das, Chittaranjan A1 - Göbel, Caren A1 - Tallarida, Massimo A1 - Schmeißer, Dieter A1 - Driess, Matthias T1 - A facile corrosion approach to the synthesis of highly active CoOxwater oxidation catalysts T2 - Journal of Materials Chemistry A N2 - Ultra-small rock salt cobalt monoxide (CoO) nanoparticles were synthesized and subjected to partial oxidation (‘corrosion’) with ceric ammonium nitrate (CAN) to form mixed-valence CoOx(1 < x< 2) water oxidation catalysts. Spectroscopic, microscopic and analytical methods evidenced a structural reformation of cubic CoO to active CoOx with a spinel structure. The superior water oxidation activity of CoOx has been established in electrochemical water oxidation under alkaline conditions. Electrochemical water oxidation with CoOx was recorded at a considerably low overpotential of merely 325 mV at a current density of 10 mA cm-2 in comparison to 370 mV for CoO. Transformation of both octahedral CoII and CoIII sites into amorphous Co(OH)2–CoOOH is the key to high electrochemical activity while the presence of a higher amount of octahedral CoIII sites in CoOx is imperative for an efficient oxygen evolution process. KW - water splitting KW - water oxidation KW - cobalt oxide catalyst KW - transmission electron microscopy (TEM) KW - X-ray photoelectron spectroscopy (XPS) KW - X-ray absorption spectroscopy (XAS) KW - Cyclic voltammetry (CV) Y1 - 2017 U6 - https://doi.org/10.1039/c6ta10650a SN - 2050-7488 SN - 2050-7496 IS - 5 SP - 5171 EP - 5177 ER - TY - GEN A1 - Kot, Małgorzata A1 - Henkel, Karsten A1 - Das, Chittaranjan A1 - Brizzi, Simone A1 - Kärkkänen, Irina A1 - Schneidewind, Jessica A1 - Naumann, Franziska A1 - Gargouri, Hassan A1 - Schmeißer, Dieter T1 - Analysis of titanium species in titanium oxynitride films prepared by plasma enhanced atomic layer deposition T2 - Surface and Coatings Technology N2 - A comparative study of thin titanium oxynitride (TiOxNy) films prepared by plasma enhanced atomic layer deposition using tetrakis(dimethylamino)titanium (TDMAT) and N2 plasma as well as titanium(IV)isopropoxide and NH3 plasma is reported. The comparison is based on the combination of Ti2p core level and valence band spectroscopy and current-voltage measurements. The TDMAT/N2 process delivers generally higher fractions of TiN and TiON within the Ti2p spectra of the films and stronger photoemissions within the bandgap as resolved in detail by high energy resolution synchrotron-based spectroscopy. In particular, it is shown that higher TiN contributions and in-gap emission intensities correlate strongly with increased leakage currents within the films and might be modified by the process parameters and precursor selection. KW - Titanium oxynitride KW - Plasma enhanced atomic layer deposition (PEALD) KW - ALD process parameters KW - Ti-N contributions KW - In-gap defect states KW - Leakage current Y1 - 2017 U6 - https://doi.org/10.1016/j.surfcoat.2016.11.094 SN - 0257-8972 SN - 1879-3347 VL - 324 SP - 586 EP - 593 ER - TY - GEN A1 - Das, Chittaranjan A1 - Kot, Małgorzata A1 - Rouissi, Zied A1 - Kędzierski, Kamil A1 - Henkel, Karsten A1 - Schmeißer, Dieter T1 - Selective Deposition of an ultrathin Pt Layer on a Au-Nanoisland-Modified Si Photocathode for Hydrogen Generation T2 - ACS Omega N2 - Platinum, being the most efficient and stable catalyst, is used in photoelectrochemical (PEC) devices. However, a minimal amount of Pt with maximum catalytic activity is required to be used to minimize the cost of production. In this work, we use an environmentally friendly, ost-effective, and less Pt-consuming method to prepare PEC devices for the hydrogen evolution reaction (HER). The Pt monolayer catalyst is selectively deposited on a Au-nanoisland-supported boron-doped p-type Si (100) photocathode. The PEC device based on the Si photocathode with an ultralow loading of the Pt catalyst exhibits