TY - GEN A1 - Alberton Corrêa, Silma A1 - Brizzi, Simone A1 - Schmeißer, Dieter T1 - Spectroscopic investigation of the electronic structure of thin atomic layer deposition HfO2 films T2 - Journal of Vacuum Science & Technology A N2 - The electronic structure of HfO2 thin films is investigated employing resonant photoelectron spectroscopy (resPES). The detailed analysis of the O1s resonance profile enables the determination of the partial density of states for the valence and the conduction bands as well as the electronic band gap to be 6.2 eV. The position of the charge neutrality level is evaluated. Thereby, it is demonstrated that the resPES data are able to combine information both for the valence as well as for the conduction band states. In addition, evidences for intrinsic in-gap states attributed to polaronic and charge transfer states are given. Electronic charges within the atomic layer deposition-HfO2films are identified, pointing out that the amount of charges is essential to determine the accurate position of the surface potentials. KW - resonant photoelectron spectroscopy KW - hafnium oxide KW - atomic layer deposition KW - partial density of states KW - electronic band gap Y1 - 2016 U6 - https://doi.org/10.1116/1.4935338 SN - 0734-2101 SN - 1520-8559 VL - 34 IS - 1 SP - 01A117-1 EP - 01A117-8 ER - TY - GEN A1 - Sowińska, Małgorzata A1 - Henkel, Karsten A1 - Schmeißer, Dieter A1 - Kärkkänen, Irina A1 - Schneidewind, Jessica A1 - Naumann, Franziska A1 - Gruska, Bernd A1 - Gargouri, Hassan T1 - Plasma-enhanced atomic layer deposition of titanium oxynitrides films: A comparative spectroscopic and electrical study T2 - Journal of Vacuum Science and Technology A N2 - The process parameters’ impact of the plasma-enhanced atomic layer deposition (PE-ALD) method on the oxygen to nitrogen (O/N) ratio in titanium oxynitride (TiOxNy) films was studied. Titanium(IV)isopropoxide in combination with NH3 plasma and tetrakis(dimethylamino) titanium by applying N2 plasma processes were investigated. Samples were characterized by the in situ spectroscopic ellipsometry, x-ray photoelectron spectroscopy, and electrical characterization (current–voltage: I-V and capacitance–voltage: C-V) methods. The O/N ratio in the TiOxNy films is found to be very sensitive for their electric properties such as conductivity, dielectric breakdown, and permittivity. Our results indicate that these PE-ALD film properties can be tuned, via the O/N ratio, by the selection of the process parameters and precursor/coreactant combination. KW - plasma enhanced atomic layer deposition KW - titanium oxynitride KW - X-ray photoelectron spectroscopy KW - ellipsometry KW - current-voltage KW - capacitance-voltage Y1 - 2016 U6 - https://doi.org/10.1116/1.4936227 SN - 0734-2101 SN - 1520-8559 IS - 34 SP - 01A127-1 EP - 01A127-9 ER - TY - GEN A1 - Pitthan, E. A1 - dos Reis, R. A1 - Alberton Corrêa, Silma A1 - Schmeißer, Dieter A1 - Boudinov, H. I. A1 - Stedile, F. C. T1 - Influence of CO annealing in metal-oxide-semiconductor capacitors with SiO2 films thermally grown on Si and on SiC T2 - Journal of Applied Physics N2 - Understanding the influence of SiC reaction with CO, a by-product of SiC thermal oxidation, is a key point to elucidate the origin of electrical defects in SiC metal-oxide-semiconductor (MOS) devices. In this work, the effects on electrical, structural, and chemical properties of SiO2/Si and SiO2/SiC structures submitted to CO annealing were investigated. It was observed that long annealing times resulted in the incorporation of carbon from CO in the Si substrate, followed by deterioration of the SiO2/Si interface, and its crystallization as SiC. Besides, this incorporated carbon remained in the Si surface (previous SiO2/Si region) after removal of the silicon dioxide film by HF etching. In the SiC case, an even more defective surface region was observed due to the CO interaction. All MOS capacitors formed using both semiconductor materials presented higher leakage current and generation of positive effective charge after CO annealings. Such results suggest that the negative fixed charge, typically observed in