@misc{HoffmannMikaloYfantisetal., author = {Hoffmann, Patrick and Mikalo, Ricardo Pablo and Yfantis, Alexandros D. and Batchelor, David R. and Appel, G{\"u}nter and Schmeißer, Dieter}, title = {A Spectro-Microscopic Approach for Thin Film Analysis Grain Boundaries in mc-Si and Sn/SnO2 Nano Particles}, series = {Microchimica Acta}, volume = {136}, journal = {Microchimica Acta}, number = {3-4}, issn = {1436-5073}, pages = {109 -- 113}, language = {en} } @misc{MuellerPaloumpaHenkeletal., author = {M{\"u}ller, Klaus and Paloumpa, Ioanna and Henkel, Karsten and Schmeißer, Dieter}, title = {A polymer high-k dielectric insulator for organic field effect Transistors}, series = {Journal of Applied Physics}, volume = {98}, journal = {Journal of Applied Physics}, number = {5}, issn = {0021-8979}, pages = {S. 056104}, language = {en} } @article{SchmittZhuSchmeisseretal., author = {Schmitt, Andrew L. and Zhu, Lei and Schmeißer, Dieter and Himpsel, Franz J. and Jin, Song}, title = {Metallic Single-Crystal CoSi Nanowires via Chemical Vapor Deposition of Single-Source Precursor}, language = {en} } @article{SchmittBiermanSchmeisseretal., author = {Schmitt, Andrew L. and Bierman, Matthew J. and Schmeißer, Dieter and Himpsel, Franz J. and Jin, Song}, title = {Synthesis and Properties of Single-Crystal FeSi Nanowires}, language = {en} } @misc{SchmeisserHenkelMuelleretal., author = {Schmeißer, Dieter and Henkel, Karsten and M{\"u}ller, Klaus and Tallarida, Massimo}, title = {Interface Reactions in Ultrathin Functional Dielectric Films}, language = {en} } @misc{LazarevaKovalMuelleretal., author = {Lazareva, I. and Koval, Yuri and M{\"u}ller, P. and M{\"u}ller, Klaus and Henkel, Karsten and Schmeißer, Dieter}, title = {Interface screening and imprint in pol(vinylidene fluoride/trifluoroethylene) ferroelectric field effect transistors}, language = {en} } @incollection{MuellerBurkovMandaletal., author = {M{\"u}ller, Klaus and Burkov, Yevgen and Mandal, Dipankar and Henkel, Karsten and Paloumpa, Ioanna and Goryachko, Andriy and Schmeißer, Dieter}, title = {Microscopic and spectroscopic characterization of interfaces and dielectric layers for OFET devices}, series = {Organic Electronics : structural and Electronic Properties of OFETs}, booktitle = {Organic Electronics : structural and Electronic Properties of OFETs}, editor = {W{\"o}ll, Christof}, publisher = {Wiley-VCH}, address = {Weinheim}, isbn = {978-3-527-40810-8}, pages = {445 -- 468}, language = {en} } @misc{TallaridaKaravaevSchmeisser, author = {Tallarida, Massimo and Karavaev, Konstantin and Schmeißer, Dieter}, title = {HfO2/Si interface formation in atomic layer deposition films: an in situ investigation}, language = {en} } @article{HoffmannMikaloSchmeisser, author = {Hoffmann, Patrick and Mikalo, Ricardo Pablo and Schmeißer, Dieter}, title = {Si(001) surface oxidation by N2O}, abstract = {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.}, language = {en} } @article{SchmeisserHoffmann, author = {Schmeißer, Dieter and Hoffmann, Patrick}, title = {Characterisation of the PrOx/Si(001) Interface by Photoelectron Spectroscopy}, language = {en} } @misc{HenkelSohalTorcheetal., author = {Henkel, Karsten and Sohal, Rakesh and Torche, Mohamed and Paloumpa, Ioanna and M{\"u}ller, Klaus and Hoffmann, Patrick and Schmeißer, Dieter}, title = {Grenzfl{\"a}chenoptimierung f{\"u}r funktionale D{\"u}nnschichtsysteme: Oxide und Polymere}, series = {Forum der Forschung}, volume = {9}, journal = {Forum der Forschung}, number = {18}, issn = {0947-6989}, pages = {49 -- 56}, language = {de} } @misc{SchmeisserHimpselDenlingeretal., author = {Schmeißer, Dieter and Himpsel, Franz J. and Denlinger, Jonathan D. and Ederer, David L.}, title = {Resonante Photoemission an der Cu2p Kante von Cu und CuO}, series = {Forum der Forschung}, volume = {9}, journal = {Forum der Forschung}, number = {18}, issn = {0947-6989}, pages = {57 -- 62}, language = {de} } @article{MuellerBurkovSchmeisser, author = {M{\"u}ller, Klaus and Burkov, Yevgen and Schmeißer, Dieter}, title = {Photo-Emission-Electron-Microscopy for Characterization of an Operating Organic Electronic Device}, language = {en} } @article{Schmeisser, author = {Schmeißer, Dieter}, title = {The Consequences of anisotropic Diffusion and Noise: PEEM at the CO Oxidation Reaction on Stepped Ir(111) Surfaces}, language = {en} } @misc{MuellerHenkelMandaletal., author = {M{\"u}ller, Klaus and Henkel, Karsten and Mandal, Dipankar and Seime, Bernd and Paloumpa, Ioanna and Schmeißer, Dieter}, title = {Spin coated organic ferroelectric films for non volatile memories}, language = {en} } @misc{SeifarthSchubertGiussanietal., author = {Seifarth, Olaf and Schubert, Markus Andreas and Giussani, A. and Klenov, D. O. and Schmeißer, Dieter and Schroeder, Thomas}, title = {Single crystalline Pr2-xYxO3 (x=0-2)dielectrics on Si with tailored electronic and crystallographic structure}, volume = {108}, number = {10}, issn = {1089-7550}, pages = {103709}, language = {en} } @misc{MandalHenkelMuelleretal., author = {Mandal, Dipankar and Henkel, Karsten and M{\"u}ller, Klaus and Schmeißer, Dieter}, title = {Band gab determination of P(VDF-TrFE) copolymer film by electron energy loss spectroscopy}, language = {en} } @misc{KolanekTallaridaKaravaevetal., author = {Kolanek, Krzysztof and Tallarida, Massimo and Karavaev, Konstantin and Schmeißer, Dieter}, title = {In situ studies of the atomic layer deposition of thin HfO2 dielectrics by ultra high vacuum atomic force microscope}, language = {en} } @article{SchmeisserSeiboldReif, author = {Schmeißer, Dieter and Seibold, G{\"o}tz and Reif, J{\"u}rgen}, title = {Nano-scaled Dielectric Barriers (NanoDieB) for CMOS compatible Si-technologies}, series = {Forum der Forschung}, journal = {Forum der Forschung}, number = {19}, issn = {0947-6989}, pages = {131 -- 136}, language = {en} } @inproceedings{StarzykTallaridaSchmeisser, author = {Starzyk, Łukasz and Tallarida, Massimo and Schmeißer, Dieter}, title = {Band alignment of high-k/SiO2/Si stacks incorporating Zr and Al oxides prepared by atomic layer deposition}, language = {en} } @misc{KolanekTallaridaSchmeisser, author = {Kolanek, Krzysztof and Tallarida, Massimo and Schmeißer, Dieter}, title = {Atomic layer deposition of HfO2 investigated in situ by means of a noncontact atomic force microscopy}, language = {en} } @inproceedings{GehrlichOhsiekKleinetal., author = {Gehrlich, Lukas and Ohsiek, Susanne and Klein, M. and Geiss, M. and Friedemann, Michael and K{\"u}cher, Peter and Schmeißer, Dieter}, title = {Ultrathin TaN/Ta barrier modifications to fullfill next technology node requirements}, series = {2011 IEEE International Interconnect Technology Conference and 2011 Materials for Advanced Metallization (IITC/MAM 2011), Dresden, Germany, 8 - 12 May 2011}, booktitle = {2011 IEEE International Interconnect Technology Conference and 2011 Materials for Advanced Metallization (IITC/MAM 2011), Dresden, Germany, 8 - 12 May 2011}, publisher = {IEEE}, address = {Piscataway, NJ}, isbn = {978-1-4577-0503-8}, doi = {10.1109/IITC.2011.5940322}, pages = {82 -- 84}, language = {en} } @inproceedings{RichterFriedrichPhilipetal., author = {Richter, Matthias and Friedrich, Daniel and Philip, Shine and Paloumpa, Ioanna and M{\"u}ller, Klaus and Schmeißer, Dieter}, title = {Study of P3HT/PCBM based films by NEXAFS}, series = {Verhandlungen der Deutschen Physikalischen Gesellschaft, Reihe 6, Bd. 45}, booktitle = {Verhandlungen der Deutschen Physikalischen Gesellschaft, Reihe 6, Bd. 45}, publisher = {Deutsche Physikalische Gesellschaft}, address = {Bad Honnef}, issn = {0420-0195}, pages = {S. 194}, abstract = {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.