a comparable performance for the HER to that of devices with a thick Pt layer. In addition, we demonstrate that by using a thin TiO2 layer deposited by atomic layer deposition photo-oxidation of the Si photocathode can be blocked resulting in a stable PEC performance. KW - water splitting KW - hydrogen evolution reaction (HER) KW - Si photocathode KW - gold nanoislands KW - nanostructured platinum Y1 - 2017 U6 - https://doi.org/10.1021/acsomega.6b00374 SN - 2470-1343 VL - 2 IS - 4 SP - 1360 EP - 1366 ER - TY - GEN A1 - Kot, Małgorzata A1 - Das, Chittaranjan A1 - Henkel, Karsten A1 - Wojciechowski, Konrad A1 - Snaith, Henry J. A1 - Schmeißer, Dieter T1 - Room temperature atomic layer deposited Al₂O₃ on CH₃NH₃PbI₃ characterized by synchrotron-based X-ray photoelectron spectroscopy T2 - Nuclear Instruments and Methods in Physics Research B N2 - An ultrathin Al₂O₃ film deposited on methylammonium lead triiodide (CH₃NH₃PbI₃) perovskite has the capability to suppress the carrier recombination process and improve the perovskite solar cells efficiency and stability. However, annealing at temperatures higher than 85°C degrades the CH₃NH₃PbI₃ perovskite film. The X-ray photoelectron spectroscopy study performed in this work indicates that it is possible to grow Al₂O₃ by atomic layer deposition on the perovskite at room temperature, however, besides pure Al₂O₃ some OH groups are found and the creation of lead and iodine oxides at the Al₂O₃/CH₃NH₃PbI₃ interface takes place. KW - Synchrotron-based X-ray photoelectron spectroscopy KW - Perovskite solar cells KW - Atomic layer deposition KW - Al₂O₃ Y1 - 2017 U6 - https://doi.org/10.1016/j.nimb.2017.01.082 SN - 0168-583X SN - 1872-9584 VL - 411 SP - 49 EP - 52 ER - TY - GEN A1 - Cibrev, Dejan A1 - Tallarida, Massimo A1 - Das, Chittaranjan A1 - Lana-Villarreal, Teresa A1 - Schmeißer, Dieter A1 - Gómez, Roberto T1 - New insights into water photooxidation on reductively pretreated hematite photoanodes T2 - Physical Chemistry Chemical Physics N2 - It has been recently demonstrated that the photoactivity toward oxygen evolution of a number of n-type metal oxides can be substantially improved by a reductive electrochemical pretreatment. Such an enhancement has been primarily linked to the formation of low valent metal species that increase electrode conductivity. In this work, we report new insights into the electrochemical doping using highly ordered (110)-oriented hematite nanorods directly grown on FTO. The reductive pretreatment consists in applying negative potentials for a controlled period of time. Such a pretreatment was optimized in both potentiostatic and potentiodynamic regimes. We show that the optimized pretreatment enhances electrode conductivity due to an increase in charge carrier density. However, it additionally triggers changes in the morphologic, catalytic and electronic properties that facilitate the separation and collection of the photogenerated charge carriers causing an up to 8-fold enhancement in the photocurrent for water oxidation. The reductive pretreatment can be considered as a highly controllable electrochemical n-type doping with the amount of generated Fe2+/polaron species and the change in film morphology as the main factors determining the final efficiency for water photooxidation of the resulting electrodes. KW - hematite KW - photoanode KW - water oxidation KW - water splitting Y1 - 2017 U6 - https://doi.org/10.1039/C7CP03958A SN - 1463-9076 SN - 1463-9084 VL - 19 IS - 32 SP - 21807 EP - 21817 ER - TY - GEN A1 - Biswas, Anirban A1 - Henkel, Karsten A1 - Schmeißer, Dieter A1 - Mandal, Dipankar T1 - Comparison of the thermal stability of the α, β and γ phases in poly(vinylidene fluoride) based on in situ thermal Fourier transform infrared spectroscopy T2 - Phase Transitions N2 - The electroactive β phase of poly(vinylidenefluoride) (PVDF) is induced due