SiO2/SiC structures, is not originated from the interaction of the CO by-product, formed during SiC oxidation, with the SiO2/SiC interfacial region. KW - metal-oxide-semiconductor KW - silicon KW - silicon carbide KW - CO annealing Y1 - 2016 U6 - https://doi.org/10.1063/1.4939836 SN - 0021-8979 SN - 1089-7550 IS - 119 SP - 025307-1 EP - 025307-6 ER - TY - GEN A1 - Schmeißer, Dieter A1 - Haeberle, Jörg T1 - Intrinsic localized gap states in IGZO and its parent single crystalline TCOs T2 - Thin Solid Films N2 - We report on the X-ray absorption data for Indium–Gallium–Zink–Oxide thin films, amorphous ZnO films, amorphous SnOx films, and single crystalline In2O3, Ga2O3, ZnO, and SnO2 data. These absorption data probe the empty conduction band states explicitly. Also they allow for an elemental assignment using resonant excitation to derive the contributions of each metal ion. We find that the lowest states appear right at the Fermi energy and result from configuration interaction induced charge transfer states which we consider as intrinsic gap states. KW - Transparent conducting oxide KW - X-ray photoelectron spectroscopy KW - Resonant photoemission spectroscopy KW - X-ray absorption spectroscopy KW - Electronic band structure KW - Intrinsic localized gap states Y1 - 2016 U6 - https://doi.org/10.1016/j.tsf.2016.02.010 SN - 0040-6090 SN - 1879-2731 IS - 603 SP - 206 EP - 211 ER - TY - GEN A1 - Kramm, Ulrike Ingrid A1 - Zana, Alessandro A1 - Vosch, Tom A1 - Fiechter, Sebastian A1 - Arenz, Matthias A1 - Schmeißer, Dieter T1 - On the structural composition and stability of Fe–N–C catalysts prepared by an intermediate acid leaching T2 - Journal of Solid State Electrochemistry N2 - The development of highly active and stable non-noble metal catalysts (NNMC) for the oxygen reduction reaction (ORR) in proton exchange membrane fuel cells (PEM-FC) becomes of importance in order to enable cost reduction. In this work, we discuss the structural composition as derived from Fe-57Mößbauer spectroscopy and X-ray diffraction, catalytic performance determined by a rotating (ring)disk electrode (RRDE) technique and stability evaluation of our Fe–N–C catalysts prepared by an intermediate acid leaching (IAL). The advantage of this IAL is given by a high density of active sites within the catalyst, as even without sulphur addition, an iron carbide formation and related disintegration of active sites are inhibited. In addition, our accelerated stress tests illustrate better stability of the sulphur-free IAL catalyst in comparison to the sulphur-added one. KW - Non-noblemetal catalysts (NNMC) KW - Fe–N–C KW - oxygen reduction reaction (ORR) KW - PEM fuel cell (PEM-FC) KW - Accelerated stress tests (ASTs) KW - Mößbauer spectroscopy Y1 - 2016 U6 - https://doi.org/10.1007/s10008-015-3060-z SN - 1432-8488 SN - 1433-0768 N1 - 1. ISSN: P 2. ISSN: E VL - 20 IS - 4 SP - 969 EP - 981 ER - TY - GEN A1 - Kraatz, Matthias A1 - Gall, Martin A1 - Zschech, Ehrenfried A1 - Schmeißer, Dieter A1 - Ho, Paul S. T1 - A model for statistical electromigration simulation with dependence on capping layer and Cu microstructure in two dimensions T2 - Computational Materials Science N2 - A model has been developed to simulate electromigration degradation in an interconnect segment in two dimensions using finite differences. The model was deployed on a parallel computer to statistically assess the lifetimes. The simulation takes into account the diffusion paths for electromigration mass transport along the grain boundaries and the capping layer. The microstructure is generated with a Monte Carlo algorithm, using a modified Potts model. Diffusivities along the grain boundaries and the capping layers were applied as multiples of a base diffusivity and were statistically scattered. The simulation results correlate well with electromigration tests. KW - Electromigration KW - Grain growth KW - Computer simulation KW - 2D KW - Copper Interconnects KW - On-chip KW - Statistics KW - Parallel computing Y1 - 2016 U6 - https://doi.org/10.1016/j.commatsci.2016.04.020 SN - 1879-0801 SN - 0927-0256 VL - 120 SP - 29 EP - 35 ER - TY - GEN A1 - Sowinska, Małgorzata