}, language = {en} } @inproceedings{SchmidtSchmeisser, author = {Schmidt, Stephan and Schmeißer, Dieter}, title = {Cobalt/nickel mixed oxides - cathode materials for Li-Ion-Batteries}, series = {Verhandlungen der Deutschen Physikalischen Gesellschaft, Reihe 6, Bd. 45}, booktitle = {Verhandlungen der Deutschen Physikalischen Gesellschaft, Reihe 6, Bd. 45}, publisher = {Deutsche Physikalische Gesellschaft}, address = {Bad Honnef}, issn = {0420-0195}, pages = {S. 596}, abstract = {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.}, language = {en} } @inproceedings{MuellerChowdhuryDremovetal., author = {M{\"u}ller, P. and Chowdhury, F. and Dremov, V. and Koval, Yuri and Lichtenberg, F. and M{\"u}ller, S. and Schmeißer, Dieter and Pentcheva, R.}, title = {Resistive memory switching in perovskite-derivative single crystals}, series = {Verhandlungen der Deutschen Physikalischen Gesellschaft, Reihe 6, Bd. 43}, booktitle = {Verhandlungen der Deutschen Physikalischen Gesellschaft, Reihe 6, Bd. 43}, publisher = {Deutsche Physikalische Gesellschaft}, address = {Bad Honnef}, issn = {0420-0195}, pages = {S. 818}, abstract = {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.}, language = {en} } @misc{MuellerGoryachkoBurkovetal., author = {M{\"u}ller, K. and Goryachko, Andriy and Burkov, Yevgen and Schwiertz, Carola and Ratzke, Markus and K{\"o}ble, J. and Reif, J{\"u}rgen and Schmeißer, Dieter}, title = {Scanning Kelvin probe and photoemission electron microscopy of organic source-drain structures}, series = {Synthetic Metals}, volume = {146}, journal = {Synthetic Metals}, number = {3}, pages = {377 -- 382}, language = {en} } @misc{DasRichterTallaridaetal., author = {Das, Chittaranjan and Richter, Matthias and Tallarida, Massimo and Schmeißer, Dieter}, title = {Electronic properties of atomic layer deposited films, anatase and rutile TiO2 studied by resonant photoemission spectroscopy}, series = {Journal of Physics D: Applied Physics}, volume = {49}, journal = {Journal of Physics D: Applied Physics}, number = {27}, issn = {0022-3727}, doi = {10.1088/0022-3727/49/27/275304}, pages = {275304-1 -- 275304-17}, abstract = {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.}, language = {en} } @inproceedings{MuellerMilkoBurkovetal., author = {M{\"u}ller, Klaus and Milko, Sergey and Burkov, Yevgen and Schmeißer, Dieter}, title = {Mischkristalle des Systems ZnS-CuInS2 f{\"u}r multispektrale Solarzellen}, series = {Verhandlungen der Deutschen Physikalischen Gesellschaft}, booktitle = {Verhandlungen der Deutschen Physikalischen Gesellschaft}, publisher = {Deutsche Physikalische Gesellschaft}, address = {Bad Honnef}, abstract = {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 St{\"o}chiometrie mit spektroskopischen Methoden (XPS, UPS) studiert. Parallel dazu wurde das Verhalten von im Vakuum aufgedampften ZnS und die entsprechenden Oberfl{\"a}chenreaktionen in Abh{\"a}ngigkeit von der Temperatur untersucht und charakterisiert, so dass Aussagen {\"u}ber die Optimierung und Anpassung von Pr{\"a}parationsbedingungen und Parametern zur Herstellung von erstens reinem CIS und zweitens von Mischkristallen des Typs Zn2-xCuxInxS2 m{\"o}glich werden. Zwischen den beiden Endgliedern ZnS und CuInS2 besteht bis auf einen Phasen{\"u}bergang bei etwa 80\% CIS l{\"u}ckenlose Mischbarkeit gem{\"a}ss Zn2-xCuxInxS2 (Bente: Chem.Erde (1991)). Die elektronische Bandl{\"u}cke dieser Mischkristalle l{\"a}sst sich im Vergleich zu reinem CuInS2 in einem Bereich von 3,67 eV (ZnS) bis 1,55 eV (CuInS2) variieren. Damit besteht die M{\"o}glichkeit, durch kontrollierte {\"A}nderung der Zusammensetzung der Schichten die Effizienz von Solarzellen aus diesem Material zu optimieren.}, language = {de} } @inproceedings{HellerLopezBitzeretal., author = {Heller, Thomas and Lopez, Alberto and Bitzer, Thomas and Richardson, Neville V. and Schmeißer, Dieter}, title = {The Adsorption of Maleic Anhydride on Si(100)-2x1: A Combined HREELS and NEXAFS Study}, series = {Verhandlungen der Deutschen Physikalischen Gesellschaft}, booktitle = {Verhandlungen der Deutschen Physikalischen Gesellschaft}, publisher = {Deutsche Physikalische Gesellschaft}, address = {Bad Honnef}, abstract = {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.}, language = {en} } @inproceedings{HoffmannMikaloSchmeisseretal., author = {Hoffmann, Patrick and Mikalo, Ricardo Pablo and Schmeißer, Dieter and Kittler, Martin}, title = {Spektro-Mikroskopie auf multikristallinem Silizium}, series = {Verhandlungen der Deutschen Physikalischen Gesellschaft}, booktitle = {Verhandlungen der Deutschen Physikalischen Gesellschaft}, publisher = {Deutsche Physikalische Gesellschaft}, address = {Bad Honnef}, abstract = {Es werden spektro-mikroskopische Untersuchungen an multikristallinem Silizium (mc-Si) vorgestellt, einem aussichtsreichen Material f{\"u}r die Herstellung preiswerter Solarzellen. Dazu wird ein Photoemissions- Elektronenmikroskop (PEEM) ausgestattet mit einem zus{\"a}tzlichen Energieanalysator f{\"u}r Elektronen (µESCA) genutzt. Bei Verwendung eines Synchrotrons als Anregungsquelle ist es so m{\"o}glich, sowohl Absorbtions-Spektren (NEXAFS) als auch Photoelektronen-Spektren (PES) mit Ortsaufl{\"o}sung zu erhalten. Dabei wird gezeigt, dass das nat{\"u}rliche Oxid zur Untersuchung der morphologie-abh{\"a}ngigen Oberfl{\"a}chenpotentiale nicht entfernt werden muss. Des Weiteren wird die Verteilung von Ca- und Na-Ausscheidungen, die auf dem mc-Si gefunden wurden, durch ortsaufgel{\"o}stes NEXAFS bzw. PES dargestellt. F{\"u}r den Photoemissions-Prozess des mc-Si im PEEM wird ein Modell aufgestellt, welches Photoemission mit einer Quecksilberdampflampe (hνmax = 4,9 eV) erkl{\"a}rt.}, language = {de} } @inproceedings{MikaloAppelHoffmannetal., author = {Mikalo, Ricardo Pablo and Appel, G{\"u}nter and Hoffmann, Patrick and Schmeißer, Dieter}, title = {Conducting Polypyrrole doped with Phthalocyaninesulfonates - new materials for chemical sensors}, series = {Verhandlungen der Deutschen Physikalischen Gesellschaft}, booktitle = {Verhandlungen der Deutschen Physikalischen Gesellschaft}, publisher = {Deutsche Physikalische Gesellschaft}, address = {Bad Honnef}, abstract = {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.