TY - CHAP A1 - Rachow, Fabian A1 - Hagendorf, Moritz A1 - Müller, Klaus A1 - Schmeißer, Dieter T1 - Synthesis of Methanol from CO2 for Power-to-Liquid applications T2 - Verhandlungen der Deutschen Physikalischen Gesellschaft N2 - The direct synthesis of methanol [CO2+3H2->CH3OH+H2O] represent a possibility to reduce the global CO2-emission by recycling the CO2 and also to store excess energy from renewable energy sources into a common fuel or chemical feedstock (Power-to-Liquid). For an acceptable conversion rate of CO2 a catalyst is needed, together with high temperatures (>200°C) and high pressure (50-200bar). Methanol is normally produced form synthesis gas, a mixture of CO and H2. By directly using CO2 for the exothermic reaction, we avoid the conversion of CO2 to CO by the reversed water gas shift reaction. We also present new concepts for the conversion from CO2-rich flue gases, eliminating the need for a separation of the CO2. The concept is backed up by measurements in laboratory scale. Here we use a Cu−ZnO catalyst on a ZrO2 substrate prepared by impregnation and compare the results with commercially available catalysts. We achieved a conversion of around 7% and a selectivity of 60% at a temperature of 240°C and 45bar. The reaction is thermodynamically limited with a maximum conversion rate of 15% at 250°C and 50bar. The conversion and the selectivity towards methanol is highly influenced by the catalyst used, the temperature, the pressure as well as the flow rate of the reactants. KW - direct methanol synthesis KW - power to liquide KW - Cu-ZnO catalyst KW - CO2 utilization Y1 - 2017 UR - http://www.dpg-verhandlungen.de/year/2017/conference/muenster/part/ake/session/8/contribution/5 SP - S. 256 PB - Deutsche Physikalische Gesellschaft CY - Bad Honnef ER - TY - GEN A1 - Das, Chittaranjan A1 - Kot, Małgorzata A1 - Rouissi, Zied A1 - Kędzierski, Kamil A1 - Henkel, Karsten A1 - Schmeißer, Dieter T1 - Selective Deposition of an ultrathin Pt Layer on a Au-Nanoisland-Modified Si Photocathode for Hydrogen Generation T2 - ACS Omega N2 - Platinum, being the most efficient and stable catalyst, is used in photoelectrochemical (PEC) devices. However, a minimal amount of Pt with maximum catalytic activity is required to be used to minimize the cost of production. In this work, we use an environmentally friendly, ost-effective, and less Pt-consuming method to prepare PEC devices for the hydrogen evolution reaction (HER). The Pt monolayer catalyst is selectively deposited on a Au-nanoisland-supported boron-doped p-type Si (100) photocathode. The PEC device based on the Si photocathode with an ultralow loading of the Pt catalyst exhibits a comparable performance for the HER to that of devices with a thick Pt layer. In addition, we demonstrate that by using a thin TiO2 layer deposited by atomic layer deposition photo-oxidation of the Si photocathode can be blocked resulting in a stable PEC performance. KW - water splitting KW - hydrogen evolution reaction (HER) KW - Si photocathode KW - gold nanoislands KW - nanostructured platinum Y1 - 2017 U6 - https://doi.org/10.1021/acsomega.6b00374 SN - 2470-1343 VL - 2 IS - 4 SP - 1360 EP - 1366 ER - TY - GEN A1 - Kot, Małgorzata A1 - Henkel, Karsten A1 - Das, Chittaranjan A1 - Brizzi, Simone A1 - Kärkkänen, Irina A1 - Schneidewind, Jessica A1 - Naumann, Franziska A1 - Gargouri, Hassan A1 - Schmeißer, Dieter T1 - Analysis of titanium species in titanium oxynitride films prepared by plasma enhanced atomic layer deposition T2 - Surface and Coatings Technology N2 - A comparative study of thin titanium oxynitride (TiOxNy) films prepared by plasma enhanced atomic layer deposition using tetrakis(dimethylamino)titanium (TDMAT) and N2 plasma as well as titanium(IV)isopropoxide and NH3 plasma is reported. The comparison is based on the combination of Ti2p core level and valence band spectroscopy and current-voltage measurements. The TDMAT/N2 process delivers generally higher fractions of TiN and TiON within the Ti2p spectra of the films and stronger photoemissions within the bandgap as resolved in detail by high energy resolution synchrotron-based spectroscopy. In particular, it is shown that higher TiN contributions and in-gap emission intensities correlate strongly with increased leakage currents within the films and might be modified by the process parameters and precursor selection. KW - Titanium oxynitride KW - Plasma enhanced atomic layer deposition (PEALD) KW - ALD process parameters KW - Ti-N contributions KW - In-gap defect states KW - Leakage current Y1 - 2017 U6 - https://doi.org/10.1016/j.surfcoat.2016.11.094 SN - 0257-8972 SN - 1879-3347 VL - 324 SP - 586 EP - 593 ER - TY - GEN A1 - Indra, Arindam A1 - Menezes, Prashanth W. A1 - Das, Chittaranjan A1 - Schmeißer, Dieter A1 - Driess, Matthias T1 - Alkaline electrochemical water oxidation with multi-shelled cobalt manganese oxide hollow spheres T2 - Chemical Communications N2 - Multi-shelled hollow spheres of cobalt manganese oxides (CMOs) deposited on Ni foam exhibited superior alkaline electrochemical water oxidation activity and surpassed those of bulk CMO and commercial noble metal-based catalysts. A higher amount of cobalt in the spinel structure resulted in the transformation of the tetragonal to the cubic phase with a decrease in the overpotential of oxygen evolution. KW - Water oxidation KW - Cobalt