A1 - Brizzi, Simone A1 - Das, Chittaranjan A1 - Kärkkänen, Irina A1 - Schneidewind, Jessica A1 - Naumann, Franziska A1 - Gargouri, Hassan A1 - Henkel, Karsten A1 - Schmeißer, Dieter T1 - Analysis of nitrogen species in titanium oxynitride ALD films T2 - Applied Surface Science N2 - Titanium oxynitride films are prepared by plasma enhanced atomic layer deposition method using two different precursors and nitrogen sources. Synchrotron radiation-based X-ray photoelectron spectroscopy and X-ray absorption spectroscopy are used to characterize the nitrogen species incorporated within these films depending on the deposition parameters. It is found that nitrogen atoms in these films are differently bonded. In particular, it can be distinguished between Ti-ON and Ti-N bonding configurations and molecular nitrogen species caused by precursor fragments. KW - titanium oxynitride KW - X-ray photoelectron spectroscopy KW - X-ray absorption spectroscopy KW - ALD process parameters Y1 - 2016 U6 - https://doi.org/10.1016/j.apsusc.2016.02.096 SN - 0169-4332 SN - 1873-5584 VL - 381 SP - 42 EP - 47 ER - TY - GEN A1 - Das, Chittaranjan A1 - Richter, Matthias A1 - Tallarida, Massimo A1 - Schmeißer, Dieter T1 - Electronic properties of atomic layer deposited films, anatase and rutile TiO2 studied by resonant photoemission spectroscopy T2 - Journal of Physics D: Applied Physics N2 - The TiO2 films are prepared by atomic layer deposition (ALD) method using titanium isopropoxide precursors at 250 °C and analyzed using resonant photoemission spectroscopy (resPES). We report on the Ti2p and O1s core levels, on the valence band (VB) spectra and x-ray absorption spectroscopy (XAS) data, and on the resonant photoelectron spectroscopy (resPES) profiles at the O1s and the Ti3p absorption edges. We determine the elemental abundance, the position of the VB maxima, the partial density of states (PDOS) in the VB and in the conduction band (CB) and collect these data in a band scheme. In addition, we analyze the band-gap states as well as the intrinsic states due to polarons and charge-transfer excitations. These states are found to cause multiple Auger decay processes upon resonant excitation. We identify several of these processes and determine their relative contribution to the Auger signal quantitatively. As our resPES data allow a quantitative analysis of these defect states, we determine the relative abundance of the PDOS in the VB and in CB and also the charge neutrality level. The anatase and rutile polymorphs of TiO2 are analyzed in the same way as the TiO2 ALD layer. The electronic properties of the TiO2ALD layer are compared with the anatase and rutile polymorphs of TiO2. In our comparative study, we find that ALD has its own characteristic electronic structure that is distinct from that of anatase and rutile. However, many details of the electronic structure are comparable and we benefit from our spectroscopic data and our careful analysis to find these differences. These can be attributed to a stronger hybridization of the O2p and Ti3d4s states for the ALD films when compared to the anatase and rutile polymorphs. KW - titanium dioxide (TiO2) KW - resonant photoemission spectroscopy (resPES) KW - defect states KW - partial density of states (pDOS) KW - charge neutrality level (CNL) Y1 - 2016 U6 - https://doi.org/10.1088/0022-3727/49/27/275304 SN - 0022-3727 SN - 1361-6463 VL - 49 IS - 27 SP - 275304-1 EP - 275304-17 ER - TY - GEN A1 - Das, Chittaranjan A1 - Kot, Małgorzata A1 - Henkel, Karsten A1 - Schmeißer, Dieter T1 - Engineering of Sub-Nanometer SiOₓ Thickness in Si Photocathodes for Optimized Open Circuit Potential T2 - ChemSusChem N2 - Silicon is one of the most promising materials to be used for tandem-cell water-splitting devices. However, the electrochemical instability of bare Si makes it difficult to be used for stable devices. Besides that, the photovoltage loss in Si, caused by several factors (e.g., metal oxide protection layer and/or SiO₂/Si or catalyst/Si interface), limits its use in these devices. In this work, we present that an optimized open circuit potential (OCP) of Si can be obtained by