}, language = {en} } @inproceedings{HoffmannBoehmeSchmeisseretal., author = {Hoffmann, Patrick and B{\"o}hme, Oliver and Schmeißer, Dieter and Lloyd Spetz, Anita and M{\aa}rtenson, Per}, title = {Einfluß von Nanopartikeln auf die Funktion von Hochtemperatursensoren}, series = {Verhandlungen der Deutschen Physikalischen Gesellschaft}, booktitle = {Verhandlungen der Deutschen Physikalischen Gesellschaft}, publisher = {Deutsche Physikalische Gesellschaft}, address = {Bad Honnef}, abstract = {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 {\"u}berzogenen Nanoteilchen erkl{\"a}rt. Die unterschiedlich ausgepr{\"a}gten Dipol-Verschiebungen auf den einzelnen Proben erlaubten eine Erkl{\"a}rung der thermischen Vorbehandlung, die bei Weglassen zu „frischen" und je nach Temperatur zu „aktivierten" oder „toten" Sensoren f{\"u}hrte.}, language = {de} } @inproceedings{MikaloAppelHoffmannetal., author = {Mikalo, Ricardo Pablo and Appel, G{\"u}nter and Hoffmann, Patrick and Schmeißer, Dieter}, title = {Leitf{\"a}higes Polypyrrol als Elektrodenmaterial: Wechselwirkungen mit Silber}, series = {Verhandlungen der Deutschen Physikalischen Gesellschaft}, booktitle = {Verhandlungen der Deutschen Physikalischen Gesellschaft}, publisher = {Deutsche Physikalische Gesellschaft}, address = {Bad Honnef}, abstract = {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 leitf{\"a}hige Polymer, als auch das Silber ihren Leitf{\"a}higkeitsmechanismus beibehalten. Es konnte gezeigt werden, daß bei steigender Silberbelegung die Intensit{\"a}t der Polaronenzust{\"a}nde des Polypyrrol in st{\"a}rkerem Maße abnimmt, als die Intensit{\"a}t der unbesetzten Zust{\"a}nde. Das l{\"a}ßt darauf schließen, daß Silber die Grenzfl{\"a}che stabilisiert.}, language = {de} } @inproceedings{HellerBoehmeSchmeisser, author = {Heller, Thomas and B{\"o}hme, Oliver and Schmeißer, Dieter}, title = {Gap - Zust{\"a}nde in Wolframoxid WO3 - relaxierten Oberfl{\"a}chen}, series = {Verhandlungen der Deutschen Physikalischen Gesellschaft}, booktitle = {Verhandlungen der Deutschen Physikalischen Gesellschaft}, publisher = {Deutsche Physikalische Gesellschaft}, address = {Bad Honnef}, abstract = {Vorgestellt werden Arbeiten an d{\"u}nnen WO3-Schichten, die durch Verdampfen aus einer Knudsenzelle im UHV pr{\"a}pariert wurden. Diese Filme sind im Rahmen der XPS-Analysen st{\"o}chiometrisch, ohne Gap-Zust{\"a}nde. Definierte Gap-Zust{\"a}nde bilden sich durch Relaxierung der Oberfl{\"a}che: nach einigen Stunden im UHV, nach Heizen in Argon-Atmosph{\"a}re und nach Belegung mit Natrium. Die Charakterisierung dieser definierten Wolframoxid-Schichten erfolgt durch: 1.)XPS-Intensit{\"a}ten 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-Zust{\"a}nden in der Bandl{\"u}cke}, language = {de} } @inproceedings{HoffmannMikaloSchmeisser, author = {Hoffmann, Patrick and Mikalo, Ricardo Pablo and Schmeißer, Dieter}, title = {PEEM-Untersuchung an Spaltfl{\"a}chen von MoTe2-(0001)}, series = {Verhandlungen der Deutschen Physikalischen Gesellschaft}, booktitle = {Verhandlungen der Deutschen Physikalischen Gesellschaft}, publisher = {Deutsche Physikalische Gesellschaft}, address = {Bad Honnef}, abstract = {Molybd{\"a}nditellurid (MoTe2) geh{\"o}rt 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)-Spaltfl{\"a}chen mit einem Photoemissions-Elektronenmikroskop (PEEM) untersucht. Diese Untersuchung erbrachte nebeneinander auf den Proben- oberfl{\"a}chen liegende stark kontrastierte helle und dunkle Bereiche. Da das PEEM Austrittsarbeitsunterschiede als Kontrast darstellt, k{\"o}nnen diese hellen und dunklen Bereiche auf lokale Unterschiede in der Austrittsarbeit zur{\"u}ckgef{\"u}hrt werden. Weiterhin wird {\"u}ber den Versuch berichtet, eine Zuordnung zwischen dem Kontrast und dem Unterschied in der Austrittsarbeit mit Hilfe eines Elektronenenergie-Analysators (micro-ESCA) zu treffen.}, language = {de} } @inproceedings{ŁobazaKotSchmeisser, author = {Łobaza, Justyna and Kot, Małgorzata and Schmeißer, Dieter}, title = {Analysis of surface oxidation of TiON ALD films}, series = {Verhandlungen der Deutschen Physikalischen Gesellschaft}, booktitle = {Verhandlungen der Deutschen Physikalischen Gesellschaft}, publisher = {Deutsche Physikalische Gesellschaft}, address = {Bad Honnef}, issn = {0420-0195}, pages = {S. 202}, abstract = {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).}, language = {en} } @misc{SchmeisserJanowitz, author = {Schmeißer, Dieter and Janowitz, Christoph}, title = {Two polarization dependent Auger decays observed by resonant photoelectron spectroscopy at the Cu2p-edge of superconducting BiSrCu-oxides}, series = {Nuclear Instruments and Methods in Physics Research B}, volume = {411}, journal = {Nuclear Instruments and Methods in Physics Research B}, issn = {0168-583X}, doi = {10.1016/j.nimb.2017.01.084}, pages = {53 -- 56}, abstract = {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).}, language = {en} } @inproceedings{GarainHenkelMandaletal., author = {Garain, Samiran and Henkel, Karsten and Mandal, Dipankar and Schmeißer, Dieter}, title = {One-Pot Synthesis of Copper Oxide Nanowires and PVDF/CuO Composite Films for Piezoelectric Energy Harvesting Application}, series = {Verhandlungen der Deutschen Physikalischen Gesellschaft, Reihe 6, Band 53,3}, booktitle = {Verhandlungen der Deutschen Physikalischen Gesellschaft, Reihe 6, Band 53,3}, publisher = {Deutsche Physikalische Gesellschaft}, address = {Bad Honnef}, issn = {0420-0195}, pages = {S. 135}, abstract = {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.}, language = {en} } @inproceedings{KotNaumannGarainetal., author = {Kot, Małgorzata and Naumann, Franziska and Garain, Samiran and Po{\'{z}}arowska, Emilia and Gargouri, Hassan and Henkel, Karsten and Schmeißer, Dieter}, title = {Aluminum nitride films prepared by plasma atomic layer deposition using different plasma sources}, series = {Verhandlungen der Deutschen Physikalischen Gesellschaft, Reihe 6, Band 53,3}, booktitle = {Verhandlungen der Deutschen Physikalischen Gesellschaft, Reihe 6, Band 53,3}, publisher = {Deutsche Physikalische Gesellschaft}, address = {Bad Honnef}, issn = {0420-0195}, pages = {S. 170}, abstract = {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 {\AA}/cycle.}, language = {en} } @inproceedings{KotKegelmannKusetal., author = {Kot, Małgorzata and Kegelmann, Lukas and Kus, Peter and Tsud, Nataliya and Matol{\´i}nov{\´a}, Iva and Albrecht, Steve and Matolin, Vladimir and Schmeißer, Dieter}, title = {Room temperature atomic layer deposition for perovskite solar cells}, series = {Verhandlungen der Deutschen Physikalischen Gesellschaft, Reihe 6, Band 53,3}, booktitle = {Verhandlungen der Deutschen Physikalischen Gesellschaft, Reihe 6, Band 53,3}, publisher = {Deutsche Physikalische Gesellschaft}, address = {Bad Honnef}, issn = {0420-0195}, pages = {S. 174}, abstract = {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.