manganese oxides (CMOs) KW - Multi-shelled hollow spheres KW - Near-edge X-ray absorption fine structure (NEXAFS) KW - Cyclic voltammetry KW - Scanning electron microscopy Y1 - 2017 U6 - https://doi.org/10.1039/C7CC03566G SN - 1359-7345 SN - 1364-548X VL - 53 IS - 62 SP - 8641 EP - 8644 ER - TY - GEN A1 - Biswas, Anirban A1 - Henkel, Karsten A1 - Schmeißer, Dieter A1 - Mandal, Dipankar T1 - Comparison of the thermal stability of the α, β and γ phases in poly(vinylidene fluoride) based on in situ thermal Fourier transform infrared spectroscopy T2 - Phase Transitions N2 - The electroactive β phase of poly(vinylidenefluoride) (PVDF) is induced due to the aging time of PVDF solutions. The feasibility of the combination of the three crystalline polymorphs (α, β and γ) is demonstrated where their relative proportion within the PVDF film can be tailored by the simple monitoring of the preparation conditions. To identify all these phases, Fourier transform infrared (FT-IR) spectroscopy is carried out and it is spotlighted that the vibrational bands at 510 and 841 cm-1 are not sufficient to state the formation of the β phase. The main aim of this work is devoted to develop a better understanding on the thermal stability of these several phases of PVDF, which has a longstanding ambiguity persisting in this area. It has been found that the in situ thermal FT-IR spectroscopy is one of the best alternatives to understand this important issue. It is ascertained that the β phase is the least thermally stable phase among α, β and γ phases, whereas the γ phase is the most thermally stable phase. KW - PVDF KW - thermal stability KW - β-phase KW - infrared spectroscopy KW - in situ thermal FT-IR study Y1 - 2017 U6 - https://doi.org/10.1080/01411594.2017.1337902 SN - 0141-1594 SN - 1029-0338 VL - 90 IS - 12 SP - 1205 EP - 1213 ER - TY - GEN A1 - Cibrev, Dejan A1 - Tallarida, Massimo A1 - Das, Chittaranjan A1 - Lana-Villarreal, Teresa A1 - Schmeißer, Dieter A1 - Gómez, Roberto T1 - New insights into water photooxidation on reductively pretreated hematite photoanodes T2 - Physical Chemistry Chemical Physics N2 - It has been recently demonstrated that the photoactivity toward oxygen evolution of a number of n-type metal oxides can be substantially improved by a reductive electrochemical pretreatment. Such an enhancement has been primarily linked to the formation of low valent metal species that increase electrode conductivity. In this work, we report new insights into the electrochemical doping using highly ordered (110)-oriented hematite nanorods directly grown on FTO. The reductive pretreatment consists in applying negative potentials for a controlled period of time. Such a pretreatment was optimized in both potentiostatic and potentiodynamic regimes. We show that the optimized pretreatment enhances electrode conductivity due to an increase in charge carrier density. However, it additionally triggers changes in the morphologic, catalytic and electronic properties that facilitate the separation and collection of the photogenerated charge carriers causing an up to 8-fold enhancement in the photocurrent for water oxidation. The reductive pretreatment can be considered as a highly controllable electrochemical n-type doping with the amount of generated Fe2+/polaron species and the change in film morphology as the main factors determining the final efficiency for water photooxidation of the resulting electrodes. KW - hematite KW - photoanode KW - water oxidation KW - water splitting Y1 - 2017 U6 - https://doi.org/10.1039/C7CP03958A SN - 1463-9076 SN - 1463-9084 VL - 19 IS - 32 SP - 21807 EP - 21817 ER - TY - GEN A1 - Kot, Małgorzata A1 - Das, Chittaranjan A1 - Henkel, Karsten A1 - Wojciechowski, Konrad A1 - Snaith, Henry J. A1 - Schmeißer, Dieter T1 - Room temperature atomic layer deposited Al₂O₃ on CH₃NH₃PbI₃ characterized by synchrotron-based X-ray photoelectron spectroscopy T2 - Nuclear Instruments and Methods in Physics Research B N2 - An ultrathin Al₂O₃ film deposited on methylammonium lead triiodide (CH₃NH₃PbI₃) perovskite has the capability to suppress the carrier recombination process and improve the perovskite solar cells efficiency and stability. However, annealing at temperatures higher than 85°C degrades the CH₃NH₃PbI₃ perovskite film. The X-ray photoelectron spectroscopy study performed in this work indicates that it is possible to grow Al₂O₃ by atomic layer deposition on the perovskite at room temperature, however, besides pure Al₂O₃ some OH groups are found and the creation of lead and iodine oxides at the Al₂O₃/CH₃NH₃PbI₃ interface takes place. KW - Synchrotron-based X-ray photoelectron spectroscopy KW - Perovskite solar cells KW - Atomic layer deposition KW - Al₂O₃ Y1 - 2017 U6 - https://doi.org/10.1016/j.nimb.2017.01.082 SN - 0168-583X SN - 1872-9584 VL - 411 SP - 49 EP - 52 ER - TY - GEN A1 - Schmeißer, Dieter A1 - Janowitz, Christoph T1 - Two polarization dependent Auger decays observed by resonant photoelectron spectroscopy at the Cu2p-edge of superconducting BiSrCu-oxides T2 - Nuclear Instruments and Methods in Physics Research B N2 - We report on a resonant photoemission (resPES) study of PbxBi2-xSr2-yLayCan-1CunO2n+4+d (BISCO) single crystals to unravel the resonant decay mechanisms at the Cu2p absorption edge. The resPES studies on superconducting BISCO are performed at Bessy U49/2. We investigated