TY - GEN A1 - Kolanek, Krzysztof A1 - Tallarida, Massimo A1 - Schmeißer, Dieter T1 - Height distribution of atomic force microscopy images as a tool for atomic layer deposition characterization T2 - Journal of Vacuum Science and Technology : A N2 - The authors propose the analysis of surface height histograms as a tool for the atomic layer deposition (ALD) growth characterization in the initial stage of the process. ALD of HfO2 on a Si(100)/SiO2 substrate was investigated in situ by ultra high vacuum atomic force microscope working in noncontact mode. The ALD cycles, made by using tetrakis-di-methyl-amido-Hf and H2O as precursors, were performed at 230 C. After each ALD cycle, the relation between the film growth and the root mean square surface roughness was studied. Parameters equivalent to HfO2 layer thickness, coverage, and surface roughness of the substrate and deposited material can be calculated in the proposed routine. KW - Atomic layer deposition (ALD) KW - Atomic force microscopy KW - HfO2 KW - height distribution Y1 - 2013 U6 - https://doi.org/10.1116/1.4754557 VL - 31 IS - 1 SP - 01A104-1 EP - 01A104-9 ER - TY - GEN A1 - Tallarida, Massimo A1 - Schmeißer, Dieter T1 - In situALD experiments with synchrotron radiation photoelectron spectroscopy T2 - Semiconductor Science and Technology N2 - In this contribution, we describe some features of atomic layer deposition (ALD) investigated by means of synchrotron radiation photoelemission spectroscopy (SR-PES). In particular, we show how the surface sensitivity of SR-PES combined with the in situ nature of our investigations can point out interactions between the substrate and ALD precursors. We observed changes on all substrates investigated, included Si, GaAs, Ru and their surface oxides. These interactions are extremely important during the first ALD cycles and induce modifications in the substrate, which might lead to its functionality enhancement. KW - Atomic layer deposition (ALD) KW - in situ KW - photoelectron spectroscopy Y1 - 2012 U6 - https://doi.org/10.1088/0268-1242/27/7/074010 SN - 1361-6641 VL - 27 IS - 7 SP - 074010 ER - TY - GEN A1 - Kukli, Kaupo A1 - Kemell, Marianna A1 - Puukilainen, Esa A1 - Aarik, Jaan A1 - Aidla, Aleks A1 - Sajavaara, Timo A1 - Laitinen, Mikko A1 - Tallarida, Massimo A1 - Sundqvist, Jonas A1 - Ritala, Mikko A1 - Leskelä, Markku T1 - Atomic Layer Deposition of Ruthenium Films from (Ethylcyclopentadienyl)(pyrrolyl)ruthenium and Oxygen T2 - Journal of the Electrochemical Society N2 - Ru films were grown by atomic layer deposition in the temperature range of 275-350 degrees C using (ethylcyclopentadienyl)(pyrrolyl)ruthenium and air or oxygen as precursors on HF-etched Si, SiO(2), ZrO(2), and TiN substrates. Conformal growth was examined on three-dimensional silicon substrates with 20: 1 aspect ratio. ZrO(2) promoted the nucleation of Ru most efficiently compared to other substrates, but the films roughened quickly on ZrO(2) with increasing film thickness. The minimum number of cycles required to form continuous and conductive metal layers could be decreased by increasing the length of the oxygen pulse. In order to obtain well-conducting Ru films growth to thicknesses of at least 8-10 nm on any surface was necessary. Resistivities in the ranges of 30-60 and 14-16 mu Omega . cm were achieved for 4-6 and 10-15 nm thick films, respectively. Delamination became an issue in the Ru films grown to thicknesses about 10 nm and higher. KW - Atomic layer deposition (ALD) KW - Ruthenium Y1 - 2011 U6 - https://doi.org/10.1149/1.3533387 SN - 0013-4651 VL - 158 IS - 3 SP - D158 EP - D165 ER - TY - GEN A1 - Henkel, Karsten A1 - Gargouri, Hassan A1 - Gruska, Bernd A1 - Arens, Michael A1 - Tallarida, Massimo A1 - Schmeißer, Dieter T1 - Capacitance and conductance versus voltage characterization of Al2O3 layers prepared by PE-ALD at 25°C ≤ T ≤ 200°C T2 - Journal of Vacuum Science and Technology A N2 - In this work, plasma enhanced atomic layer deposited (PE-ALD) samples were prepared at substrate temperatures in the range between room temperature (RT) and 200 °C and investigated by capacitance–voltage and conductance–voltage recordings. The measurements are compared to standard thermal atomic layer deposition (T-ALD) at 200 °C. Very low interface state density (D it) ~1011 eV−1 cm−2 could be achieved for the PE-ALD process at 200 °C substrate temperature after postdeposition anneal (PDA) in forming