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 - 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 - Henkel, Karsten A1 - Das, Chittaranjan A1 - Kot, Małgorzata A1 - Schmeißer, Dieter A1 - Naumann, Franziska A1 - Kärkkänen, Irina A1 - Gargouri, Hassan T1 - In-gap states in titanium dioxide and oxynitride atomic layer deposited films T2 - Journal of Vacuum Science and Technology: A N2 - Valence band (VB) spectra of titanium dioxide (TiO2) and oxynitride (TiOxNy) films prepared by different atomic layer deposition (ALD) processes are compared and related to electrical characterization [current–voltage (JV) and capacitance–voltage (CV)] results. By increasing the nitrogen amount in the TiO2 film, band-gap narrowing is observed. The band-gap decrease is related to the contribution of the nitrogen density of states, which induces defects within the band-gap and thus reduces its optical band-gap. In-gap states are found in the VB spectra at 1 eV below the Fermi energy in all investigated ALD samples, i.e., in TiO2 as well as in TiOxNy films. An exponential correlation between leakage current density and in-gap state intensity is derived by the combination of JV measurements and VB spectra, whereas the in-gap states seem to have no influence on hysteresis and fixed oxide charges found in the CV data. It is argued that the in-gap states in TiO2 and TiOxNy have an excitonic or polaronic origin. Both, band-gap narrowing and in-gap state intensity can be tuned by the ALD process selection and the variation of its parameters. KW - Titanium dioxide (TiO2) KW - Titanium oxynitrdie (TiON) KW - valence band spectra KW - in-gap states KW - band-gap narrowing KW - electrical characterization Y1 - 2017 U6 - https://doi.org/10.1116/1.4972247 SN - 0734-2101 SN - 1520-8559 VL - 35 IS - 1 SP - 01B135-1 EP - 01B135-8 ER - TY - CHAP A1 - Łobaza, Justyna A1 - Kot, Małgorzata A1 - Schmeißer, Dieter T1 - Analysis of surface oxidation of TiON ALD films T2 - Verhandlungen der Deutschen Physikalischen Gesellschaft N2 - Titanium oxynitride (TiON) films are interesting due to their remarkable optical and electronic properties which strongly depend on the O/N ratio. However, it is known that films containing Ti are prone to oxidation in contact with the air [1]. In this work, we study the thickness of a surface oxidation layer which is inherently formed on the atomic layer deposition (ALD) grown TiON/TiN films on Si substrate. We use an Ar+ ion bombardment source and X-ray photoelectron spectroscopy (XPS) for this analysis. We calibrate the sputter rate by using substrate signal intensity decay (here Si 2p) in the XPS spectra of the 5 nm thick TiON sample accordingly. This rate is assumed to be constant when films with a larger thickness are analyzed. We find that the surface oxidation layer is about 1 nm thick, independent on the detailed ALD parameters of the films. The TiN films found underneath are close to the stoichiometric values and have a residual O content below 5%. Finally, we compare these data to our previous results collected with synchrotron-based radiation source [2,3]. References: [1] Sowinska et al., Applied Physics Letters 100, 233509 (2012). [2] M. Sowinska et al., Applied Surface Science 381, 42-47 (2016). [3] M. Sowińska et al., Journal of Vacuum Science and Tech- nology A, 01A12734 (2016). KW - titanium oxynitride KW - X-Rax photoelectron spectroscopy KW - depth profiling KW - sputtering Y1 - 2017 UR - http://www.dpg-verhandlungen.de/year/2017/conference/dresden/part/ds/session/21/contribution/7 SN - 0420-0195 SP - S. 202 PB - Deutsche Physikalische Gesellschaft CY - Bad Honnef ER - TY - CHAP A1 - Kot, Małgorzata A1 - Wojciechowski, Konrad A1 - Snaith, Henry J. A1 - Schmeißer, Dieter T1 - Characterization of the perovskite solar cells containing atomic layer deposited Al2O3 buffer layer T2 - Verhandlungen der Deutschen Physikalischen Gesellschaft e.V. N2 - Hybrid perovskites have potential to overcome performance limits of the current solar cell technologies and achieve low cost and high versatility. Nonetheless, they are prone to degradation in presence of moisture within a couple of hours or days. In this work, we use the atomic