BISCO single crystals with different hole doping concentrations at temperatures between 300 K and 17 K. CuO films have been used as a reference. We focus on the resPES data recorded at the Cu2p absorption edge. We find a strong polarization dependence for in-plane and out-of-plane geometries (with respect to the Cu-O plane) in our data which are caused by two independent Auger processes. We also report on the influence of different doping concentrations. Our resPES data enable us to sort the individual resonant mechanisms at the Cu2p edge in more detail than recently anticipated (Brookes et al., 2015). We discuss our data in the context of the recent discussion about the applicability of the Zhang-Rice model (Chen et al., 2013). KW - Synchrotron radiation KW - Superconductor KW - Cuprates KW - Resonant photoemission Y1 - 2017 U6 - https://doi.org/10.1016/j.nimb.2017.01.084 SN - 0168-583X SN - 1872-9584 VL - 411 SP - 53 EP - 56 ER - TY - GEN A1 - Müller, Klaus A1 - Bär, Werner A1 - Henkel, Karsten A1 - Jahnke, Agnes A1 - Schwiertz, Carola A1 - Schmeißer, Dieter T1 - Organische Feldeffekttransistoren als Transducer in der Biosensorik T1 - Organic Field Effect Transistors as Biosensors T2 - Technisches Messen N2 - In diesem Beitrag wird der Einsatz neuartiger Sensortypen für die medizinische Diagnostik beschrieben. Diese Sensoren sollen komplett organisch sein und auf dem Prinzip des Feldeffekttransistors basieren. Als Modellsystem für die Anwendung in der Biosensorik soll die Einsatzmöglichkeit dieser Sensoren in der nicht-invasiven Diagnostik der Helicobacter-pylori-Infektion überprüft werden. N2 - In this contribution we describe the investigation of new types of sensors in medical diagnosis. These sensors are completely organic and are based on the principle of organic field effect transistors. As model system for application in medical diagnosis we test the usability of this sensors for the diagnosis of helicobacter pylori. KW - Feldeffekttransistor KW - Biosensorik KW - Helicobacter pylori KW - Field effect transistors KW - biosensors KW - helicobacter pylori Y1 - 2003 U6 - https://doi.org/10.1524/teme.70.12.565.20261 SN - 0171-8096 VL - 70 IS - 12 SP - 565 EP - 568 ER - TY - GEN A1 - Müller, Klaus A1 - Rachow, Fabian A1 - Israel, Johannes A1 - Charlafti, Evgenia A1 - Schwiertz, Carola A1 - Schmeißer, Dieter T1 - Direct Methanation of Flue Gas at a Lignite Power Plant T2 - International Journal of Environmental Science N2 - The combustion of fossil fuels results in CO2 emission, which is one of the primary causes of global warming. An important approach for solving this problem is the fixation, the chemical utilization and the recycling of CO2. Therefore, we investigate the catalytic conversion of CO2 with H2 into methane (CH4) with an upscaled test station at a brown coal power plant. In a completely new strategy, we realize the direct conversion of the CO2 content of the flue gas, without a cleaning process like amine scrubbing or optimized combustion like oxyfuel. Our experiments are performed in matters of catalytic performance, heat production and stability of the catalytic Sabatier process, as a function of the gas flow rate. The catalytic performance is investigated with a simulated composition of flue gas and under real conditions directly at the power plant. The CH4 production by the Sabatier process is realized with a maximum input flow rate of near 50Nm3/h, with 30Nm3/h flue gas and 20Nm3/h hydrogen. For these values, the necessary power scale for hydrogen generation by electrolysis is around 100kW. With synthetic and real flue gas, a conversion up to 99% (for hydrogen surplus) with 100% selectivity is stabilized. The reaction operates in thermal steady state equilibrium without any external energy supply. In consequence, the process of CO2 recycling could be integrated directly as a post combustion process of conventional power plants, without an expensive capturing step, for example. KW - CO2 recycling KW - Power to Gas (PtG) KW - Synthetic Natural Gas (SNG) KW - Sabatier-Reaction KW - Flue Gas Y1 - 2017 UR - http://www.iaras.org/iaras/home/caijes/direct-methanation-of-flue-gas-at-a-lignite-power-plant SN - 2367-8941 IS - 2 SP - 425 EP - 437 ER - TY - GEN A1 - Kot, Małgorzata A1 - Łobaza, Justyna A1 - Naumann, Franziska A1 - Gargouri, Hassan A1 - Henkel, Karsten A1 - Schmeißer, Dieter T1 - Long-term ambient surface oxidation of titanium oxynitride films prepared by plasma-enhanced atomic layer deposition: An XPS study T2 - Journal of Vacuum Science and Technology A N2 - The surface oxidation of a titanium oxynitride (TiOxNy) film after long-time storage of 25 month in ambient conditions is investigated. The TiOxNy film is prepared by plasma-enhanced atomic layer deposition using etrakis(dimethylamino)titanium and nitrogen plasma, and the film is characterized by Ar+ ion sputtering of the film surface in combination with x-ray photoelectron spectroscopy (XPS) as well as by angle-resolved XPS. The total thickness of an oxygen-enriched layer at the surface of the TiOxNy films is found to be about 0.7 nm and it consists of a sequence of a 0.4 nm thick TiON/TiO2 enriched layer followed by a 0.3 nm thick TiO2 enriched layer underneath compared to the bulk composition of the film which shows constant values of 29% TiN, 29% TiO2, and 42% TiON. The results suggest that the TiON enrichment