}, language = {en} } @incollection{SchmeisserKotCorreaetal., author = {Schmeißer, Dieter and Kot, Małgorzata and Corr{\^e}a, Silma Alberton and Das, Chittaranjan and Henkel, Karsten}, title = {Interface Potentials, Intrinsic Defects, and Passivation Mechanisms in Al₂O₃, HfO₂, and TiO₂ Ultrathin Films}, series = {Encyclopedia of Interfacial Chemistry: Surface Science and Electrochemistry, vol. 3.1}, booktitle = {Encyclopedia of Interfacial Chemistry: Surface Science and Electrochemistry, vol. 3.1}, editor = {Wandelt, Klaus}, publisher = {Elsevier}, address = {Oxford}, isbn = {978-0-12-809739-7}, doi = {10.1016/B978-0-12-409547-2.14119-8}, pages = {162 -- 171}, abstract = {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.}, language = {en} } @misc{BiswasGarainMaityetal., author = {Biswas, Anirban and Garain, Samiran and Maity, Kuntal and Henkel, Karsten and Schmeißer, Dieter and Mandal, Dipankar}, title = {Influence of In situ Synthesized Bismuth Oxide Nanostructures in Self-poled PVDF-based Nanogenerator for Mechanical Energy Harvesting Application}, series = {Polymer Composites}, volume = {40}, journal = {Polymer Composites}, number = {S1}, issn = {0272-8397}, doi = {10.1002/pc.24628}, pages = {E265 -- E274}, abstract = {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.}, language = {en} } @misc{DasKotHellmannetal., author = {Das, Chittaranjan and Kot, Małgorzata and Hellmann, Tim and Wittich, Carolin and Mankel, Eric and Zimmermann, Iwan and Schmeißer, Dieter and Nazeeruddin, Mohammad Khaja and Jaegermann, Wolfram}, title = {Atomic Layer-Deposited Aluminum Oxide Hinders Iodide Migration and Stabilizes Perovskite Solar Cells}, series = {Cell Reports Physical Science}, volume = {1}, journal = {Cell Reports Physical Science}, number = {7}, issn = {2666-3864}, doi = {10.1016/j.xcrp.2020.100112}, pages = {18}, abstract = {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.}, language = {en} } @misc{KotKegelmannKoebleretal., author = {Kot, Małgorzata and Kegelmann, Lukas and K{\"o}bler, Hans and Vorokhta, Mykhailo and Escudero, Carlos and K{\´u}š, Peter and Šm{\´i}d, Břetislav and Tallarida, Massimo and Albrecht, Steve and Abate, Antonio and Matol{\´i}nov{\´a}, Iva and Schmeißer, Dieter and Flege, Jan Ingo}, title = {In situ Near-Ambient Pressure X-ray Photoelectron Spectroscopy Reveals the Influence of Photon Flux and Water on the Stability of Halide Perovskite}, series = {ChemSusChem}, volume = {13}, journal = {ChemSusChem}, number = {21}, issn = {1864-5631}, doi = {10.1002/cssc.202001527}, pages = {5722 -- 5730}, abstract = {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.}, language = {en} } @misc{GhoshSinhaXieetal., author = {Ghosh, Sujoy Kumar and Sinha, Tridib Kumar and Xie, Mengying and Bowen, Christopher Rhys and Garain, Samiran and Mahanty, Biswajit and Roy, Krittish and Henkel, Karsten and Schmeißer, Dieter and Kim, Jin Kuk and Mandal, Dipankar}, title = {Temperature-Pressure Hybrid Sensing All-Organic Stretchable Energy Harvester}, series = {ACS Applied Electronic Materials}, volume = {3}, journal = {ACS Applied Electronic Materials}, number = {1}, issn = {2637-6113}, doi = {10.1021/acsaelm.0c00816}, pages = {248 -- 259}, abstract = {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.}, language = {en} } @misc{SchmeisserMuellerHenkel, author = {Schmeißer, Dieter and M{\"u}ller, Klaus and Henkel, Karsten}, title = {Photosensitive and Rectifying Properties of Ga2O3 Described by Polaronic Screened Electrons and Internal Potentials}, series = {Journal of Physical Chemistry C}, volume = {127}, journal = {Journal of Physical Chemistry C}, number = {47}, issn = {1932-7447}, doi = {10.1021/acs.jpcc.3c05785}, pages = {23077 -- 23089}, abstract = {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.}, language = {en} } @misc{HenkelOpreaPaloumpaetal., author = {Henkel, Karsten and Oprea, A. and Paloumpa, Ioanna and Appel, G{\"u}nter and Schmeißer, Dieter and Kamieth, P.}, title = {Selective polypyrrole electrodes for quartz microbalances : NO2 and gas flux sensitivities}, series = {Sensors and Actuators : B, Chemical 76(2001)1-3}, volume = {76}, journal = {Sensors and Actuators : B, Chemical 76(2001)1-3}, number = {1-3}, issn = {0925-4005}, pages = {124 -- 129}, language = {en} } @inproceedings{BatchelorHoffmannSchmeisseretal., author = {Batchelor, David R. and Hoffmann, Patrick and Schmeißer, Dieter and Hulea, Iulian and Brinza, Monica}, title = {The Al-Fe interface of friction-welded joints}, series = {Verhandlungen der Deutschen Physikalischen Gesellschaft}, booktitle = {Verhandlungen der Deutschen Physikalischen Gesellschaft}, publisher = {Deutsche Physikalische Gesellschaft}, address = {Bad Honnef}, abstract = {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.}, language = {en} } @inproceedings{RachowHagendorfMuelleretal., author = {Rachow, Fabian and Hagendorf, Moritz and M{\"u}ller, Klaus and Schmeißer, Dieter}, title = {Synthesis of Methanol from CO2 for Power-to-Liquid applications}, series = {Verhandlungen der Deutschen Physikalischen Gesellschaft}, booktitle = {Verhandlungen der Deutschen Physikalischen Gesellschaft}, publisher = {Deutsche Physikalische Gesellschaft}, address = {Bad Honnef}, pages = {S. 256}, abstract = {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.}, language = {en} } @inproceedings{HenkelKotSchmeisser, author = {Henkel, Karsten and Kot, Małgorzata and Schmeißer, Dieter}, title = {Localized defect states and charge trapping in Al₂O₃ films prepared by atomic layer deposition}, series = {Verhandlungen der Deutschen Physikalischen Gesellschaft}, booktitle = {Verhandlungen der Deutschen Physikalischen Gesellschaft}, publisher = {Deutsche Physikalische Gesellschaft}, address = {Bad Honnef}, issn = {0420-0195}, pages = {S. 205}, abstract = {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.}, language = {en} } @misc{RichterChengCrumlinetal., author = {Richter, Matthias R. and Cheng, Wen-Hui and Crumlin, Ethan J. and Drisdell, Walter S. and Atwater, Harry A. and Schmeißer, Dieter and Lewis, Nathan S. and Brunschwig, Bruce S.}, title = {X‑ray Photoelectron Spectroscopy and Resonant X‑ray Spectroscopy Investigations of Interactions between Thin Metal Catalyst Films and Amorphous Titanium Dioxide Photoelectrode Protection Layers}, series = {Chemistry of Materials}, volume = {33}, journal = {Chemistry of Materials}, number = {4}, issn = {0897-4756}, doi = {10.1021/acs.chemmater.0c04043}, pages = {1265 -- 1275}, abstract = {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.}, language = {en} } @inproceedings{KotWojciechowskiSnaithetal., author = {Kot, Małgorzata and Wojciechowski, Konrad and Snaith, Henry J. and Schmeißer, Dieter}, title = {Characterization of the perovskite solar cells containing atomic layer deposited Al2O3 buffer layer}, series = {Verhandlungen der Deutschen Physikalischen Gesellschaft e.V.