gas at 450 °C. The PDA works very effectively for both the PE-ALD and T-ALD at 200 °C substrate temperature delivering also similar values of negative fixed charge density (N fix) around −2.5 × 1012 cm−2. At the substrate temperature of 150 °C, highest N fix (−2.9 × 1012 cm−2) and moderate D it (2.7 × 1011 eV−1 cm−2) values were observed. The as deposited PE-ALD layer at RT shows both low D it in the range of (1 to 3) × 1011 eV−1 cm−2 and low N fix (−4.4 × 1011 cm−2) at the same time. The dependencies of N fix, D it, and relative permittivity on the substrate temperatures and its adjustability are discussed. KW - Atomic layer deposition (ALD) KW - Al2O3 KW - dielectric properties KW - interface state density KW - fixed oxide charge KW - permittivity Y1 - 2014 UR - http://link.aip.org/link/?JVA/32/01A107&aemail=author U6 - https://doi.org/10.1116/1.4831897 VL - 1 IS - 32 SP - 01A107-1 EP - 01A107-10 ER - TY - THES A1 - Das, Chittaranjan T1 - Spectroscopic and electrochemical study of TiO2/Si photocathode N2 - This thesis focuses on the deposition of thin TiO2 films on p-type Si using atomic layer deposition (ALD) technique, on the study of the electronic proprieties of the grown films and on the electrochemical characterization of TiO2/Si photoelectrodes. The deposition parameters, electronic properties and electrochemical performance and stability of the TiO2/Si samples are correlated. The ALD technique is used to deposit TiO2 with two different precursors namely Titanium isopropoxide and Titanium methoxide onto Si substrates. Laboratory as well as synchrotron based X-ray spectroscopy techniques are used to characterize these films. The growth quality of the TiO2 ALD films is determined by analyzing X-Ray photoelectron spectroscopy (XPS) data in terms of stoichiometry, defect states and Ti3+:Ti4+ ratios. The ALD technique was modified with different heating arrangements to obtain various polymorphs of TiO2. The ALD and anatase TiO2 films are characterized using synchrotron radiation to study their electronic properties and these films are compared with single crystal rutile TiO2. X-ray absorption spectroscopy (XAS) and resonant photoelectron spectroscopy (res-PES) measurements are performed with synchrotron radiation. XAS measurements are used to determine the polymorphs as well as the electronic structure of TiO2. Res-PES measurements are conducted at the O1s and Ti2p edges to study multiple hole Auger decay processes and polaronic and charge transfer states as well as to determine the electronic band gap of the TiO2 layers. One of the main findings of this thesis is the determination of the partial density of states (pDOS) of O and Ti in the conduction and valence band. The combination of the pDOS and the band edge positions obtained from res-PES measurements are used to calculate the charge neutrality level of the TiO2 polymorphs. The photoelectrochemical measurements are conducted on bare-Si and TiO2/Si photoelectrodes. The electrochemical performance of these photoelectrodes is studied in electrolytes having pH values ranging from 1 to 13. The deposition of TiO2 on Si enhances the photoelectrochemical performance of the Si photoelectrode. The TiO2 increases the stability of the photoelectrode in all electrochemical media over 12 hours of experimental condition. Moreover, it is also observed that the TiO2/Si photoelectrode is less responsive to the pH value of the electrolyte. The electrochemical findings are explained on the basis of the electronic properties of the TiO2 layer. The electronic band gap obtained from spectroscopic measurement and the photoelectrochemical measurements are used to explain the performance and stability of the TiO2/Si photoelectrodes. The thesis also addresses the stability of Si microstructured photoelectrodes (SiMPs) prepared by an electrochemical method. The stability of the SiMPs deteriorates more rapidly than that one of the planar Si photoelectrode. However, using a protective ALD TiO2 layer on these SiMPs the overall performance is even more enhanced than on the TiO2/planar Si system. KW - Atomic layer deposition (ALD) KW - Photocathodes KW - TiO2 KW - X-Ray absorption spectroscopy (XAS) KW - X-Ray photoelectron spectroscoopy (XPS) Y1 - 2015 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:co1-opus4-36924 UR - https://opus4.kobv.de/opus4-btu/frontdoor/index/index/docId/3692 ER - TY - CHAP A1 - Rouissi, Zied A1 - Tallarida, Massimo