layer deposition (ALD) of Al2O3 on the CH3NH3PbI3 perovskite at room temperature in order to verify if this thin ALD layer may protect the perovskite film against moisture degradation and to check the impact of the Al2O3 on the solar to power conversion efficiency (PCE). Depth profiling X-ray photoelectron spectroscopy study shows that the ALD precursors are chemically active only at the perovskite surface and the film bulk is not affected. The perovskite film coated with Al2O3 layer has enhanced moisture stability. Solar cells with a fresh-made CH3NH3PbI3 perovskite film have shown PCE of 15.4%, while the one with 50 days aged perovskite only 6.1%. However, when the aged perovskite is covered with RT-ALD-Al2O3 the PCE value is clearly enhanced.[1] [1] M. Kot et al., Room temperature ALD impact on efficiency, stability and surface properties in perovskite solar cells, ChemSusChem,acctepted. KW - Perovskite solar cell KW - atomic layer deposition KW - Al2O3 KW - efficiency recovery Y1 - 2017 UR - http://www.dpg-verhandlungen.de/year/2017/conference/dresden/part/cpp/session/38/contribution/5 SN - 0420-0195 SP - S. 147 PB - Deutsche Physikalische Gesellschaft CY - Bad Honnef ER - TY - CHAP A1 - Henkel, Karsten A1 - Kot, Małgorzata A1 - Schmeißer, Dieter T1 - Localized defect states and charge trapping in Al₂O₃ films prepared by atomic layer deposition T2 - Verhandlungen der Deutschen Physikalischen Gesellschaft N2 - The evaluation of the electronic structure and intrinsic defect mechanisms in Al₂O₃ thin films is essential for their effective use in applications with desired functionality such as surface passivation schemes for solar cells [1]. We present a comparative study of different Al₂O₃ films grown by atomic layer deposition (ALD) [2]. The layers were deposited on different substrates using the same aluminum precursor (TMA, trimethylalumium) and employing different process parameters (thermal-ALD, plasma-enhanced-ALD, substrate temperature). These films were characterized by resonant photoelectron spectroscopy and by electrical measurements (capacitance-voltage). For all films investigated intrinsic defect states within the electronic band gap were observed including excitonic, polaronic, and charge-transfer defect states, where their relative abundance is subject of the choice of ALD parameters and of the used substrate. The spectroscopic assigned in-gap defect states are related with electronic charges as determined in the electrical measurements. [1] G. Dingemans and W.M.M. Kessels, J. Vac. Sci. Technol. A 30, 040802 (2012). [2] K. Henkel, M. Kot, D. Schmeißer, J. Vac. Sci. Technol. A 35, (2017), accepted. KW - defect states KW - Al₂O₃ KW - resonant photoelectron spectroscopy KW - X-Ray absorption spectroscopy KW - capacitance-voltage measurements Y1 - 2017 UR - http://www.dpg-verhandlungen.de/year/2017/conference/dresden/part/ds/session/32/contribution/4 SN - 0420-0195 SP - S. 205 PB - Deutsche Physikalische Gesellschaft CY - Bad Honnef ER - TY - GEN A1 - 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 - 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 - 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 - Kot, Małgorzata A1 - Wojciechowski, Konrad A1 - Snaith, Henry J. A1 - Schmeißer, Dieter T1 - Evidence of Nitrogen Contribution to the Electronic Structure of the CH₃NH₃PbI₃ Perovskite T2 - Chemistry - A European Journal N2 - Despite fast development of hybrid perovskite solar cells, there are many fundamental questions related to the perovskite film which remain open. For example, there are contradicting theoretical reports on the role of the or-ganic methylammonium cation (CH₃NH₃+)in the methylam-monium lead triiodide (CH₃NH₃PbI₃)perovskite film. From one side it is reported that the organic cation does not contribute to electronic structure of the CH₃NH₃PbI₃ film. From the other side, valence band maximum fluctuations, dependent on the CH₃NH₃+ rotation, have been theoretically predicted. The resonant X-ray photoelectron spectroscopy results reported here show experimental evidence of nitrogen contribution to the CH₃NH₃PbI₃ electronic structure. Moreover,the observed strong resonances of nitrogen with