takes place initially at the surface followed by a surface and subsurface oxidation. KW - atomic layer deposition (ALD) KW - surface oxidation KW - X-Ray photoelectron spectroscopy (XPS) KW - titanium oxynitride Y1 - 2018 U6 - https://doi.org/10.1116/1.5003356 SN - 0734-2101 SN - 1520-8559 VL - 36 IS - 1 ER - TY - GEN A1 - Schmeißer, Dieter A1 - Henkel, Karsten T1 - Intrinsic defects and multiple-atom processes in the oxidic semiconductor Ga₂O₃ T2 - Journal of Applied Physics N2 - We report on the electronic structure of gallium oxide (Ga₂O₃) single crystals as studied by resonant photoelectron spectroscopy (resPES). We identify intrinsic electronic defects that are formed by mixed-atomic valence states. We differentiate three coexisting defect states that differ in their electronic correlation energy and their spatial localization lengths. Their relative abundance is described by a fractional ionicity with covalent and ionic bonding contributions. For Ga₂O₃, our analyses of the resPES data enable us to derive two main aspects: first, experimental access is given to determine the ionicity based on the original concepts of Pauling and Phillips. Second, we report on multi-atomic energy loss processes in the Ga2p core level and X-ray absorption data. The two experimental findings can be explained consistently in the same context of mixed-atomic valence states and intrinsic electronic defects. KW - resonat photoelectron spectroscopy (resPES) KW - X-Ray absorption KW - gallium oxide (Ga₂O₃) KW - intrinsic electronic defects KW - band scheme Y1 - 2018 U6 - https://doi.org/10.1063/1.5010740 SN - 0021-8979 SN - 1089-7550 VL - 123 IS - 16 SP - 161596-1 EP - 161596-9 ER - TY - GEN A1 - Kot, Małgorzata A1 - Wojciechowski, Konrad A1 - Snaith, Henry J. A1 - Schmeißer, Dieter T1 - Evidence of Nitrogen Contribution to the Electronic Structure of the CH₃NH₃PbI₃ Perovskite T2 - Chemistry - A European Journal N2 - Despite fast development of hybrid perovskite solar cells, there are many fundamental questions related to the perovskite film which remain open. For example, there are contradicting theoretical reports on the role of the or-ganic methylammonium cation (CH₃NH₃+)in the methylam-monium lead triiodide (CH₃NH₃PbI₃)perovskite film. From one side it is reported that the organic cation does not contribute to electronic structure of the CH₃NH₃PbI₃ film. From the other side, valence band maximum fluctuations, dependent on the CH₃NH₃+ rotation, have been theoretically predicted. The resonant X-ray photoelectron spectroscopy results reported here show experimental evidence of nitrogen contribution to the CH₃NH₃PbI₃ electronic structure. Moreover,the observed strong resonances of nitrogen with the I 5s and the Pb 5d-6s levels indicate that the CH₃NH₃PbI₃ valence band is extended up to ~18 eV below the Fermi energy, and therefore one should also consider these shallow core levels while modeling its electronic structure. KW - methylammonium lead triiodide (CH₃NH₃PbI₃) KW - electronic structure KW - perovskite solar cells KW - resonant X-ray photoelectron spectroscopy (resPES) Y1 - 2018 U6 - https://doi.org/10.1002/chem.201705144 SN - 0947-6539 SN - 1521-3765 VL - 24 IS - 14 SP - 3539 EP - 3544 ER - TY - GEN A1 - Janowitz, Christoph A1 - Schmeißer, Dieter T1 - Significance of out-of-plane electronic contributions in Bi-cuprates studied by resonant photoelectron spectroscopy at the Cu2p-edge T2 - Superconductor Science and Technology N2 - In high-temperature superconductors with a layered crystal structure, the copper–oxygen planes are commonly considered to dominate the electronic properties around the Fermi energy. As a consequence, out-of-plane contributions are often neglected in the description of these materials. Here we report on a resonant photoemission study of Pb₀,4Bi1,₆Sr₂,₀CaCu₂0₈ ((Pb, Bi)-2212) and Pb₀,₆Bi₁,₄Sr₁.5La₀.5Cu0₆ ((Pb, Bi)-2201)) single crystals to unravel the resonant decay mechanisms at the Cu2p absorption edge. We find evidence for a pronounced polarization dependence caused by two different Auger processes for in-plane and out-of-plane orientations. We deduce that the lowest energy valence state—which is involved in the two Auger processes—consists of three-dimensional contributions by admixed out-of-plane Sr, Bi, and 02p states. It also suggests that the doping-induced charge density is dynamic, fluctuating within the Cu–0 plane, and spills out perpendicular to it. This suggests that out-of-plane electronic degrees of freedom should be included in future consistent theoretical models of these materials. KW - synchrotron radiation KW - polarization dependence KW - 3D hole doping KW - superconductor Y1 - 2018 U6 - https://doi.org/10.1088/1361-6668/aaadf6 SN - 0953-2048 SN - 1361-6668 VL - 31 IS - 4 ER - TY - CHAP A1 - Garain, Samiran A1 - Henkel, Karsten A1 - Mandal, Dipankar A1 - Schmeißer, Dieter T1 - One-Pot Synthesis of Copper Oxide Nanowires and PVDF/CuO Composite Films for Piezoelectric Energy Harvesting Application T2 - Verhandlungen der Deutschen Physikalischen Gesellschaft, Reihe 6, Band 53,3 N2 - Copper oxide (CuO) is an attractive p-type oxide semiconductor with narrow band gap that has intriguing properties such as non-toxicity, chemical stability, electrocatalytic activity, abundant availability and low production cost. Polymeric materials have attracted great interest owing