to the aging time of PVDF solutions. The feasibility of the combination of the three crystalline polymorphs (α, β and γ) is demonstrated where their relative proportion within the PVDF film can be tailored by the simple monitoring of the preparation conditions. To identify all these phases, Fourier transform infrared (FT-IR) spectroscopy is carried out and it is spotlighted that the vibrational bands at 510 and 841 cm-1 are not sufficient to state the formation of the β phase. The main aim of this work is devoted to develop a better understanding on the thermal stability of these several phases of PVDF, which has a longstanding ambiguity persisting in this area. It has been found that the in situ thermal FT-IR spectroscopy is one of the best alternatives to understand this important issue. It is ascertained that the β phase is the least thermally stable phase among α, β and γ phases, whereas the γ phase is the most thermally stable phase. KW - PVDF KW - thermal stability KW - β-phase KW - infrared spectroscopy KW - in situ thermal FT-IR study Y1 - 2017 U6 - https://doi.org/10.1080/01411594.2017.1337902 SN - 0141-1594 SN - 1029-0338 VL - 90 IS - 12 SP - 1205 EP - 1213 ER - TY - GEN A1 - Indra, Arindam A1 - Menezes, Prashanth W. A1 - Das, Chittaranjan A1 - Schmeißer, Dieter A1 - Driess, Matthias T1 - Alkaline electrochemical water oxidation with multi-shelled cobalt manganese oxide hollow spheres T2 - Chemical Communications N2 - Multi-shelled hollow spheres of cobalt manganese oxides (CMOs) deposited on Ni foam exhibited superior alkaline electrochemical water oxidation activity and surpassed those of bulk CMO and commercial noble metal-based catalysts. A higher amount of cobalt in the spinel structure resulted in the transformation of the tetragonal to the cubic phase with a decrease in the overpotential of oxygen evolution. KW - Water oxidation KW - Cobalt manganese oxides (CMOs) KW - Multi-shelled hollow spheres KW - Near-edge X-ray absorption fine structure (NEXAFS) KW - Cyclic voltammetry KW - Scanning electron microscopy Y1 - 2017 U6 - https://doi.org/10.1039/C7CC03566G SN - 1359-7345 SN - 1364-548X VL - 53 IS - 62 SP - 8641 EP - 8644 ER - TY - GEN A1 - Alberton Corrêa, Silma A1 - Brizzi, Simone A1 - Schmeißer, Dieter T1 - Spectroscopic investigation of the electronic structure of thin atomic layer deposition HfO2 films T2 - Journal of Vacuum Science & Technology A N2 - The electronic structure of HfO2 thin films is investigated employing resonant photoelectron spectroscopy (resPES). The detailed analysis of the O1s resonance profile enables the determination of the partial density of states for the valence and the conduction bands as well as the electronic band gap to be 6.2 eV. The position of the charge neutrality level is evaluated. Thereby, it is demonstrated that the resPES data are able to combine information both for the valence as well as for the conduction band states. In addition, evidences for intrinsic in-gap states attributed to polaronic and charge transfer states are given. Electronic charges within the atomic layer deposition-HfO2films are identified, pointing out that the amount of charges is essential to determine the accurate position of the surface potentials. KW - resonant photoelectron spectroscopy KW - hafnium oxide KW - atomic layer deposition KW - partial density of states KW - electronic band gap Y1 - 2016 U6 - https://doi.org/10.1116/1.4935338 SN - 0734-2101 SN - 1520-8559 VL - 34 IS - 1 SP - 01A117-1 EP - 01A117-8 ER - TY - GEN A1 - Pitthan, E. A1 - dos Reis, R. A1 - Alberton Corrêa, Silma A1 - Schmeißer, Dieter A1 - Boudinov, H. I. A1 - Stedile, F. C. T1 - Influence of CO annealing in metal-oxide-semiconductor capacitors with SiO2 films thermally grown on Si and on SiC T2 - Journal of Applied Physics N2 - Understanding the influence of SiC reaction with CO, a by-product of SiC thermal