controlling the SiOₓ thickness in sub-nanometer range. It can be done by means of a simple and cost-effective way using the combination of a wet chemical etching and the low temperature atomic layer deposition (ALD) of TiO₂. We have found that a certain thickness of the native SiOₓ is necessary to prevent further oxidation of the Si photocathode during the ALD growth of TiO₂. Moreover, covering the Si photocathode with an ALD TiO₂ layer enhances its stability. KW - atomic layer deposition KW - open circuit potential KW - Si photocathodes KW - silica KW - stability Y1 - 2016 U6 - https://doi.org/10.1002/cssc.201600777 SN - 1864-5631 SN - 1864-564X VL - 9 IS - 17 SP - 2332 EP - 2336 ER - TY - GEN A1 - Haeberle, Jörg A1 - Machulik, Stephan A1 - Janowitz, Christoph A1 - Manzke, Recardo A1 - Gaspar, Diana A1 - Barquinha, Pedro A1 - Schmeißer, Dieter T1 - Gap states in the electronic structure of SnO2 single crystals and amorphous SnOxthin films T2 - Journal of Applied Physics N2 - The electronic structure of a SnO2 single crystal is determined by employing resonant photoelectron spectroscopy. We determine the core level, valence band, and X-ray absorption (XAS) data and compare these with those of amorphous SnOx thin films. We find similar properties concerning the data of the core levels, the valence band features, and the absorption data at the O1s edge. We find strong signals arising from intrinsic in-gap states and discuss their origin in terms of polaronic and charge-transfer defects. We deduce from the XAS data recorded at the Sn3d edge that the Sn4d10 ground state has contributions of 4d9 and 4d8 states due to configuration interaction. We identify localized electronic states depending on the strength of the 4d-5s5p interaction and of the O2p-to-Sn4d charge-transfer processes, both appear separated from the extended band-like states of the conduction band. For the amorphous SnOx thin films, significant differences are found only in the absorption data at the Sn3d-edge due to a stronger localization of the in-gap states. KW - SnO2 KW - electronic structure KW - gap states KW - resonant photoelectron spectroscopy (resPES) Y1 - 2016 U6 - https://doi.org/10.1063/1.4962313 SN - 0021-8979 SN - 1089-7550 VL - 120 IS - 10 SP - 105101-1 EP - 105101-13 ER - TY - GEN A1 - Garain, Samiran A1 - Barman, Koushik A1 - Sinha, Tridib Kumar A1 - Jasimuddin, Sk A1 - Haeberle, Jörg A1 - Henkel, Karsten A1 - Schmeißer, Dieter A1 - Mandal, Dipankar T1 - Cerium(III) Complex Modified Gold Electrode: An Efficient Electrocatalyst for the Oxygen Evolution Reaction T2 - ACS Applied Materials and Interfaces N2 - Exploring efficient and inexpensive electrocatalysts for the oxidation of water is of great importance for various electrochemical energy storage and conversion technologies. In the present study, a new water-soluble [Ce III(DMF) (HSO4)3] complex was synthesized and characterized by UV−vis, photoluminescence, and high-resolution X-ray photoelectron spectroscopy techniques. Owing to classic 5d →4f transitions, an intense photoluminescence in the UV region was observed from the water-soluble [CeIII(DMF (HSO4)3] complex. A stacking electrode was designed where self-assembled L-cysteine monolayer modified gold was immobilized with the synthesized cerium complex and was characterized by scanning electron microscopy, electrochemical impedance spectroscopy, and cyclic voltam-metry. The resulting electrode, i.e., [CeIII(DMF)(HSO4)3]−L-cysteine-Au stacks shows high electrocatalytic water oxidation behavior at an overpotential of η ≈0.34 V under neutral pH conditions. We also demonstrated a way where the overpotential is possible to decrease upon irradiation of UV light. KW - water oxidation KW - electrocatalyst KW - photoelectrocatalyst KW - photoluminescence KW - Ce(III)-complex KW - L-cysteine KW - gold electrode Y1 - 2016 U6 - https://doi.org/10.1021/acsami.6b05236 SN - 1944-8244 SN - 1944-8252 VL - 8 IS - 33 SP - 21294 EP - 21301 ER - TY - CHAP A1 - Rouissi, Zied A1 - Tallarida, Massimo A1 - Schmeißer, Dieter T1 - HfO2 grow by ALD on Si(111)-H terminated stepped surface T2 - Verhandlungen der Deutschen Physikalischen