to their high flexibility, light weight, low cost production and high resistance against corrosion. Poly(vinylidene fluoride) (PVDF) is a commonly used piezoelectric polymer due to its excellent flexibility and piezoelectric properties. In this work, we adopted a one-pot synthesis of CuO nanowires by facile and selective chemical etching process of Cu substrate. XPS, XRD, SEM data ascribed the formation of polycrystalline CuO nanowires over the entire Cu surface. It has been observed that the uniformity, shape and size of the nanowires could be conveniently controlled by etching time and etchant concentration. We have also prepared piezoelectric nanogenerator based on the flexible PVDF/CuO composite film, where the traditional electrical poling treatment was avoided. In addition, dielectric properties have been studied to demonstrate the role of interfacial polarization. KW - PVDF KW - electroactive phase KW - nanogenerators KW - energy storage Y1 - 2018 UR - https://www.dpg-verhandlungen.de/year/2018/conference/berlin/part/cpp/session/20/contribution/21 SN - 0420-0195 SP - S. 135 PB - Deutsche Physikalische Gesellschaft CY - Bad Honnef ER - TY - CHAP A1 - Kot, Małgorzata A1 - Naumann, Franziska A1 - Garain, Samiran A1 - Poźarowska, Emilia A1 - Gargouri, Hassan A1 - Henkel, Karsten A1 - Schmeißer, Dieter T1 - Aluminum nitride films prepared by plasma atomic layer deposition using different plasma sources T2 - Verhandlungen der Deutschen Physikalischen Gesellschaft, Reihe 6, Band 53,3 N2 - Aluminum nitride (AlN) thin films are promising for versatile applications in optoelectronics, electronics, piezoelectrics, and acoustics due to their remarkable properties such as wide band gap, high dielectric constant, low electrical conductivity, good piezoelectric coefficient and high ultrasonic velocity. We present a comparative study of AlN films grown by plasma-enhanced atomic layer deposition at 350°C silicon wafers in the SENTECH SI ALD LL system using TMA and NH3 where either a capacitively coupled plasma (CCP) or a direct PTSA (planar triple spiral antenna) source was applied. The films were characterized by ellipsometry, XPS and electrical measurements. The layer properties are discussed concerning the varied ALD process parameters. In general, the process using the direct PTSA source delivered films with higher refractive index and better homogeneity over the wafer achieving also higher growth rates per cycle (GPC) in reduced total cycle durations. Films with refractive index in the range of 2.05 and permittivity around 8 could be realized with a GPC of 1.54 Å/cycle. KW - Aluminium nitride KW - plasma-enhanced atomic layer deposition (PEALD) KW - ellispsometry KW - field emission scanning electron microscopy KW - atomic force microscopy KW - X-ray photoelectron spectroscopy KW - electrical characterization Y1 - 2018 SN - 0420-0195 SP - S. 170 PB - Deutsche Physikalische Gesellschaft CY - Bad Honnef ER - TY - CHAP A1 - Kot, Małgorzata A1 - Kegelmann, Lukas A1 - Kus, Peter A1 - Tsud, Nataliya A1 - Matolínová, Iva A1 - Albrecht, Steve A1 - Matolin, Vladimir A1 - Schmeißer, Dieter T1 - Room temperature atomic layer deposition for perovskite solar cells T2 - Verhandlungen der Deutschen Physikalischen Gesellschaft, Reihe 6, Band 53,3 N2 - After few years of efficiency driven research on perovskite solar cells, the focus now is shifting to understand the underlying processes governing the high efficiency and also to obtain long-term stable devices. Among various deposition methods, atomic layer deposition (ALD) may represent one of the best options, being possible to coat substrates in a very efficient way and at very low temperatures. In our previous work [1] we reported that the efficiency of the solar cell containing aged perovskite film can be enhanced twice while covering the perovskite with a thin ALD alumina film at room temperature. In this work, the chemical, electronic and morphological properties of the fresh perovskite film treated by ALD pulses of the trimethylaluminium and water at room temperature investigated using X-ray Photoelectron Spectroscopy and Field Emission Scanning Electron Microscopy will be discused and correlated with the solar cells performance and stability. [1] M. Kot et al., ChemSusChem 2016, 9, 3401. KW - Perovskite solar cells KW - atomic layer deposition KW - X-Ray photoelectron spectroscopy (XPS) KW - atomic force microscopy KW - field emission scanning electron microscopy KW - photo-conversion efficiency Y1 - 2018 SN - 0420-0195 SP - S. 174 PB - Deutsche Physikalische Gesellschaft CY - Bad Honnef ER - TY - GEN A1 - Garain, Samiran A1 - Sen, Shrabanee A1 - Henkel, Karsten A1 - Schmeißer, Dieter A1 - Mandal, Dipankar T1 - Enhancement of Electroactive β-phase and Superior Dielectric Properties in Cerium Based Poly(vinylidene fluoride) Composite Films T2 - Materials Today: proceedings N2 - In this work we report on the preparation of poly(vinylidene fluoride) (PVDF) films with various mass fractions (wt%) of hydrated rare earth metal salt [(NH4)4Ce(SO4)4.2H2O] (CAS) and its electroactive phase (β- and γ-phase) formation. It was found that CAS can yield high amount of electroactive phases in PVDF. Compared to the neat PVDF film, a significantly increment of dielectric constant (ε ∼ 41) and a low loss factor (tan δ ∼ 0.8) were observed in the PVDF-CAS composite films. Thus