}, booktitle = {Verhandlungen der Deutschen Physikalischen Gesellschaft e.V.}, publisher = {Deutsche Physikalische Gesellschaft}, address = {Bad Honnef}, issn = {0420-0195}, pages = {S. 147}, abstract = {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.}, language = {en} } @inproceedings{IsraelRachowSchwiertzetal., author = {Israel, Johannes and Rachow, Fabian and Schwiertz, Carola and Charlafti, Evgenia and M{\"u}ller, Klaus and Schmeißer, Dieter}, title = {Direct CO2-Methanation of flue gas emitted by conventional power plants}, series = {Verhandlungen der Deutschen Physikalischen Gesellschaft}, booktitle = {Verhandlungen der Deutschen Physikalischen Gesellschaft}, publisher = {Deutsche Physikalische Gesellschaft}, address = {Bad Honnef}, pages = {S. 255}, abstract = {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.}, language = {en} } @incollection{MuellerIsraelRachowetal., author = {M{\"u}ller, Klaus and Israel, Johannes and Rachow, Fabian and Schmeißer, Dieter}, title = {Sabatier-Based Direct Synthesis of Methane and Methanol Using CO2 from Industrial Gas Mixtures}, series = {Engineering Solutions for CO2 Conversion}, booktitle = {Engineering Solutions for CO2 Conversion}, editor = {Ramirez Reina, Tomas and Odriozola, Jos{\´e} Antonio and Arellano-Garcia, Harvey}, edition = {1}, publisher = {Wiley-VCH}, address = {Weinheim}, isbn = {978-3-527-34639-4}, pages = {253 -- 280}, language = {en} } @misc{MahmoodinezhadJanowitzNaumannetal., author = {Mahmoodinezhad, Ali and Janowitz, Christoph and Naumann, Franziska and Plate, Paul and Gargouri, Hassan and Henkel, Karsten and Schmeißer, Dieter and Flege, Jan Ingo}, title = {Low-temperature growth of gallium oxide thin films by plasma-enhanced atomic layer deposition}, series = {Journal of Vacuum Science and Technology A}, volume = {38}, journal = {Journal of Vacuum Science and Technology A}, number = {2}, issn = {0734-2101}, doi = {10.1116/1.5134800}, abstract = {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 {\AA} 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.}, language = {en} } @misc{MaityGarainHenkeletal., author = {Maity, Kuntal and Garain, Samiran and Henkel, Karsten and Schmeißer, Dieter and Mandal, Dipankar}, title = {Self-Powered Human-Health Monitoring through Aligned PVDFNanofibers Interfaced Skin-Interactive Piezoelectric Sensor}, series = {ACS Applied Polymer Materials}, volume = {2}, journal = {ACS Applied Polymer Materials}, number = {2}, issn = {2637-6105}, doi = {10.1021/acsapm.9b00846}, pages = {862 -- 878}, abstract = {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.}, language = {en} } @misc{KotVorokhtaWangetal., author = {Kot, Małgorzata and Vorokhta, Mykhailo and Wang, Zhiping and Snaith, Henry J. and Schmeißer, Dieter and Flege, Jan Ingo}, title = {Thermal stability of CH3NH3PbIxCl3-x versus [HC(NH2)2]0.83Cs0.17PbI2.7Br0.3 perovskite films by X-ray photoelectron spectroscopy}, series = {Applied Surface Science}, volume = {513}, journal = {Applied Surface Science}, issn = {0169-4332}, doi = {10.1016/j.apsusc.2020.145596}, pages = {7}, abstract = {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.}, language = {en} } @misc{KotHenkelNaumannetal., author = {Kot, Małgorzata and Henkel, Karsten and Naumann, Franziska and Gargouri, Hassan and Tarnawska, Lidia Lupina and Wilker, Viola and Kus, Peter and Pożarowska, Emilia and Garain, Samiran and Rouissi, Zied and Schmeißer, Dieter}, title = {Comparison of plasma-enhanced atomic layer deposition AlN films prepared with different plasma sources}, series = {Journal of Vacuum Science and Technology A}, volume = {37}, journal = {Journal of Vacuum Science and Technology A}, number = {2}, issn = {0734-2101}, doi = {10.1116/1.5079628}, pages = {11}, abstract = {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 {\AA}/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).}, language = {en} } @misc{KotwicaDomaradzkiWojcieszaketal., author = {Kotwica, Tomasz and Domaradzki, Jarosław and Wojcieszak, Damian and Sikora, Andrzej and Kot, Małgorzata and Schmeißer, Dieter}, title = {Analysis of surface properties of Ti-Cu-Ox gradient thin films using AFM and XPS investigations}, series = {Materials Science-Poland}, volume = {36}, journal = {Materials Science-Poland}, number = {4}, issn = {0137-1339}, doi = {10.2478/msp-2018-0100}, pages = {761 -- 768}, abstract = {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.}, language = {en} } @misc{JanowitzSchmeisser, author = {Janowitz, Christoph and Schmeißer, Dieter}, title = {Out-of-plane electronic contributions in Bi-cuprates studied by resonant photoelectron spectroscopy at the Cu 2p edge}, series = {Verhandlungen der DPG}, journal = {Verhandlungen der DPG}, publisher = {Deutsche Physikalische Gesellschaft}, address = {Bad Honnef}, issn = {0420-0195}, pages = {403 -- 403}, abstract = {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)}, language = {en} } @misc{MahmoodinezhadPożarowskaHenkeletal., author = {Mahmoodinezhad, Ali and Pożarowska, Emilia and Henkel, Karsten and Schmeißer, Dieter and Flege, Jan Ingo}, title = {Depth profiling of PEALD-AlN films based on Al2p XPS peak decomposition}, series = {Verhandlungen der DPG}, journal = {Verhandlungen der DPG}, publisher = {Deutsche Physikalische Gesellschaft}, address = {Bad Honnef}, issn = {0420-0195}, pages = {157 -- 157}, abstract = {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.}, language = {en} } @misc{ObstarczykKaczmarekWojcieszaketal., author = {Obstarczyk, Agata and Kaczmarek, Danuta and Wojcieszak, Damian and Mazur, Michał and Domaradzki, Jarosław and Kotwica, Tomasz and Pastuszek, Roman and Schmeißer, Dieter and Mazur, Piotr and Kot, Małgorzata}, title = {Tailoring optical and electrical properties of thin-film coatings based on mixed Hf and Ti oxides for optoelectronic application}, series = {Materials and Design}, volume = {175}, journal = {Materials and Design}, issn = {0264-1275}, doi = {10.1016/j.matdes.2019.107822}, pages = {15}, abstract = {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.}, language = {en} } @misc{RoyGhoshSultanaetal., author = {Roy, Krittish and Ghosh, Sujoy Kumar and Sultana, Ayesha and Garain, Samiran and Xie, Mengying and Bowen, Christopher Rhys and Henkel, Karsten and Schmeißer, Dieter and Mandal, Dipankar}, title = {A Self-Powered Wearable Pressure Sensor and Pyroelectric Breathing Sensor Based on GO Interfaced PVDF Nanofibers}, series = {ACS Applied Nano Materials}, volume = {2}, journal = {ACS Applied Nano Materials}, number = {4}, issn = {2574-0970}, doi = {10.1021/acsanm.9b00033}, pages = {2013 -- 2025}, abstract = {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.