the I 5s and the Pb 5d-6s levels indicate that the CH₃NH₃PbI₃ valence band is extended up to ~18 eV below the Fermi energy, and therefore one should also consider these shallow core levels while modeling its electronic structure. KW - methylammonium lead triiodide (CH₃NH₃PbI₃) KW - electronic structure KW - perovskite solar cells KW - resonant X-ray photoelectron spectroscopy (resPES) Y1 - 2018 U6 - https://doi.org/10.1002/chem.201705144 SN - 0947-6539 SN - 1521-3765 VL - 24 IS - 14 SP - 3539 EP - 3544 ER - TY - CHAP A1 - Kot, Małgorzata A1 - Naumann, Franziska A1 - Garain, Samiran A1 - Poźarowska, Emilia A1 - Gargouri, Hassan A1 - Henkel, Karsten A1 - Schmeißer, Dieter T1 - Aluminum nitride films prepared by plasma atomic layer deposition using different plasma sources T2 - Verhandlungen der Deutschen Physikalischen Gesellschaft, Reihe 6, Band 53,3 N2 - Aluminum nitride (AlN) thin films are promising for versatile applications in optoelectronics, electronics, piezoelectrics, and acoustics due to their remarkable properties such as wide band gap, high dielectric constant, low electrical conductivity, good piezoelectric coefficient and high ultrasonic velocity. We present a comparative study of AlN films grown by plasma-enhanced atomic layer deposition at 350°C silicon wafers in the SENTECH SI ALD LL system using TMA and NH3 where either a capacitively coupled plasma (CCP) or a direct PTSA (planar triple spiral antenna) source was applied. The films were characterized by ellipsometry, XPS and electrical measurements. The layer properties are discussed concerning the varied ALD process parameters. In general, the process using the direct PTSA source delivered films with higher refractive index and better homogeneity over the wafer achieving also higher growth rates per cycle (GPC) in reduced total cycle durations. Films with refractive index in the range of 2.05 and permittivity around 8 could be realized with a GPC of 1.54 Å/cycle. KW - Aluminium nitride KW - plasma-enhanced atomic layer deposition (PEALD) KW - ellispsometry KW - field emission scanning electron microscopy KW - atomic force microscopy KW - X-ray photoelectron spectroscopy KW - electrical characterization Y1 - 2018 SN - 0420-0195 SP - S. 170 PB - Deutsche Physikalische Gesellschaft CY - Bad Honnef ER - TY - CHAP A1 - Kot, Małgorzata A1 - Kegelmann, Lukas A1 - Kus, Peter A1 - Tsud, Nataliya A1 - Matolínová, Iva A1 - Albrecht, Steve A1 - Matolin, Vladimir A1 - Schmeißer, Dieter T1 - Room temperature atomic layer deposition for perovskite solar cells T2 - Verhandlungen der Deutschen Physikalischen Gesellschaft, Reihe 6, Band 53,3 N2 - After few years of efficiency driven research on perovskite solar cells, the focus now is shifting to understand the underlying processes governing the high efficiency and also to obtain long-term stable devices. Among various deposition methods, atomic layer deposition (ALD) may represent one of the best options, being possible to coat substrates in a very efficient way and at very low temperatures. In our previous work [1] we reported that the efficiency of the solar cell containing aged perovskite film can be enhanced twice while covering the perovskite with a thin ALD alumina film at room temperature. In this work, the chemical, electronic and morphological properties of the fresh perovskite film treated by ALD pulses of the trimethylaluminium and water at room temperature investigated using X-ray Photoelectron Spectroscopy and Field Emission Scanning Electron Microscopy will be discused and correlated with the solar cells performance and stability. [1] M. Kot et al., ChemSusChem 2016, 9, 3401. KW - Perovskite solar cells KW - atomic layer deposition KW - X-Ray photoelectron spectroscopy (XPS) KW - atomic force microscopy KW - field emission scanning electron microscopy KW - photo-conversion efficiency Y1 - 2018 SN - 0420-0195 SP - S. 174 PB - Deutsche Physikalische Gesellschaft CY - Bad Honnef ER - TY - CHAP A1 - 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 - Kot, Małgorzata A1 - Kegelmann, Lukas A1 - Das, Chittaranjan A1 - Kus, Peter A1 - Tsud, Nataliya A1 - Matolínová, Iva A1 - Albrecht, Steve A1 - Matolin, Vladimir A1 - Schmeißer, Dieter T1 - Room temperature atomic layer deposited Al₂O₃ improves perovskite solar cells efficiency over time T2 - ChemSusChem N2 - Electrical characterisation of perovskite solar cells consisting of room-temperature atomic-layer-deposited aluminium oxide (RT-ALD-Al₂O₃) film on top of a methyl ammonium lead triiodide (CH₃NH₃PbI₃) absorber showed excellent stability of the power conversion efficiency (PCE) over along time. Under the same environmental conditions (for 355 d), the average PCE of solar cells without the ALD layer decreased from 13.6 to 9.6 %, whereas that of solar cells containing 9 ALD cycles of depositing RT-ALD-Al₂O₃on top of CH₃NH₃PbI₃ increased from 9.4 to 10.8 %. Spectromicroscopic investigations of the ALD/perovskite interface revealed that the maximum PCE with the ALD layer is obtained when the so-called perovskite cleaning process induced by ALD precursors is complete. The PCE enhancement over time is probably related to a self-healing process induced by the RT-ALD-Al₂O₃ film. This work may provide a new direction for further improving the long-term stability and performance of perovskite solar cells. KW - Perovskite Solar Cells (PSCs) KW - Atomic layer deposition (ALD) KW - long time stabilty KW - X-Ray photoelectron spectroscopy (XPS) KW - Field-emission scanning electron microscopy (FESEM) Y1 - 2018 U6 - https://doi.org/10.1002/cssc.201801434 SN - 1864-5631 SN - 1864-564X VL - 11 IS - 20 SP - 3640 EP - 3648 ER - TY - GEN A1 - 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 - Obstarczyk, Agata A1 - Kaczmarek, Danuta A1 - Wojcieszak, Damian A1 - Mazur, Michał A1 - Domaradzki, Jarosław A1 - Kotwica, Tomasz A1 - Pastuszek, Roman A1 - Schmeißer, Dieter A1 - Mazur, Piotr A1 - Kot, Małgorzata T1 - Tailoring optical and electrical properties of thin-film coatings based on mixed Hf and Ti oxides for optoelectronic application T2 - Materials and Design N2 - In this work multi-magnetron sputtering stand was used for the deposition of the mixed oxides thin films based on HfO2 and TiO2. In order to obtain various material composition the power released to each magnetron (containing metallic hafnium and titanium targets) was precisely selected. Structural, surface, optical, electrical and mechanical properties of as-deposited coatings were analyzed. Depending on the hafnium content in the deposited thin films various types of the microstructure was obtained, i.e. HfO2-monoclinic, amorphous and TiO2-rutile. Increase of Ti content above 28 at. % in the as-prepared mixed oxides coatings caused their amorphization. It was found that with an increase of Ti content in prepared coatings their surface roughness and simultaneously water contact angle decreased. Performed measurements of electrical properties revealed that the lowest leakage current density in the range of 10−7 – 10−8 A/cm2 was obtained for amorphous coatings. Moreover, the tailoring of the dielectric constant was possible by a proper selection of material composition and microstructure of the deposited thin films. Average transparency in the visible wavelength region was in the range of ca. 79–86%. The influence of material composition and structure on shifting of the fundamental absorption edge and optical bandgap energy was also observed. The refractive index increased with an increase of Ti content, while extinction coefficient was the lowest for amorphous coatings. Additionally, hardness values were dependent on the material composition and optical packing density and were in the range from 7.6 GPa to 10.1 GPa. KW - Magnetron sputtering KW - Optical coatings KW - Electrical properties KW - Mixed oxides KW - HfO2 KW - TiO2 KW - High-k oxides KW - Amorphous thin films Y1 - 2019 U6 - https://doi.org/10.1016/j.matdes.2019.107822 SN - 0264-1275 VL - 175 ER - TY - GEN A1 - Kot, Małgorzata A1 - Das, Chittaranjan A1 - Baran, Derya A1 - Saliba, Michael T1 - Themed issue on electronic properties and characterisation of perovskites T2 - Journal of Materials Chemistry C KW - perovskite solar cells KW - electronic properties of perovskites Y1 - 2019 U6 - https://doi.org/10.1039/c9tc90085c SN - 2050-7526 SN - 2050-7534 VL - 7 SP - 5224 EP - 5225 ER -