the PVDF-CAS composite films with high electroactive phase and superior dielectric properties may meet the requirements of next generation electronic components. KW - PVDF KW - High amount of electroactive phase KW - Superior dielectric properties Y1 - 2018 U6 - https://doi.org/10.1016/j.matpr.2017.11.003 SN - 2214-7853 VL - 5 IS - 3 part 3 SP - 10084 EP - 10090 ER - TY - CHAP A1 - Henkel, Karsten A1 - Kot, Małgorzata A1 - Richter, Matthias A1 - Tallarida, Massimo A1 - Schmeißer, Dieter ED - Wandelt, Klaus T1 - An (In Situ)² Approach: ALD and resPES Applied to Al₂O₃, HfO₂, and TiO₂ Ultrathin Films T2 - Encyclopedia of Interfacial Chemistry: Surface Science and Electrochemistry, Vol. 3.1 N2 - Oxide surface coatings are of importance in tailoring interface properties with respect to surface passivation, adjustment of surface potentials, or providing active centers for surface reactions. In this contribution, we report about surface coatings prepared by the atomic layer deposition (ALD) method. ALD is known for its conformal growth of ultrathin, dense films which exhibit a low concentration of pinholes. KW - Atomic layer deposition (ALD) KW - Resonant photoelectron spectroscopy (resPES) KW - Band scheme KW - Partial density of states (pDOS) KW - Intrinsic charges KW - Intrinsic defects KW - Aluminum oxide (Al₂O₃) KW - Hafnium oxide (HfO₂) KW - Titanium oxide(TiO₂) Y1 - 2018 SN - 978-0-12-809739-7 SN - 978-0-12-809894-3 U6 - https://doi.org/10.1016/B978-0-12-409547-2.13852-1 SP - 18 EP - 26 PB - Elsevier CY - Oxford ER - TY - CHAP A1 - Schmeißer, Dieter A1 - Kot, Małgorzata A1 - Corrêa, Silma Alberton A1 - Das, Chittaranjan A1 - Henkel, Karsten ED - Wandelt, Klaus T1 - Interface Potentials, Intrinsic Defects, and Passivation Mechanisms in Al₂O₃, HfO₂, and TiO₂ Ultrathin Films T2 - Encyclopedia of Interfacial Chemistry: Surface Science and Electrochemistry, vol. 3.1 N2 - We study the electronic structure of ultrathin Al₂O₃, HfO₂, and TiO₂ ALD films by resonant photoelectron spectroscopy. We identify intrinsic defects which are responsible for the active sites in interface reactions, for the incorporation of intrinsic charges, and for the formation of local dipole momenta. All of these features determine the surface potentials and the reactivity of the surface of the atomic layer deposition coated systems. We give examples of charges and dipoles in Al₂O₃, on a study of the surface potentials in HfO₂, and relate the intrinsic defects in TiO₂ to their electrochemical relevance. KW - Atomic layer deposition (ALD) KW - Resonant photoelectron spectroscopy (resPES) KW - Band scheme KW - Interface potential KW - Intrinsic charges KW - Intrinsic defects KW - Partial density of states (pDOS) KW - Exciton KW - Polaron KW - Ligand-to-metal charge transfer KW - Aluminium oxide (Al₂O₃) KW - Hafnium oxide (HfO₂) KW - Titanium Oxide (TiO₂) Y1 - 2018 SN - 978-0-12-809739-7 SN - 978-0-12-814984-3 U6 - https://doi.org/10.1016/B978-0-12-409547-2.14119-8 SP - 162 EP - 171 PB - Elsevier CY - Oxford ER - TY - GEN A1 - Schmeißer, Dieter A1 - Henkel, Karsten A1 - Janowitz, Christoph T1 - Ionicity of ZnO - a key system for transparent conductive oxides T2 - epl : a letters journal exploring the frontiers of physics N2 - The electronic structure of ZnO is dominated by coexisting electron and ionic states/bonds caused by charge polarization and self-trapping phenomena of the valence charges. Their interplay manifests itself in intrinsic electronic defects which have different degree of spatial localization and electronic correlation. The relative abundance of intrinsic defects can be determined by the ionicity factor fi and its value can be derived from three independent experimental procedures in a consistent way. This approach also explains the complex satellite features in the XPS and XAS data. Ionicity and satellite formation are two experimental findings which can be explained consistently in the same context of mixed-atomic valence states and intrinsic electronic defects. KW - Ionicity KW - zinc oxide (ZnO) KW - resonant photoelectron spectroscopy KW - defect states KW - transparent conductive oxide (TCO) Y1 - 2018 U6 - https://doi.org/10.1209/0295-5075/123/27003 SN - 1286-4854 SN - 0295-5075 VL - 123 IS - 2 SP - 27003-p1 EP - 27003-p7 ER - TY - GEN A1 - Kot, Małgorzata A1 - Kegelmann, Lukas A1 - Das, Chittaranjan A1 - Kus, Peter A1 - Tsud, Nataliya A1 - Matolínová, Iva A1 - Albrecht, Steve A1 - Matolin, Vladimir A1 - Schmeißer, Dieter T1 - Room temperature atomic layer deposited Al₂O₃ improves perovskite solar cells efficiency over time T2 - ChemSusChem N2 - Electrical characterisation of perovskite solar cells consisting of room-temperature atomic-layer-deposited aluminium oxide (RT-ALD-Al₂O₃) film on top of a methyl ammonium lead triiodide (CH₃NH₃PbI₃) absorber showed excellent stability of the power conversion efficiency (PCE) over along time. Under the same environmental conditions (for 355 d), the average PCE of solar cells without the ALD layer decreased from 13.6 to 9.6 %, whereas that of solar cells containing 9 ALD cycles of depositing RT-ALD-Al₂O₃on top of CH₃NH₃PbI₃ increased from 9.4 to 10.8 %. Spectromicroscopic investigations of the ALD/perovskite interface revealed that the maximum PCE with the ALD layer is obtained when the so-called perovskite cleaning process induced by ALD precursors is complete. The