Gesellschaft N2 - We studied by STM the growth of HfO2 on Si (111)-H stepped surface (miscut by 0.5∘). The steps are aligned in the [11-2] direction. In order to obtain well defined steps and terraces we prepare the sample by chemical etching in 40% Nh4F. In our in-situ study we investigate the ALD growth of HfO2 by TDMAH and H2O [1-2]. We follow for the first four ALD cycles the distribution of the nucleation sites. We also study the influence of the substrate temperature by comparing the growth within the ALD window at 300K and 580K. We observed that at RT the as-grown HfO2 forms stripes which are oriented normal to the step orientations. Further growth starts from the step edges and proceeds towards the terraces. Defects created by the etching processes act as nucleation sites for 3D islands. Based on our STM data we are able to correlate the structural changes on that inert and stepped Si(111)-H surface during ALD with experimental [3] and theoretical [4] results obtained for planar Si(100) surfaces. [1] M. Tallarida et al., Semicond. Sci. Technol. 27, 074010 (2012) [2] K. Kolanek et al., Thin Solid Films 518, 4688 (2010) [3] K. Kolanek et al., J. Vac. Sci. Technol. A 31, 01A104 (2013) [4]L. Riikka et al., J. Appl. Phys.96, 7686 (2004) KW - atomic layer deposition KW - stepped surfaces KW - scanning tunneling micrsocopy KW - HfO2 KW - Si(111) Y1 - 2016 UR - http://www.dpg-verhandlungen.de/year/2016/conference/regensburg/part/o/session/89/contribution/13?lang=en SP - S. 419 PB - Deutsche Physikalische Gesellschaft CY - Bad Honnef ER - TY - CHAP A1 - Rouissi, Zied A1 - Henkel, Karsten A1 - Tallarida, Massimo A1 - Schmeißer, Dieter T1 - ALD growth of Al2O3 on Stepped Surface of HOPG and Ag-HOPG T2 - Verhandlungen der Deutschen Physikalischen Gesellschaft N2 - Atomic Layer Deposition (ALD) is an excellent deposition technique to grow thin film with high homogeneity coverage on ideal surfaces. Here we are interested in the growth properties on non-ideal (stepped, inert) surfaces. Using STM we studied the growth of Al2O3 by ALD on stepped surface of HOPG and silver covered HOPG (Ag-HOPG). The HOPG sample was cleaved to and then cleaned by N2 in vacuum. We obtain regular steps with terrace widths of 50nm - 500nm. Ag was deposited by thermal deposition on the HOPG. The Al2O3 growth at RT was studies after the first, third, and fifth cycle. Silver evaporation leads to step decoration with island of 1nm-7nm. On the terraces we find the formation of 2D domain of Ag chains. The features caused by the individual ALD cycles of Al2O3 depend on the terrace widths of the HOPG substrate. For small terraces (<100nm) we obtain a growth of 2D domains ( 20nm-25nm) on the edge steps and in the middle of the terrace. For large terraces (>100nm) we find agglomeration of the precursors on individual nucleation sites. Here 3D islands are formed with a height of up to 5nm in the fifth ALD cycle. KW - atomic layer deposition KW - Scanning tunneling microscopy (STM) KW - Al2O3 KW - HOPG Y1 - 2016 UR - http://www.dpg-verhandlungen.de/year/2016/conference/regensburg/part/o/session/89/contribution/12?lang=en SP - S. 419 PB - Deutsche Physikalische Gesellschaft CY - Bad Honnef ER - TY - CHAP A1 - Sowinska, Małgorzata A1 - Das, Chittaranjan A1 - Wojciechowski, Konrad A1 - Snaith, Henry J. A1 - Schmeißer, Dieter T1 - XPS study of the ALD growth of Al₂O₃ on the CH₃NH₃PbI₃ T2 - Verhandlungen der Deutschen Physikalischen Gesellschaft N2 - Organic-inorganic lead halide perovskites have emerged as very attractive absorber materials for the fabrication of low cost and high efficiency solar cells, but a delicate nature of these films is one of the main challenges for a successful commercialization. Typically, when exposed to air or moisture, perovskite films degrade within a couple of hours or days. Moreover, the methylammonium lead triiodide (CH₃NH₃PbI₃) perovskite cannot sustain a prolonged annealing at temperatures around 85∘C. In this work, we are investigating stability (upon air and thermal exposure) of a CH₃NH₃PbI₃ perovskite film coated with a thin layer of Al₂O₃ deposited by atomic layer deposition (ALD). In particular, the