oxidation, is a key point to elucidate the origin of electrical defects in SiC metal-oxide-semiconductor (MOS) devices. In this work, the effects on electrical, structural, and chemical properties of SiO2/Si and SiO2/SiC structures submitted to CO annealing were investigated. It was observed that long annealing times resulted in the incorporation of carbon from CO in the Si substrate, followed by deterioration of the SiO2/Si interface, and its crystallization as SiC. Besides, this incorporated carbon remained in the Si surface (previous SiO2/Si region) after removal of the silicon dioxide film by HF etching. In the SiC case, an even more defective surface region was observed due to the CO interaction. All MOS capacitors formed using both semiconductor materials presented higher leakage current and generation of positive effective charge after CO annealings. Such results suggest that the negative fixed charge, typically observed in SiO2/SiC structures, is not originated from the interaction of the CO by-product, formed during SiC oxidation, with the SiO2/SiC interfacial region. KW - metal-oxide-semiconductor KW - silicon KW - silicon carbide KW - CO annealing Y1 - 2016 U6 - https://doi.org/10.1063/1.4939836 SN - 0021-8979 SN - 1089-7550 IS - 119 SP - 025307-1 EP - 025307-6 ER - TY - GEN A1 - Sowińska, Małgorzata A1 - Henkel, Karsten A1 - Schmeißer, Dieter A1 - Kärkkänen, Irina A1 - Schneidewind, Jessica A1 - Naumann, Franziska A1 - Gruska, Bernd A1 - Gargouri, Hassan T1 - Plasma-enhanced atomic layer deposition of titanium oxynitrides films: A comparative spectroscopic and electrical study T2 - Journal of Vacuum Science and Technology A N2 - The process parameters’ impact of the plasma-enhanced atomic layer deposition (PE-ALD) method on the oxygen to nitrogen (O/N) ratio in titanium oxynitride (TiOxNy) films was studied. Titanium(IV)isopropoxide in combination with NH3 plasma and tetrakis(dimethylamino) titanium by applying N2 plasma processes were investigated. Samples were characterized by the in situ spectroscopic ellipsometry, x-ray photoelectron spectroscopy, and electrical characterization (current–voltage: I-V and capacitance–voltage: C-V) methods. The O/N ratio in the TiOxNy films is found to be very sensitive for their electric properties such as conductivity, dielectric breakdown, and permittivity. Our results indicate that these PE-ALD film properties can be tuned, via the O/N ratio, by the selection of the process parameters and precursor/coreactant combination. KW - plasma enhanced atomic layer deposition KW - titanium oxynitride KW - X-ray photoelectron spectroscopy KW - ellipsometry KW - current-voltage KW - capacitance-voltage Y1 - 2016 U6 - https://doi.org/10.1116/1.4936227 SN - 0734-2101 SN - 1520-8559 IS - 34 SP - 01A127-1 EP - 01A127-9 ER - TY - GEN A1 - Garain, Samiran A1 - Barman, Koushik A1 - Sinha, Tridib Kumar A1 - Jasimuddin, Sk A1 - Haeberle, Jörg A1 - Henkel, Karsten A1 - Schmeißer, Dieter A1 - Mandal, Dipankar T1 - Cerium(III) Complex Modified Gold Electrode: An Efficient Electrocatalyst for the Oxygen Evolution Reaction T2 - ACS Applied Materials and Interfaces N2 - Exploring efficient and inexpensive electrocatalysts for the oxidation of water is of great importance for various electrochemical energy storage and conversion technologies. In the present study, a new water-soluble [Ce III(DMF) (HSO4)3] complex was synthesized and characterized by UV−vis, photoluminescence, and high-resolution X-ray photoelectron spectroscopy techniques. Owing to classic 5d →4f transitions, an intense photoluminescence in the UV region was observed from the water-soluble [CeIII(DMF)(HSO4)3] complex. A stacking electrode was designed where self-assembled L-cysteine monolayer modified gold was immobilized with the synthesized cerium complex and was characterized by scanning electron microscopy, electrochemical