PCE enhancement over time is probably related to a self-healing process induced by the RT-ALD-Al₂O₃ film. This work may provide a new direction for further improving the long-term stability and performance of perovskite solar cells. KW - Perovskite Solar Cells (PSCs) KW - Atomic layer deposition (ALD) KW - long time stabilty KW - X-Ray photoelectron spectroscopy (XPS) KW - Field-emission scanning electron microscopy (FESEM) Y1 - 2018 U6 - https://doi.org/10.1002/cssc.201801434 SN - 1864-5631 SN - 1864-564X VL - 11 IS - 20 SP - 3640 EP - 3648 ER - TY - CHAP A1 - Henkel, Karsten A1 - Haeberle, Jörg A1 - Müller, Klaus A1 - Janowitz, Christoph A1 - Schmeißer, Dieter ED - Fornari, Robert T1 - Preparation, properties and electronic structure of SnO₂ T2 - Single Crystals of Electronic Materials N2 - This chapter reports about tin oxide (SnO₂), a material which belongs to the transparent conducting oxide family and is best characterized by its high conductivity, high carrier mobility, and the ability to form p-type conductivity. We correlate these properties in terms of localized intrinsic electronic defect states which are resolved by resonant photoelectron spectroscopy measurements. We describe SnO₂ in terms of an inhomogeneous, mixed-ionic-covalent semiconductor in which these intrinsic electronic defects state are stabilized. KW - electronic structure KW - tin oxide (SnO₂) KW - resonant photoelectron spectroscopy KW - intrinsic defect states Y1 - 2018 SN - 978-0-08-102096-8 SN - 978-0-08-102097-5 SP - 547 EP - 572 PB - Elsevier, Woodhead Publishing CY - Duxford ER - TY - GEN A1 - Maity, Kuntal A1 - Garain, Samiran A1 - Henkel, Karsten A1 - Schmeißer, Dieter A1 - Mandal, Dipankar T1 - Natural Sugar-Assisted, Chemically Reinforced, Highly Durable Piezoorganic Nanogenerator with Superior Power Density for Self-Powered Wearable Electronics T2 - ACS Applied Materials & Interfaces N2 - Natural piezoelectric materials are of increasing interest, particularly for applications in biocompatible, implantable, and flexible electronic devices. In this paper, we introduce a cost-effective, easily available natural piezoelectric material, that is, sugar in the field of wearable piezoelectric nanogenerators (PNGs) where low electrical output, biocompatibility, and performance durability are still critical issues. We report on a high-performance piezoorganic nanogenerator (PONG) based on the hybridization of sugar-encapsulated polyvinylidenefluoride (PVDF) nanofiber webs (SGNFW). We explore the crucial role of single-crystal sugar having a fascinating structure along with the synergistic enhancement of piezoelectricity during nanoconfinement of sugar-interfaced macromolecular PVDF chains. As a consequence, the SGNFW-based PONG exhibits outstanding electricity generation capability (e.g.,∼100 V under 10 kPa human finger impact and maximum power density of 33 mW/m2) in combination with sensitivity to abundantly available different mechanical sources (such as wind flow, vibration, personal electronics, and acoustic vibration). Consequently, it opens up suitability in multifunctional self-powered wearable sensor designs for realistic implementation. In addition, commercially available capacitors are charged up effectively by the PONG because of its rapid energy storage capability. The high performance of the PONG not only offers“battery-free”energy generation (several portable units of light-emitting diodes and a liquid crystal display screen are powered up without using external storage) but also promises its use in wireless signal transmitting systems, which widens the potential in personal health care monitoring. Furthermore, owing to the geometrical stress confinement effect, the PONG is proven to be a highly durable power-generating device validated by stability test over 10 weeks. Therefore, the organic nanogenerator would be a convenient solution for portable personal electronic devices that are expected to operate in a self-powered manner. KW - natural piezoelectric material KW - sugar KW - PVDF KW - organic piezoelectric nanogenerator KW - high performance and durability KW - self-powered electronics Y1 - 2018 U6 - https://doi.org/10.1021/acsami.8b15320 SN - 1944-8244 SN - 1944-8252 VL - 10 SP - 44018 EP - 44032 ER - TY - GEN A1 - Biswas, Anirban A1 - Garain, Samiran A1 - Maity, Kuntal A1 - Henkel, Karsten A1 - Schmeißer, Dieter A1 - Mandal, Dipankar T1 - Influence of In situ Synthesized Bismuth Oxide Nanostructures in Self-poled PVDF-based Nanogenerator for Mechanical Energy Harvesting Application T2 - Polymer Composites N2 - A self-poled piezoelectric nanogenerator (NG) based on bismuth oxide (Bi2O3) nanostructures (BNS)-doped poly(vinylidene fluoride) (PVDF) is demonstrated. The in-situ formation of BNS incorporated in the PVDF matrix is realized through a simple solution casting technique that favors the nucleation and stabilization of 99.6% of the electroactive phase in PVDF (i.e., beta/gamma-phases). The enhancement of the output voltage (3.6 V) and current (2.4mA) of the NG based on a nonelectrically poled BNS containing PVDF composite film is achieved and demonstrated by simple repeated human finger imparting. The improvement of the output performance is influenced by the generation of the electroactive polar beta-phase in PVDF, due to the electrostatic interactions between the –CH2–/–CF2– dipoles