chemical and electronic changes occurred at the Al₂O₃/CH₃NH₃PbI₃ interface during the first 50 ALD cycles were monitored ex-situ by high-resolution and surface-sensitive synchrotron-based X-ray photoelectron spectroscopy (SR-XPS). The advantage of the ALD as a deposition method is that it can produce extremely dense layers with a very precise thickness control at room temperature. Detailed SR-XPS data analysis and a stability test of the perovskite film with alumina will be presented. KW - atomic layer deposition KW - perovskite solar cells KW - Al₂O₃ KW - X-Ray photoelectron spectroscopy KW - synchrotron Y1 - 2016 UR - http://www.dpg-verhandlungen.de/year/2016/conference/regensburg/part/cpp/session/31/contribution/6?lang=en SP - S. 206 PB - Deutsche Physikalische Gesellschaft CY - Bad Honnef ER - TY - CHAP A1 - Sowinska, Małgorzata A1 - Das, Chittaranjan A1 - Wojciechowski, Konrad A1 - Snaith, Henry J. A1 - Schmeißer, Dieter T1 - Spectroscopic investigation of the nitrogen role in organic-inorganic perovskite films T2 - Verhandlungen der Deutschen Physikalischen Gesellschaft N2 - Over the past few years, a wide range of device architectures employing organic-inorganic metal halide perovskite absorbers has been reported, with efficiencies exceeding 20%. Despite the tremendous progress, a number of key issues must be resolved before the wide-spread com- mercialization will be possible. Some of the primary challenges include lead toxicity, long-term stability, and fast degradation upon exposure to humid atmosphere. Recent computational and experimental studies suggest that hybrid metal-halide perovskites act as an ionic-electronic conductor. The study of vacancy-mediated migration of I−, Pb2+ and CH3NH3− ions and their relative activation energies suggests that migration of halide vacancies, to and from the interfaces in the solar cell during its operation, is the main conduction mechanism. In this work, we are presenting high resolution synchrotron-based spectroscopic study, which indicates that the contribution of nitrogen into the conduction mechanism of methyl ammonium lead iodide-based (CH3NH3PbI3) perovskite films should not be neglected. The N1s core level and resonant X-ray photoelectron spectroscopy at the N1s-egde of the CH3NH3PbI3 films are discussed in detail. KW - perovskite solar cells KW - X-ray photoelectron spectroscopy KW - nitrogen Y1 - 2016 UR - http://www.dpg-verhandlungen.de/year/2016/conference/regensburg/part/cpp/session/11/contribution/7?lang=en SP - S. 150 PB - Deutsche Physikalische Gesellschaft CY - Bad Honnef ER - TY - GEN A1 - Sowinska, Małgorzata A1 - Das, Chittaranjan A1 - Wojciechowski, Konrad A1 - Rouissi, Zied A1 - Snaith, Henry J. A1 - Schmeißer, Dieter T1 - Atomic layer deposition of Al2O3 on CH3NH3PbI3 for enhancement of perovskite solar cells stability T2 - Synchrotron Radiation in Natural Science : Bulletin of the Polish Synchrotron Radiation Society KW - atomic layer deposition KW - perovskite soloar cells KW - X-ray photoelectron spectroscopy (XPS) KW - Atomic foce microscopy (AFM) Y1 - 2016 SN - 1644-7190 VL - 15 IS - 1-2 SP - S. 33 ER - TY - GEN A1 - Schmeißer, Dieter A1 - Janowitz, Christoph T1 - The Cu2p-edge of superconducting BiSrCu-Oxides studed by resonant Photoelectron Spectroscopy T2 - Synchrotron Radiation in Natural Science : Bulletin of the Polish Synchrotron Radiation Society KW - synchrotron raidation KW - superconductor Y1 - 2016 SN - 1644-7190 VL - 15 IS - 1-2 SP - S. 35 ER - TY - CHAP A1 - Das, Chittaranjan A1 - Tallarida, Massimo A1 - Schmeißer, Dieter T1 - TiO2 laminated Silicon microstructures based stable photocathode for water splitting T2 - Verhandlungen der Deutschen Physikalischen Gesellschaft N2 - The photoelectrochemical (PEC) water splitting is one of the most efficient ways to obtain hydrogen from water using solar power which can be used as carbon free fuel. The PEC device can bedesigned using semiconducting material that will convert solar radiation to H2. Silicon can be one of the best choices for PEC due to its success in solar cells technology. There are certain issues with Si such as stability in electrochemical