}, language = {en} } @misc{MuellerRachowGuentheretal., author = {M{\"u}ller, Klaus and Rachow, Fabian and G{\"u}nther, Vivien and Schmeißer, Dieter}, title = {Methanation of Coke Oven Gas with Nickel-based catalysts}, series = {International Journal of Environmental Science}, journal = {International Journal of Environmental Science}, number = {4}, issn = {2367-8941}, pages = {73 -- 79}, abstract = {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.}, language = {en} } @misc{KotHenkelMuelleretal., author = {Kot, Małgorzata and Henkel, Karsten and M{\"u}ller, Klaus and Kegelmann, Lukas and Albrecht, Steve and Tsud, Nataliya and K{\´u}s, Peter and Matolinov{\´a}, Iva and Schmeißer, Dieter}, title = {Al2O3-Atomic Layer Deposited Films on CH3NH3PbI3 : Intrinsic Defects and Passivation Mechanisms}, series = {Energy Technology , The Journal of Physical Chemistry C}, volume = {7}, journal = {Energy Technology , The Journal of Physical Chemistry C}, number = {11}, issn = {2194-4288}, doi = {10.1002/ente.201900975}, pages = {10}, abstract = {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.}, language = {en} } @misc{SchmeisserHenkelPożarowskaetal., author = {Schmeißer, Dieter and Henkel, Karsten and Pożarowska, Emilia and Kegelmann, Lukas and Tsud, Nataliya and Kot, Małgorzata}, title = {Point Defect-Mediated Interface Formation and Appearance of a Cooper Minimum for AlOₓ Atomic-Layer-Deposited Films on CH₃NH₃PbI₃}, series = {The Journal of Physical Chemistry. C}, volume = {123}, journal = {The Journal of Physical Chemistry. C}, number = {38}, issn = {1932-7447}, doi = {10.1021/acs.jpcc.9b05282}, pages = {23352 -- 23360}, abstract = {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.}, language = {en} } @misc{SchmeisserHenkel, author = {Schmeißer, Dieter and Henkel, Karsten}, title = {Intrinsic defects and multiple-atom processes in the oxidic semiconductor Ga₂O₃}, series = {Journal of Applied Physics}, volume = {123}, journal = {Journal of Applied Physics}, number = {16}, issn = {0021-8979}, doi = {10.1063/1.5010740}, pages = {161596-1 -- 161596-9}, abstract = {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.}, language = {en} } @misc{DorpNynsCuypersetal., author = {Dorp, Dennis H. von and Nyns, Laura and Cuypers, Daniel and Ivanov, Tsvetan and Brizzi, Simone and Tallarida, Massimo and Fleischmann, Claudia and H{\"o}nicke, Philipp and M{\"u}ller, Matthias and Richard, Olivier and Schmeißer, Dieter and De Gendt, Stefan and Lin, Dennis H. C. and Adelmann, Christoph}, title = {Amorphous Gadolinium Aluminate as a Dielectric and Sulfur for Indium Phosphide Passivation}, series = {ACS Applied Electronic Materials}, volume = {1}, journal = {ACS Applied Electronic Materials}, number = {11}, issn = {2637-6113}, doi = {10.1021/acsaelm.9b00388}, pages = {2190 -- 2201}, abstract = {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.}, language = {en} } @misc{JanowitzSchmeisser, author = {Janowitz, Christoph and Schmeißer, Dieter}, title = {Significance of out-of-plane electronic contributions in Bi-cuprates studied by resonant photoelectron spectroscopy at the Cu2p-edge}, series = {Superconductor Science and Technology}, volume = {31}, journal = {Superconductor Science and Technology}, number = {4}, issn = {0953-2048}, doi = {10.1088/1361-6668/aaadf6}, pages = {11}, abstract = {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.}, language = {en} } @misc{KotŁobazaNaumannetal., author = {Kot, Małgorzata and Łobaza, Justyna and Naumann, Franziska and Gargouri, Hassan and Henkel, Karsten and Schmeißer, Dieter}, title = {Long-term ambient surface oxidation of titanium oxynitride films prepared by plasma-enhanced atomic layer deposition: An XPS study}, series = {Journal of Vacuum Science and Technology A}, volume = {36}, journal = {Journal of Vacuum Science and Technology A}, number = {1}, issn = {0734-2101}, doi = {10.1116/1.5003356}, abstract = {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.}, language = {en} } @misc{GarainSenHenkeletal., author = {Garain, Samiran and Sen, Shrabanee and Henkel, Karsten and Schmeißer, Dieter and Mandal, Dipankar}, title = {Enhancement of Electroactive β-phase and Superior Dielectric Properties in Cerium Based Poly(vinylidene fluoride) Composite Films}, series = {Materials Today: proceedings}, volume = {5}, journal = {Materials Today: proceedings}, number = {3 part 3}, issn = {2214-7853}, doi = {10.1016/j.matpr.2017.11.003}, pages = {10084 -- 10090}, abstract = {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.}, language = {en} } @misc{KotWojciechowskiSnaithetal., author = {Kot, Małgorzata and Wojciechowski, Konrad and Snaith, Henry J. and Schmeißer, Dieter}, title = {Evidence of Nitrogen Contribution to the Electronic Structure of the CH₃NH₃PbI₃ Perovskite}, series = {Chemistry - A European Journal}, volume = {24}, journal = {Chemistry - A European Journal}, number = {14}, issn = {0947-6539}, doi = {10.1002/chem.201705144}, pages = {3539 -- 3544}, abstract = {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.}, language = {en} } @incollection{HenkelKotRichteretal., author = {Henkel, Karsten and Kot, Małgorzata and Richter, Matthias and Tallarida, Massimo and Schmeißer, Dieter}, title = {An (In Situ)² Approach: ALD and resPES Applied to Al₂O₃, HfO₂, and TiO₂ Ultrathin Films}, series = {Encyclopedia of Interfacial Chemistry: Surface Science and Electrochemistry, Vol. 3.1}, booktitle = {Encyclopedia of Interfacial Chemistry: Surface Science and Electrochemistry, Vol. 3.1}, editor = {Wandelt, Klaus}, publisher = {Elsevier}, address = {Oxford}, isbn = {978-0-12-809739-7}, doi = {10.1016/B978-0-12-409547-2.13852-1}, pages = {18 -- 26}, abstract = {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.}, language = {en} } @misc{MaityGarainHenkeletal., author = {Maity, Kuntal and Garain, Samiran and Henkel, Karsten and Schmeißer, Dieter and Mandal, Dipankar}, title = {Natural Sugar-Assisted, Chemically Reinforced, Highly Durable Piezoorganic Nanogenerator with Superior Power Density for Self-Powered Wearable Electronics}, series = {ACS Applied Materials \& Interfaces}, volume = {10}, journal = {ACS Applied Materials \& Interfaces}, issn = {1944-8244}, doi = {10.1021/acsami.8b15320}, pages = {44018 -- 44032}, abstract = {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.}, language = {en} } @misc{KotKegelmannDasetal., author = {Kot, Małgorzata and Kegelmann, Lukas and Das, Chittaranjan and Kus, Peter and Tsud, Nataliya and Matol{\´i}nov{\´a}, Iva and Albrecht, Steve and Matolin, Vladimir and Schmeißer, Dieter}, title = {Room temperature atomic layer deposited Al₂O₃ improves perovskite solar cells efficiency over time}, series = {ChemSusChem}, volume = {11}, journal = {ChemSusChem}, number = {20}, issn = {1864-5631}, doi = {10.1002/cssc.201801434}, pages = {3640 -- 3648}, abstract = {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.