impedance spectroscopy, and cyclic voltam-metry. The resulting electrode, i.e., [CeIII(DMF)(HSO4)3]−L-cysteine-Au stacks shows high electrocatalytic water oxidation behavior at an overpotential of η ≈0.34 V under neutral pH conditions. We also demonstrated a way where the overpotential is possible to decrease upon irradiation of UV light. KW - water oxidation KW - electrocatalyst KW - photoelectrocatalyst KW - photoluminescence KW - Ce(III)-complex KW - L-cysteine KW - gold electrode Y1 - 2016 U6 - https://doi.org/10.1021/acsami.6b05236 SN - 1944-8244 SN - 1944-8252 VL - 8 IS - 33 SP - 21294 EP - 21301 ER - TY - GEN A1 - Sowinska, Małgorzata A1 - Brizzi, Simone A1 - Das, Chittaranjan A1 - Kärkkänen, Irina A1 - Schneidewind, Jessica A1 - Naumann, Franziska A1 - Gargouri, Hassan A1 - Henkel, Karsten A1 - Schmeißer, Dieter T1 - Analysis of nitrogen species in titanium oxynitride ALD films T2 - Applied Surface Science N2 - Titanium oxynitride films are prepared by plasma enhanced atomic layer deposition method using two different precursors and nitrogen sources. Synchrotron radiation-based X-ray photoelectron spectroscopy and X-ray absorption spectroscopy are used to characterize the nitrogen species incorporated within these films depending on the deposition parameters. It is found that nitrogen atoms in these films are differently bonded. In particular, it can be distinguished between Ti-ON and Ti-N bonding configurations and molecular nitrogen species caused by precursor fragments. KW - titanium oxynitride KW - X-ray photoelectron spectroscopy KW - X-ray absorption spectroscopy KW - ALD process parameters Y1 - 2016 U6 - https://doi.org/10.1016/j.apsusc.2016.02.096 SN - 0169-4332 SN - 1873-5584 VL - 381 SP - 42 EP - 47 ER - TY - GEN A1 - Schmeißer, Dieter A1 - Haeberle, Jörg T1 - Intrinsic localized gap states in IGZO and its parent single crystalline TCOs T2 - Thin Solid Films N2 - We report on the X-ray absorption data for Indium–Gallium–Zink–Oxide thin films, amorphous ZnO films, amorphous SnOx films, and single crystalline In2O3, Ga2O3, ZnO, and SnO2 data. These absorption data probe the empty conduction band states explicitly. Also they allow for an elemental assignment using resonant excitation to derive the contributions of each metal ion. We find that the lowest states appear right at the Fermi energy and result from configuration interaction induced charge transfer states which we consider as intrinsic gap states. KW - Transparent conducting oxide KW - X-ray photoelectron spectroscopy KW - Resonant photoemission spectroscopy KW - X-ray absorption spectroscopy KW - Electronic band structure KW - Intrinsic localized gap states Y1 - 2016 U6 - https://doi.org/10.1016/j.tsf.2016.02.010 SN - 0040-6090 SN - 1879-2731 IS - 603 SP - 206 EP - 211 ER - TY - GEN A1 - Kramm, Ulrike Ingrid A1 - Zana, Alessandro A1 - Vosch, Tom A1 - Fiechter, Sebastian A1 - Arenz, Matthias A1 - Schmeißer, Dieter T1 - On the structural composition and stability of Fe–N–C catalysts prepared by an intermediate acid leaching T2 - Journal of Solid State Electrochemistry N2 - The development of highly active and stable non-noble metal catalysts (NNMC) for the oxygen reduction reaction (ORR) in proton exchange membrane fuel cells (PEM-FC) becomes of importance in order to enable cost reduction. In this work, we discuss the structural composition as derived from Fe-57Mößbauer spectroscopy and X-ray diffraction, catalytic performance determined by a rotating (ring)disk electrode (RRDE) technique and stability evaluation of our Fe–N–C catalysts prepared by an intermediate acid leaching (IAL). The advantage of this IAL is given by a high density of active sites within the catalyst, as even without sulphur addition, an iron carbide formation and related disintegration of active sites are inhibited. In addition, our accelerated stress tests illustrate better