medium [1] and higher surface reflectance (25%) which limits the Si as an ideal candidate for PEC technique [2]. In the present work we addressed these issues by surface structuring and laminating the surface with metal oxide. The microstructuring of Si was done by electrochemical method. The Si microstructure photocathode was stabilized by thin layer of ALD grown TiO2 film. The microstructuring and lamination of Si photocathode by ALD layer of TiO2 decreased the reflectance ofthe surface and shift the onset potential towards anodic direction by 350 mV with a prolonged stability over 60 hours[3]. [1] C. Levy-Clement, J. Electrochem. Soc 1991, 12, 69 [2] J. Oh, et al. Energy Environ. Sci., 2011, 4, 1690 [3] C. Das, et al. Nanoscale 2015,7, 7726 KW - water splitting KW - TiO2 KW - atomic layer deposition (ALD) KW - Si photoelectrodes Y1 - 2016 UR - http://www.dpg-verhandlungen.de/year/2016/conference/regensburg/part/ds/session/48/contribution/4?lang=en SP - S. 213 PB - Deutsche Physikalische Gesellschaft CY - Bad Honnef ER - TY - GEN A1 - Haeberle, Jörg A1 - Brizzi, Simone A1 - Gaspar, Diana A1 - Barquinha, Pedro A1 - Galazka, Zbigniew A1 - Schulz, Detlev A1 - Schmeißer, Dieter T1 - A spectroscopic comparison of IGZO thin film and the parent In2O3, Ga2O3, and ZnO single crystals T2 - Materials Research Express N2 - We use resonant photoelectron spectroscopy at the Zn 2p, Ga 2p, In 3d, and O 1s absorption edges to report on the electronic properties of indium–gallium–zinc-oxide thin films. We also compare the data with the respective data of the corresponding single crystals In2O3, Ga2O3, and ZnO. We focus on the elemental composition and, in particular, find no evidence for oxygen deficiency. The In, Ga, and Zn absorption data at resonance can be used to analyze the conduction band states in detail. We deduce that a configuration interaction between d10s0 and d9s1states is of importance. We provided a novel mechanism in which configuration interaction induced gap states create both, extended unoccupied states around E F as well as localized occupied states within the gap. KW - transparent conducting oxides (TCO) KW - resonant photoelectron spectroscopy KW - in-gapdefect states Y1 - 2016 U6 - https://doi.org/10.1088/2053-1591/3/10/106302 SN - 2053-1591 VL - 3 IS - 10 SP - 106302-1 EP - 106302-17 ER - TY - GEN A1 - Ghosh, Sujoy Kumar A1 - Biswas, Anirban A1 - Sen, Shrabanee A1 - Das, Chittaranjan A1 - Henkel, Karsten A1 - Schmeißer, Dieter A1 - Mandal, Dipankar T1 - Yb3+ Assisted Self-Polarized PVDF Based Ferroelectretic Nanogenerator: A Facile Strategy of Highly Efficient Mechanical Energy Harvester Fabrication T2 - Nano Energy N2 - Ytterbium (Yb3+) assisted porous poly(vinylidene fluoride) (PVDF) composite film comprising flexible ferroelectretic nanogenerator (FTNG) is highlighted where traditional poling treatment is completely avoided. The piezoelectric output of FTNG is realized by the co-operative activity of self-polarized -CH2/-CF2 dipoles with porous electret-like structure in the composite film. Owing to extraordinary ferroelectric and dielectric properties, FTNG is acting as a highly efficient mechanical energy harvester. It is capable to capture several forms of abundant mechanical energy arising from humanfinger movements, machine vibrations and sound waves. As a proof of concept, under compressive deformation, FTNG is enable to instantly powers up several consumer electronics and thus provides a promising strategy for achieving self-powered electronic devices. KW - PVDF KW - Yb 3+ KW - Porous ferroelectret material KW - Self-polarization KW - Ferroelectretic nanogenerator KW - Mechanical energy harvester KW - Self-powered electronics Y1 - 2016 U6 - https://doi.org/10.1016/j.nanoen.2016.10.042 SN - 2211-2855 VL - 2016 IS - 30 SP - 621 EP - 629 ER - TY - GEN A1 - Kot, Małgorzata A1 - Das, Chittaranjan A1 - Wang, Zhiping A1 - Henkel, Karsten A1 - Rouissi, Zied A1 - Wojciechowski, Konrad A1 - Snaith, Henry J. A1 - Schmeißer, Dieter T1 - Room-Temperature Atomic Layer Deposition of Al₂O₃: Impact on Efficiency, Stability and Surface Properties in Perovskite Solar Cells T2 - ChemSusChem N2 - In this work, solar cells with a freshly made CH₃NH₃PbI₃ perovskite film showed a power conversion efficiency (PCE) of 15.4 % whereas the one with 50 days aged perovskite film only 6.1 %. However, when the aged perovskite was covered with a layer of Al₂O₃ deposited by atomic layer deposition (ALD) at room temperature (RT), the PCE value was clearly enhanced. X-ray photoelectron spectroscopy study showed that the ALD precursors are chemically active only at the perovskite surface and passivate it. Moreover, the RT-ALD-Al2O3-covered perovskite films showed enhanced ambient air stability. KW - Al₂O₃ KW - atomic layer deposition (ALD) KW - perovskite KW - solar cells KW - X-ray photoelectron spectroscopy (XPS) Y1 - 2016 U6 - https://doi.org/10.1002/cssc.201601186 SN - 1864-5631 SN - 1864-564X VL - 9 IS - 24 SP - 3401 EP - 3406 ER - TY - GEN A1 - Cuypers, Daniel A1 - Fleischmann, Claudia A1 - Dorp, Dennis H. von A1 - Brizzi, Simone A1 - Tallarida, Massimo A1 - Müller, Matthias A1 - Hönicke, Philipp A1 - Billen, Arne A1 - Chintala, Ravi A1 - Conard, Thierry A1 - Schmeißer, Dieter A1 - Vandervorst, Wilfried A1 - Elshocht, Sven van A1 - Armini, Silvia A1 - De Gendt, Stefan A1 - Adelmann, Christoph T1 - Sacrificial Self-Assembled Monolayers for the Passivation of GaAs(100) Surfaces and Interfaces T2 - Chemistry of Materials N2 - The use of sacrificial self-assembled monolayers (SAMs) to prepare clean n-type GaAs (100) surfaces without band bending in vacuo is demonstrated. GaAs surface passivation using octadecanethiol SAMs after HCl cleaning is shown to lead to an enhancement of the room-temperature photoluminescence intensity. Synchrotron-radiation photoelectron spectroscopy (SRPES) finds that the interfacial oxide between GaAs and the SAM remains below the detection limit. Evidence for both Ga–S and As–S bonds at the GaAs–thiolate interface is found. The limited thermal stability of the SAM allows the desorption of the alkyl chains by in situ thermal annealing at temperatures above 180 °C, leaving S bonded to Ga behind. The resulting surface contains only a very small amount of O (0.05 ML coverage) and C (about 3% of the SAM remaining) and shows no band bending with the surface Fermi level close to the conduction band. Atomic layer deposition of Al₂O₃ on this surface occurs via the formation of Al–S bonds without introducing any additional band bending. This indicates that the surface preparation of n-type GaAs (100) using sacrificial octadecanethiol SAMs followed by in situ thermal removal provides a route toward GaAs/oxide interfaces without interfacial oxides and without band bending. KW - GaAs KW - passivation KW - Al₂O₃ KW - atomic layer deposition (ALD) KW - Synchrotron-radiation photoelectron spectroscopy (SRPES) KW - self assembled monolayers (SAM) KW - interface engineering Y1 - 2016 U6 - https://doi.org/10.1021/acs.chemmater.6b01732 SN - 0897-4756 SN - 1520-5002 VL - 28 IS - 16 SP - 5689 EP - 5701 ER - TY - GEN A1 - Corrêa, Silma Alberton A1 - Brizzi, Simone A1 - Schmeißer, Dieter T1 - Depicting the Electronic Structure of HfO₂ Films by Spectroscopic Techniques T2 - ECS Transactions N2 - The electronic structure of HfO₂ films was investigated. The partial density of states for the valence and the conduction bands was determined by the detailed analysis of the O1s resonance profile by resonant photoelectron spectroscopy. The positions of valence band maximum and conduction band minimum, the excitation range for the polaronic states and the range of charge transfer band were found to be not influenced by the preparation conditions. The band gap was determined to be 6.2 eV and the energy of the charge neutrality level (referred to vacuum level) was determined as 4.7 eV. The Fermi level position was observed to vary about 1.2 eV depending on the preparation conditions, which indicates the presence of charges within the films. KW - HfO₂ KW - resonant photoelectron spectroscopy (resPES) KW - electronic structure KW - partial density of states KW - charge neutrality level Y1 - 2016 U6 - https://doi.org/10.1149/07506.0145ecst SN - 1938-6737 SN - 1938-5862 VL - 75 IS - 6 SP - 145 EP - 153 ER -