}, language = {en} } @misc{SchmeisserHenkelJanowitz, author = {Schmeißer, Dieter and Henkel, Karsten and Janowitz, Christoph}, title = {Ionicity of ZnO - a key system for transparent conductive oxides}, series = {epl : a letters journal exploring the frontiers of physics}, volume = {123}, journal = {epl : a letters journal exploring the frontiers of physics}, number = {2}, issn = {1286-4854}, doi = {10.1209/0295-5075/123/27003}, pages = {27003-p1 -- 27003-p7}, abstract = {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.}, language = {en} } @incollection{HenkelHaeberleMuelleretal., author = {Henkel, Karsten and Haeberle, J{\"o}rg and M{\"u}ller, Klaus and Janowitz, Christoph and Schmeißer, Dieter}, title = {Preparation, properties and electronic structure of SnO₂}, series = {Single Crystals of Electronic Materials}, booktitle = {Single Crystals of Electronic Materials}, editor = {Fornari, Robert}, publisher = {Elsevier, Woodhead Publishing}, address = {Duxford}, isbn = {978-0-08-102096-8}, pages = {547 -- 572}, abstract = {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.}, language = {en} } @misc{HenkelKotSchmeisser, author = {Henkel, Karsten and Kot, Małgorzata and Schmeißer, Dieter}, title = {Localized defect states and charge trapping in atomic layer deposited-Al₂O₃ films}, series = {Journal of Vacuum Science and Technology, A : Vacuum, Surfaces, and Films}, volume = {35}, journal = {Journal of Vacuum Science and Technology, A : Vacuum, Surfaces, and Films}, number = {1}, issn = {0734-2101}, doi = {10.1116/1.4971991}, pages = {01B125-1 -- 01B125-18}, abstract = {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.}, language = {de} } @misc{HenkelDasKotetal., author = {Henkel, Karsten and Das, Chittaranjan and Kot, Małgorzata and Schmeißer, Dieter and Naumann, Franziska and K{\"a}rkk{\"a}nen, Irina and Gargouri, Hassan}, title = {In-gap states in titanium dioxide and oxynitride atomic layer deposited films}, series = {Journal of Vacuum Science and Technology: A}, volume = {35}, journal = {Journal of Vacuum Science and Technology: A}, number = {1}, issn = {0734-2101}, doi = {10.1116/1.4972247}, pages = {01B135-1 -- 01B135-8}, abstract = {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.}, language = {en} } @misc{MenezesIndraDasetal., author = {Menezes, Prashanth W. and Indra, Arindam and Das, Chittaranjan and Walter, Carsten and G{\"o}bel, Caren and Gutkin, Vitaly and Schmeißer, Dieter and Driess, Matthias}, title = {Uncovering the Nature of Active Species of Nickel Phosphide Catalysts in High-Performance Electrochemical Overall Water Splitting}, series = {ACS Catalysis}, volume = {7}, journal = {ACS Catalysis}, number = {1}, issn = {2155-5435}, doi = {10.1021/acscatal.6b02666}, pages = {103 -- 109}, abstract = {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.}, language = {en} } @misc{MuellerRachowIsraeletal., author = {M{\"u}ller, Klaus and Rachow, Fabian and Israel, Johannes and Charlafti, Evgenia and Schwiertz, Carola and Schmeißer, Dieter}, title = {Direct Methanation of Flue Gas at a Lignite Power Plant}, series = {International Journal of Environmental Science}, journal = {International Journal of Environmental Science}, number = {2}, issn = {2367-8941}, pages = {425 -- 437}, abstract = {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.}, language = {en} } @misc{IndraMenezesDasetal., author = {Indra, Arindam and Menezes, Prashanth W. and Das, Chittaranjan and G{\"o}bel, Caren and Tallarida, Massimo and Schmeißer, Dieter and Driess, Matthias}, title = {A facile corrosion approach to the synthesis of highly active CoOxwater oxidation catalysts}, series = {Journal of Materials Chemistry A}, journal = {Journal of Materials Chemistry A}, number = {5}, issn = {2050-7488}, doi = {10.1039/c6ta10650a}, pages = {5171 -- 5177}, abstract = {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.}, language = {en} } @misc{KotHenkelDasetal., author = {Kot, Małgorzata and Henkel, Karsten and Das, Chittaranjan and Brizzi, Simone and K{\"a}rkk{\"a}nen, Irina and Schneidewind, Jessica and Naumann, Franziska and Gargouri, Hassan and Schmeißer, Dieter}, title = {Analysis of titanium species in titanium oxynitride films prepared by plasma enhanced atomic layer deposition}, series = {Surface and Coatings Technology}, volume = {324}, journal = {Surface and Coatings Technology}, issn = {0257-8972}, doi = {10.1016/j.surfcoat.2016.11.094}, pages = {586 -- 593}, abstract = {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.}, language = {en} } @misc{DasKotRouissietal., author = {Das, Chittaranjan and Kot, Małgorzata and Rouissi, Zied and Kędzierski, Kamil and Henkel, Karsten and Schmeißer, Dieter}, title = {Selective Deposition of an ultrathin Pt Layer on a Au-Nanoisland-Modified Si Photocathode for Hydrogen Generation}, series = {ACS Omega}, volume = {2}, journal = {ACS Omega}, number = {4}, issn = {2470-1343}, doi = {10.1021/acsomega.6b00374}, pages = {1360 -- 1366}, abstract = {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.}, language = {en} } @misc{KotDasHenkeletal., author = {Kot, Małgorzata and Das, Chittaranjan and Henkel, Karsten and Wojciechowski, Konrad and Snaith, Henry J. and Schmeißer, Dieter}, title = {Room temperature atomic layer deposited Al₂O₃ on CH₃NH₃PbI₃ characterized by synchrotron-based X-ray photoelectron spectroscopy}, series = {Nuclear Instruments and Methods in Physics Research B}, volume = {411}, journal = {Nuclear Instruments and Methods in Physics Research B}, issn = {0168-583X}, doi = {10.1016/j.nimb.2017.01.082}, pages = {49 -- 52}, abstract = {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.}, language = {en} } @misc{CibrevTallaridaDasetal., author = {Cibrev, Dejan and Tallarida, Massimo and Das, Chittaranjan and Lana-Villarreal, Teresa and Schmeißer, Dieter and Gómez, Roberto}, title = {New insights into water photooxidation on reductively pretreated hematite photoanodes}, series = {Physical Chemistry Chemical Physics}, volume = {19}, journal = {Physical Chemistry Chemical Physics}, number = {32}, issn = {1463-9076}, doi = {10.1039/C7CP03958A}, pages = {21807 -- 21817}, abstract = {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.}, language = {en} } @misc{BiswasHenkelSchmeisseretal., author = {Biswas, Anirban and Henkel, Karsten and Schmeißer, Dieter and Mandal, Dipankar}, title = {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}, series = {Phase Transitions}, volume = {90}, journal = {Phase Transitions}, number = {12}, issn = {0141-1594}, doi = {10.1080/01411594.2017.1337902}, pages = {1205 -- 1213}, abstract = {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.}, language = {en} } @misc{IndraMenezesDasetal., author = {Indra, Arindam and Menezes, Prashanth W. and Das, Chittaranjan and Schmeißer, Dieter and Driess, Matthias}, title = {Alkaline electrochemical water oxidation with multi-shelled cobalt manganese oxide hollow spheres}, series = {Chemical Communications}, volume = {53}, journal = {Chemical Communications}, number = {62}, issn = {1359-7345}, doi = {10.1039/C7CC03566G}, pages = {8641 -- 8644}, abstract = {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.