A1 - Schmeißer, Dieter T1 - Study of atomic layer deposition with scanning tunneling microscopy T2 - Verhandlungen der Deutschen Physikalischen Gesellschaft N2 - We present a work concerning the study of the initial steps of atomic layer deposition (ALD) with scanning tunneling microscopy (STM). We focus on the role of the substrates which has been often neglected.However, the detailed knowledge of precursor-substrate reactions is important for the understanding of how ALD proceeds. We report on the reaction of the Al-precursor, trimethyl-Al (TMA), on nanostructured surfaces such as Ag nanoclusters and nanostripes prepared by thermal evaporation on HOPG. We characterized the surface before and after one TMA adsorption pulse at room temperature, observing that the morphology of step edges changes after TMA creating a new terraces with a width of 7-10 nm, translated in the direction of the TMA deposition. This shows that, in case of a regular stepped surface, the substrate morphology would keep the same regularity with the translation in a direction privileged by the precursor absorption. KW - Atomic layer deposition (ALD) KW - Scanning tunneling microscopy (STM) KW - Al2O3 Y1 - 2015 SN - 0420-0195 SP - S. 401 PB - Deutsche Physikalische Gesellschaft CY - Bad Honnef ER - TY - THES A1 - Rouissi, Zied T1 - Role of substrate morphology and chemistry in ALD: HfO2 on Si(111)-H terminated surfaces as model N2 - This work presents an approach to investigate fundamental aspects concerning the early stage of the atomic layer deposition (ALD) growth process on stepped surfaces. The first interaction between precursors and surface is strongly important for the ALD growth that it is still far away from the status to be completely understood. For this purpose, a few ALD-cycles with tetrakis(dimethylamido)hafnium (TDMAH) and trimethylaluminum (TMA) as metallic precursors and water (H₂O) as oxidant has been performed in order to study the initial metal oxide film growth on stepped surfaces such as silicon Si(111)-H terminated, highly oriented pyrolytic graphite (HOPG) and silver deposited HOPG (Ag-HOPG). These investigations have been carried out at various substrate temperatures, where scanning tunneling microscopy (STM) has been used systematically to probe the ALD features. This technique is delivering unique knowledge about the locality and the density of nucleation’s sites on the different substrates. The data collected are then subjected to a mathematical model to understand the growth and to determine the effect of the surface morphology and chemistry on the behavior of the nucleation. The in-situ cycle-by-cycle STM investigation of 4 initial ALD cycles of TDMAH and H₂O on Si(111)-H terminated at room temperature (RT) and at 280°C displays two regimes of growth: In Regime I (1st - 2nd cycle) an increase in roughness in the first cycle to 0.2nm and 0.34nm respectively for RT and 280°C with a partial surface coverage of 71% and 54% is observed. In the 2nd cycle, the coverage increased to ~98% and 94% maintaining the same film height of the 1st cycle. A complete layer is formed in this regime. The results are discussed in reference to the Puurunen model. Following this model, the determination of the reaction mechanism in relation to the number of Hf atoms/nm² attached to the surface reveals that two ligands exchanges occur at RT and one ligand exchange at 280°C in the first regime. In addition, the origin of the reaction saturation was determined to be caused by the steric hindrance effect. In this first regime, the growth model is governed by random deposition followed by Mullins diffusion as determined from the universal values found for the roughness dynamic exponents (α, β, 1/z) of the film. N2 - Diese Arbeit beschäftigt sich mit einer Methode, die fundamentalen Aspekte des anfänglichen Schichtwachstums auf gestuften Oberflächen während des Prozesses der Atomlagenabscheidung (ALD) zu untersuchen. Die initiale Wechselwirkung zwischen den Präkursoren und der Oberfläche ist entscheidend für das ALD-Wachstum, wobei diese Wechselwirkung noch nicht komplett verstanden wird. Zu diesem Zweck wurden einige ALD-Zyklen mit Tetrakis(dimethylamido)hafnium (TDMAH) und Trimethylaluminium (TMA) als metallische Präkursoren und Wasser (H₂O) als Oxidant durchgeführt, um das initiale Filmwachstum von Metalloxiden auf gestuften Oberflächen zu untersuchen. Als Oberflächen kamen dabei