of PVDF and the surface charge of the BNS. The NGs are able to charge up capacitors demonstrating that the power generation from such a hybrid device structure can be utilized for powering various portable devices. KW - Nanogenerators KW - energy harvesting KW - PVDF KW - bismuth oxide KW - Field-emission scanning electron microscopy (FESEM) KW - X-ray photoelectron spectroscopy (XPS) KW - X-ray diffraction (XRD) KW - Fourier Transform Infrared Spectroscopy (FTIR) Y1 - 2019 U6 - https://doi.org/10.1002/pc.24628 SN - 0272-8397 SN - 1548-0569 VL - 40 IS - S1 SP - E265 EP - E274 ER - TY - GEN A1 - Kot, Małgorzata A1 - Henkel, Karsten A1 - Naumann, Franziska A1 - Gargouri, Hassan A1 - Tarnawska, Lidia Lupina A1 - Wilker, Viola A1 - Kus, Peter A1 - Pożarowska, Emilia A1 - Garain, Samiran A1 - Rouissi, Zied A1 - Schmeißer, Dieter T1 - Comparison of plasma-enhanced atomic layer deposition AlN films prepared with different plasma sources T2 - Journal of Vacuum Science and Technology A N2 - A comparative study of thin aluminum nitride (AlN) films deposited by plasma-enhanced atomic layer deposition in the SENTECH SI ALD LL system applying either a direct inductively coupled plasma (ICP) or an indirect capacitively coupled plasma (CCP) source is presented. The films prepared with the ICP source (based on a planar triple spiral antenna) exhibit improved properties concerning the growth rate per cycle, total cycle duration, homogeneity, refractive index, fixed and mobile electrical charges, and residual oxygen content compared to the CCP source, where the comparison is based on the applied plasma power of 200 W. The increase of the plasma power to 600 W in the ICP process significantly reduces the residual oxygen content and enhances the electrical breakdown field. The AlN layers grown under these conditions, with a growth rate per cycle of 1.54 Å/cycle, contain residual oxygen and carbon concentrations of about 10% and 4%, respectively, and possess a refractive index of 2.07 (at 632.8 nm). KW - Plamsa-enhanced atomic layer deposition (PEALD) KW - inductively coupled KW - capacitively coupled KW - plamsa source KW - ellipsometry KW - X-ray photoelectron spectroscopy (XPS) KW - X-ray diffraction (XRD) KW - Field emission scanning electron microscopy (FESEM) KW - capacitance-voltage (CV) KW - atomic force microscopy Y1 - 2019 U6 - https://doi.org/10.1116/1.5079628 SN - 0734-2101 SN - 1520-8559 VL - 37 IS - 2 ER - TY - GEN A1 - Kotwica, Tomasz A1 - Domaradzki, Jarosław A1 - Wojcieszak, Damian A1 - Sikora, Andrzej A1 - Kot, Małgorzata A1 - Schmeißer, Dieter T1 - Analysis of surface properties of Ti-Cu-Ox gradient thin films using AFM and XPS investigations T2 - Materials Science-Poland N2 - The paper presents results of investigations on surface properties of transparent semiconducting thin films based on (Ti-Cu)oxide system prepared using multi-magnetron sputtering system. The thin films were prepared using two programmed profiles of pulse widt hmodulation coefficient, so called V- and U-shape profiles. The applied powering profiles allowed fabrication of thin films with gradient distribution of Ti and Cu elements over the thickness of deposited layers. Optical investigations allowed determination of transparency of prepared films that reached up to 60 % in the visible part of optical radiation, which makes them attractive for the transparent electronics domain. Surface properties investigations showed that the surface of mixed (Ti-Cu)oxides was sensitive to adsorption, in particular to carbon dioxide and water vapor. Soft etching with argon ions resulted in surface cleaning from residuals, however, deoxidation of Cu-oxide components was also observed. KW - surface KW - gradient distribution KW - thin film oxide Y1 - 2019 U6 - https://doi.org/10.2478/msp-2018-0100 SN - 0137-1339 SN - 2083-1331 SN - 2083-134X VL - 36 IS - 4 SP - 761 EP - 768 ER - TY - GEN A1 - Janowitz, Christoph A1 - Schmeißer, Dieter T1 - Out-of-plane electronic contributions in Bi-cuprates studied by resonant photoelectron spectroscopy at the Cu 2p edge T2 - Verhandlungen der DPG N2 - In high-temperature superconductors with a layered crystal structure out-of-plane contributions are often neglected, while the copper-oxygen planes are commonly considered to dominate the electronic properties around the Fermi energy. Here we report on a resonant photoemission study of (Pb,Bi)2201 and (Pb,Bi)2212 single crystals to unravel the resonant decay mechanisms at the Cu 2p absorption edge. We demonstrate a pronounced polarization dependence caused by two different Auger processes for in-plane and out-of-plane orientations. We deduce that the lowest energy valence state being involved in the two Auger processes, consists of three-dimensional contributions by admixed out-of-plane Sr, Bi, and O 2p states. It also suggests that the doping-induced charge density is dynamic, fluctuating within the Cu-O plane, and spills out perpendicular to it. C. Janowitz and D. Schmeißer, Supercond. Sci. Technol. 31, 045006 (2018) KW - high-temperature superconductors KW - resonant photoemission spectroscopy KW - single crystal KW - doping-induced charge density Y1 - 2019 UR - https://www.dpg-verhandlungen.de/year/2019/conference/regensburg/part/tt/session/49/contribution/19 SN - 0420-0195 SP - 403 EP - 403 PB - Deutsche Physikalische Gesellschaft CY - Bad Honnef ER -