}, language = {en} } @misc{AlbertonCorreaBrizziSchmeisser, author = {Alberton Corr{\^e}a, Silma and Brizzi, Simone and Schmeißer, Dieter}, title = {Spectroscopic investigation of the electronic structure of thin atomic layer deposition HfO2 films}, series = {Journal of Vacuum Science \& Technology A}, volume = {34}, journal = {Journal of Vacuum Science \& Technology A}, number = {1}, issn = {0734-2101}, doi = {10.1116/1.4935338}, pages = {01A117-1 -- 01A117-8}, abstract = {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.}, language = {en} } @misc{PitthandosReisAlbertonCorreaetal., author = {Pitthan, E. and dos Reis, R. and Alberton Corr{\^e}a, Silma and Schmeißer, Dieter and Boudinov, H. I. and Stedile, F. C.}, title = {Influence of CO annealing in metal-oxide-semiconductor capacitors with SiO2 films thermally grown on Si and on SiC}, series = {Journal of Applied Physics}, journal = {Journal of Applied Physics}, number = {119}, issn = {0021-8979}, doi = {10.1063/1.4939836}, pages = {025307-1 -- 025307-6}, abstract = {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.}, language = {en} } @misc{SowińskaHenkelSchmeisseretal., author = {Sowińska, Małgorzata and Henkel, Karsten and Schmeißer, Dieter and K{\"a}rkk{\"a}nen, Irina and Schneidewind, Jessica and Naumann, Franziska and Gruska, Bernd and Gargouri, Hassan}, title = {Plasma-enhanced atomic layer deposition of titanium oxynitrides films: A comparative spectroscopic and electrical study}, series = {Journal of Vacuum Science and Technology A}, journal = {Journal of Vacuum Science and Technology A}, number = {34}, issn = {0734-2101}, doi = {10.1116/1.4936227}, pages = {01A127-1 -- 01A127-9}, abstract = {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.}, language = {en} } @misc{GarainBarmanSinhaetal., author = {Garain, Samiran and Barman, Koushik and Sinha, Tridib Kumar and Jasimuddin, Sk and Haeberle, J{\"o}rg and Henkel, Karsten and Schmeißer, Dieter and Mandal, Dipankar}, title = {Cerium(III) Complex Modified Gold Electrode: An Efficient Electrocatalyst for the Oxygen Evolution Reaction}, series = {ACS Applied Materials and Interfaces}, volume = {8}, journal = {ACS Applied Materials and Interfaces}, number = {33}, issn = {1944-8244}, doi = {10.1021/acsami.6b05236}, pages = {21294 -- 21301}, abstract = {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.}, language = {en} } @misc{SowinskaBrizziDasetal., author = {Sowinska, Małgorzata and Brizzi, Simone and Das, Chittaranjan and K{\"a}rkk{\"a}nen, Irina and Schneidewind, Jessica and Naumann, Franziska and Gargouri, Hassan and Henkel, Karsten and Schmeißer, Dieter}, title = {Analysis of nitrogen species in titanium oxynitride ALD films}, series = {Applied Surface Science}, volume = {381}, journal = {Applied Surface Science}, issn = {0169-4332}, doi = {10.1016/j.apsusc.2016.02.096}, pages = {42 -- 47}, abstract = {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.}, language = {en} } @misc{SchmeisserHaeberle, author = {Schmeißer, Dieter and Haeberle, J{\"o}rg}, title = {Intrinsic localized gap states in IGZO and its parent single crystalline TCOs}, series = {Thin Solid Films}, journal = {Thin Solid Films}, number = {603}, issn = {0040-6090}, doi = {10.1016/j.tsf.2016.02.010}, pages = {206 -- 211}, abstract = {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.}, language = {en} } @misc{KrammZanaVoschetal., author = {Kramm, Ulrike Ingrid and Zana, Alessandro and Vosch, Tom and Fiechter, Sebastian and Arenz, Matthias and Schmeißer, Dieter}, title = {On the structural composition and stability of Fe-N-C catalysts prepared by an intermediate acid leaching}, series = {Journal of Solid State Electrochemistry}, volume = {20}, journal = {Journal of Solid State Electrochemistry}, number = {4}, issn = {1432-8488}, doi = {10.1007/s10008-015-3060-z}, pages = {969 -- 981}, abstract = {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-57M{\"o}ßbauer 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.}, language = {en} } @inproceedings{SowinskaDasWojciechowskietal., author = {Sowinska, Małgorzata and Das, Chittaranjan and Wojciechowski, Konrad and Snaith, Henry J. and Schmeißer, Dieter}, title = {XPS study of the ALD growth of Al₂O₃ on the CH₃NH₃PbI₃}, series = {Verhandlungen der Deutschen Physikalischen Gesellschaft}, booktitle = {Verhandlungen der Deutschen Physikalischen Gesellschaft}, publisher = {Deutsche Physikalische Gesellschaft}, address = {Bad Honnef}, pages = {S. 206}, abstract = {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.}, language = {en} } @inproceedings{DasTallaridaSchmeisser, author = {Das, Chittaranjan and Tallarida, Massimo and Schmeißer, Dieter}, title = {TiO2 laminated Silicon microstructures based stable photocathode for water splitting}, series = {Verhandlungen der Deutschen Physikalischen Gesellschaft}, booktitle = {Verhandlungen der Deutschen Physikalischen Gesellschaft}, publisher = {Deutsche Physikalische Gesellschaft}, address = {Bad Honnef}, pages = {S. 213}, abstract = {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}, language = {en} } @misc{HaeberleMachulikJanowitzetal., author = {Haeberle, J{\"o}rg and Machulik, Stephan and Janowitz, Christoph and Manzke, Recardo and Gaspar, Diana and Barquinha, Pedro and Schmeißer, Dieter}, title = {Gap states in the electronic structure of SnO2 single crystals and amorphous SnOxthin films}, series = {Journal of Applied Physics}, volume = {120}, journal = {Journal of Applied Physics}, number = {10}, issn = {0021-8979}, doi = {10.1063/1.4962313}, pages = {105101-1 -- 105101-13}, abstract = {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.}, language = {en} } @misc{SowinskaDasWojciechowskietal., author = {Sowinska, Małgorzata and Das, Chittaranjan and Wojciechowski, Konrad and Rouissi, Zied and Snaith, Henry J. and Schmeißer, Dieter}, title = {Atomic layer deposition of Al2O3 on CH3NH3PbI3 for enhancement of perovskite solar cells stability}, series = {Synchrotron Radiation in Natural Science : Bulletin of the Polish Synchrotron Radiation Society}, volume = {15}, journal = {Synchrotron Radiation in Natural Science : Bulletin of the Polish Synchrotron Radiation Society}, number = {1-2}, issn = {1644-7190}, pages = {S. 33}, language = {en} } @inproceedings{RouissiTallaridaSchmeisser, author = {Rouissi, Zied and Tallarida, Massimo and Schmeißer, Dieter}, title = {HfO2 grow by ALD on Si(111)-H terminated stepped surface}, series = {Verhandlungen der Deutschen Physikalischen Gesellschaft}, booktitle = {Verhandlungen der Deutschen Physikalischen Gesellschaft}, publisher = {Deutsche Physikalische Gesellschaft}, address = {Bad Honnef}, pages = {S. 419}, abstract = {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)}, language = {en} }