stability of the sulphur-free IAL catalyst in comparison to the sulphur-added one. KW - Non-noblemetal catalysts (NNMC) KW - Fe–N–C KW - oxygen reduction reaction (ORR) KW - PEM fuel cell (PEM-FC) KW - Accelerated stress tests (ASTs) KW - Mößbauer spectroscopy Y1 - 2016 U6 - https://doi.org/10.1007/s10008-015-3060-z SN - 1432-8488 SN - 1433-0768 N1 - 1. ISSN: P 2. ISSN: E VL - 20 IS - 4 SP - 969 EP - 981 ER - TY - CHAP A1 - Sowinska, Małgorzata A1 - Das, Chittaranjan A1 - Wojciechowski, Konrad A1 - Snaith, Henry J. A1 - Schmeißer, Dieter T1 - XPS study of the ALD growth of Al₂O₃ on the CH₃NH₃PbI₃ T2 - Verhandlungen der Deutschen Physikalischen Gesellschaft N2 - Organic-inorganic lead halide perovskites have emerged as very attractive absorber materials for the fabrication of low cost and high efficiency solar cells, but a delicate nature of these films is one of the main challenges for a successful commercialization. Typically, when exposed to air or moisture, perovskite films degrade within a couple of hours or days. Moreover, the methylammonium lead triiodide (CH₃NH₃PbI₃) perovskite cannot sustain a prolonged annealing at temperatures around 85∘C. In this work, we are investigating stability (upon air and thermal exposure) of a CH₃NH₃PbI₃ perovskite film coated with a thin layer of Al₂O₃ deposited by atomic layer deposition (ALD). In particular, the chemical and electronic changes occurred at the Al₂O₃/CH₃NH₃PbI₃ interface during the first 50 ALD cycles were monitored ex-situ by high-resolution and surface-sensitive synchrotron-based X-ray photoelectron spectroscopy (SR-XPS). The advantage of the ALD as a deposition method is that it can produce extremely dense layers with a very precise thickness control at room temperature. Detailed SR-XPS data analysis and a stability test of the perovskite film with alumina will be presented. KW - atomic layer deposition KW - perovskite solar cells KW - Al₂O₃ KW - X-Ray photoelectron spectroscopy KW - synchrotron Y1 - 2016 UR - http://www.dpg-verhandlungen.de/year/2016/conference/regensburg/part/cpp/session/31/contribution/6?lang=en SP - S. 206 PB - Deutsche Physikalische Gesellschaft CY - Bad Honnef ER - TY - CHAP A1 - Das, Chittaranjan A1 - Tallarida, Massimo A1 - Schmeißer, Dieter T1 - TiO2 laminated Silicon microstructures based stable photocathode for water splitting T2 - Verhandlungen der Deutschen Physikalischen Gesellschaft N2 - The photoelectrochemical (PEC) water splitting is one of the most efficient ways to obtain hydrogen from water using solar power which can be used as carbon free fuel. The PEC device can bedesigned using semiconducting material that will convert solar radiation to H2. Silicon can be one of the best choices for PEC due to its success in solar cells technology. There are certain issues with Si such as stability in electrochemical medium [1] and higher surface reflectance (25%) which limits the Si as an ideal candidate for PEC technique [2]. In the present work we addressed these issues by surface structuring and laminating the surface with metal oxide. The microstructuring of Si was done by electrochemical method. The Si microstructure photocathode was stabilized by thin layer of ALD grown TiO2 film. The microstructuring and lamination of Si photocathode by ALD layer of TiO2 decreased the reflectance ofthe surface and shift the onset potential towards anodic direction by 350 mV with a prolonged stability over 60 hours[3]. [1] C. Levy-Clement, J. Electrochem. Soc 1991, 12, 69 [2] J. Oh, et al. Energy Environ. Sci., 2011, 4, 1690 [3] C. Das, et al. Nanoscale 2015,7, 7726 KW - water splitting KW - TiO2 KW - atomic layer deposition (ALD) KW - Si photoelectrodes Y1 - 2016 UR - http://www.dpg-verhandlungen.de/year/2016/conference/regensburg/part/ds/session/48/contribution/4?lang=en SP - S. 213 PB - Deutsche Physikalische Gesellschaft CY - Bad Honnef ER - TY - GEN A1 - Haeberle, Jörg A1 - Machulik, Stephan A1 - Janowitz, Christoph A1 - Manzke, Recardo A1 - Gaspar, Diana A1 - Barquinha, Pedro A1 - Schmeißer, Dieter T1 - Gap states in the electronic structure of SnO2 single crystals and amorphous SnOxthin films T2 - Journal of Applied Physics N2 - The electronic structure of a SnO2 single crystal is determined by employing resonant photoelectron spectroscopy. We determine the core level, valence band, and X-ray absorption (XAS) data and compare these with those of amorphous SnOx thin films. We find similar properties concerning the data of the core levels, the valence band features, and the absorption data at the O1s edge. We find strong signals arising from intrinsic in-gap states and discuss their origin in terms of polaronic and charge-transfer defects. We deduce from the XAS data recorded at the Sn3d edge that the Sn4d10 ground state has contributions of 4d9 and 4d8 states due to configuration interaction. We identify localized electronic states depending on the strength of the 4d-5s5p interaction and of the O2p-to-Sn4d charge-transfer processes, both appear separated from the extended band-like states of the conduction band. For the amorphous SnOx thin films, significant differences are found only in the absorption data at the Sn3d-edge due to a stronger localization of the in-gap states. KW - SnO2 KW - electronic structure KW - gap states KW - resonant photoelectron spectroscopy (resPES) Y1 - 2016 U6 - https://doi.org/10.1063/1.4962313 SN - 0021-8979 SN - 1089-7550 VL - 120 IS - 10 SP - 105101-1 EP - 105101-13 ER - TY - GEN A1 - Sowinska, Małgorzata A1 - Das, Chittaranjan A1 - Wojciechowski, Konrad A1 - Rouissi, Zied A1 - Snaith, Henry J. A1 - Schmeißer, Dieter T1 - Atomic layer deposition of Al2O3 on CH3NH3PbI3 for enhancement of perovskite solar cells stability T2 - Synchrotron Radiation in Natural Science : Bulletin of the Polish Synchrotron Radiation Society KW - atomic layer deposition KW - perovskite soloar cells KW - X-ray photoelectron spectroscopy (XPS) KW - Atomic foce microscopy (AFM) Y1 - 2016 SN - 1644-7190 VL - 15 IS - 1-2 SP - S. 33 ER - TY - CHAP A1 - Rouissi, Zied A1 - Tallarida, Massimo A1 - Schmeißer, Dieter T1 - HfO2 grow by ALD on Si(111)-H terminated stepped surface T2 - Verhandlungen der Deutschen Physikalischen Gesellschaft N2 - We studied by STM the growth of HfO2 on Si (111)-H stepped surface (miscut by 0.5∘). The steps are aligned in the [11-2] direction. In order to obtain well defined steps and terraces we prepare the sample by chemical etching in 40% Nh4F. In our in-situ study we investigate the ALD growth of HfO2 by TDMAH and H2O [1-2]. We follow for the first four ALD cycles the distribution of the nucleation sites. We also study the influence of the substrate temperature by comparing the growth within the ALD window at 300K and 580K. We observed that at RT the as-grown HfO2 forms stripes which are oriented normal to the step orientations. Further growth starts from the step edges and proceeds towards the terraces. Defects created by the etching processes act as nucleation sites for 3D islands. Based on our STM data we are able to correlate the structural changes on that inert and stepped Si(111)-H surface during ALD with experimental [3] and theoretical [4] results obtained for planar Si(100) surfaces. [1] M. Tallarida et al., Semicond. Sci. Technol. 27, 074010 (2012) [2] K. Kolanek et al., Thin Solid Films 518, 4688 (2010) [3] K. Kolanek et al., J. Vac. Sci. Technol. A 31, 01A104 (2013) [4]L. Riikka et al., J. Appl. Phys.96, 7686 (2004) KW - atomic layer deposition KW - stepped surfaces KW - scanning tunneling micrsocopy KW - HfO2 KW - Si(111) Y1 - 2016 UR - http://www.dpg-verhandlungen.de/year/2016/conference/regensburg/part/o/session/89/contribution/13?lang=en SP - S. 419 PB - Deutsche Physikalische Gesellschaft CY - Bad Honnef ER -