Wasserstoff-terminiertes Silizium(111), HOPG (HOPG: ‚highly oriented pyrolytic graphite‘) und mit Silber beschichtetes HOPG (Ag-HOPG) zum Einsatz. Diese Untersuchungen wurden an Schichten, die mit verschiedenen Substrattemperaturen gewachsen wurden, durchgeführt, wobei die Methode der Rastertunnelmikroskopie (RTM, englisch STM für ‚scanning tunneling microscopy‘) systematisch angewendet wurde, um die ALD spezifischen Besonderheiten zu erforschen. Diese Technik liefert einzigartige Erkenntnisse über die örtliche Verteilung von Wachstumskeimen und deren Dichte auf verschiedenen Substraten. Die gemessenen Daten wurden anschließend mit einem mathematischen Modell korreliert, um das Wachstum zu verstehen und den Einfluss der Oberflächenmorphologie und –chemie auf das Keimbildungsverhalten zu bestimmen. Die Zyklus für Zyklus durchgeführten in-situ STM-Untersuchungen der ersten 4 ALD-Zyklen von TDMAH und H₂O auf Wasserstoff-terminierten Si(111) bei Raumtemperatur (RT) und 280°C (Substrattemperatur) liefern zwei Wachstumsregimes: Im ersten Regime (I, erster und zweiter ALD-Zyklus) erhöht sich die Oberflächenrauigkeit im ersten Zyklus auf 0,2nm (RT) bzw. 0,34nm (280°C) mit einer partiellen Oberflächenbedeckung von 71% (RT) bzw. 54% (280°C). Nach dem zweiten Zyklus erhöht sich die Oberflächenbedeckung auf 98% (RT) bzw. 94% (280°C), wobei die gleiche Filmdicke wie im ersten Zyklus beibehalten wird. In diesem Regime wird eine komplette Schicht gebildet. Die Ergebnisse wurden auf Basis des Puurunen-Modells diskutiert. Dabei wurde bei der Untersuchung der Reaktionsmechanismen in Abhängigkeit der auf der Oberfläche haftenden Hafnium-Atome (pro nm²) festgestellt, dass im ersten Regime zwei Liganden-Austauschprozesse bei RT und ein Liganden-Austauschprozess bei 280°C stattfinden. Zusätzlich wurde herausgefunden, dass die Reaktionssättigung durch sterische Behinderung determiniert ist. Die Analyse der universellen dynamischen Rauigkeitsexponenten (α, β, 1/z) der Filme führt zum Schluss, dass in diesem ersten Regime das Wachstum durch eine willkürliche Beschichtung gefolgt von der Mullins-Diffusion bestimmt wird. KW - Gestufte Oberfläche KW - Morphologie KW - Rastertunnelmikroskopie (RTM) KW - Wachstumsstatistik KW - Atomlagenabscheidung (ALD) KW - Atomic layer deposition (ALD) KW - Growth statistics KW - Morphology KW - Scanning tunneling microscopy (STM) KW - Stepped surface Y1 - 2017 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:co1-opus4-42418 UR - https://opus4.kobv.de/opus4-btu/frontdoor/index/index/docId/4241 PB - BTU Cottbus-Senftenberg CY - Cottbus 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 - Tschammer, Rudi A1 - Kosto, Yuliia A1 - Morales, Carlos A1 - Schmickler, Marcel A1 - Henkel, Karsten A1 - Devi, Anjana A1 - Flege, Jan Ingo T1 - Atomic layer deposition of cerium oxide monitored by operando ellipsometry and in-situ X-ray photoelectron spectroscopy T2 - Verhandlungen der DPG N2 - Atomic layer deposition (ALD) has been used extensively to grow homogeneous films with excellent coverage and atomic-scale thickness control for a variety of applications. However, remaining challenges include the investigation of novel precursor-oxidant combinations for low-temperature deposition as well as unraveling the complex interplay between substrate and coating for ultrathin films. In this work, we present a detailed investigation of ultrathin cerium oxide films grown using the novel Ce(dpdmg)3 precursor with H2O and O2. Following a surface science-based approach, we have combined operando spectroscopic ellipsometry and in-situ X-ray photoelectron spectroscopy to allow rapid process optimization and determination of the complex relation between oxide stoichiometry, film thickness and ALD growth parameters, revealing a distinct dependence of inital Ce3+ content on the film thickness and choice of oxidant. This offers the possibility of adjusting the oxide properties to application requirements e.g. in gas sensing by choosing a suitable precursor-oxidant combination. KW - Atomic layer deposition (ALD) KW - ceria KW - low-temperature deposition KW - operando spectroscopic ellipsometry KW - in-situ X-ray photoelectron spectroscopy KW - film thickness KW - oxidant choice KW - cerium oxidation state Y1 - 2024 UR - https://www.dpg-verhandlungen.de/year/2024/conference/berlin/part/o/session/49/contribution/4 SN - 0420-0195 PB - Deutsche Physikalische Gesellschaft CY - Bad Honnef ER -