Article
Chemistry, Physical
Makoto Takayanagi, Takashi Tsuchiya, Shigenori Ueda, Tohru Higuchi, Kazuya Terabe
Summary: The combination of in situ HAXPES and electrochemical measurements allows for the separation and quantitative evaluation of reversible Li+, irreversible Li2WO4 formation, and irreversible Li+ trapping. The inserted Li+ conversion ratios of reversible Li+, irreversible Li2WO4 formation, and irreversible Li+ trapping were clarified to be 41.4%, 50.9%, and 7.7%, respectively.
APPLIED SURFACE SCIENCE
(2021)
Article
Chemistry, Physical
K. Ruwisch, T. Pohlmann, M. Hoppe, F. Bertram, P. Shafer, J. Wollschlager, K. Kuepper
Summary: This study investigates the chemical and magnetic properties of thin magnetite/cobalt ferrite bilayers deposited on MgO(001). Different CoxFe3-xO4 stoichiometries in combination with Fe3O4 layers of varying thickness were prepared, and the quality of the films were controlled by various techniques. Enhanced interface magnetization was observed in the bilayers, along with characteristic exchange-spring behavior as shown by superconducting quantum interference device measurements.
JOURNAL OF PHYSICAL CHEMISTRY C
(2021)
Review
Materials Science, Multidisciplinary
Suresh Thapa, Rajendra Paudel, Miles D. Blanchet, Patrick T. Gemperline, Ryan B. Comes
Summary: Emergent behavior at oxide interfaces has driven research in complex oxide films for the past 20 years. Advances in synthesis and X-ray photoelectron spectroscopy (XPS) studies have enabled the growth of interfaces with unique properties not found in bulk materials. The in situ integration of synthesis and spectroscopy has improved the growth process and accelerated scientific discovery, with techniques including determination of interfacial intermixing, valence band alignment, and interfacial charge transfer.
JOURNAL OF MATERIALS RESEARCH
(2021)
Article
Nanoscience & Nanotechnology
Kyle P. Kelley, Vinit Sharma, Wenrui Zhang, Arthur P. Baddorf, Von B. Nascimento, Rama K. Vasudevan
Summary: The study reveals an unprecedented surface reconstruction in La₁-xSrₓMnO₃, indicating its potential for applications and the ability to tune surface ordering by controlling cation segregation.
ACS APPLIED MATERIALS & INTERFACES
(2021)
Article
Chemistry, Analytical
Wei-Sheng Liu, Balaji Gururajan, Sui-Hua Wu, Li-Cheng Huang, Chung-Kai Chi, Yu-Lun Jiang, Hsing-Chun Kuo
Summary: In this study, aluminum nitride (AlN) thin films were deposited using radio frequency magnetron sputtering, and their properties were characterized. The optimal growth conditions for the AlN thin films were determined, and a gallium nitride (GaN) layer was successfully grown on an AlN thin film as a buffer layer using in situ continual sputtering. This research provides a less expensive method for growing high-quality GaN thin films for various applications.
Article
Nanoscience & Nanotechnology
Thomas B. Sobyra, Tyler S. Mathis, Yury Gogotsi, Paul Fenter
Summary: MXenes, a family of two-dimensional materials, are attractive for energy storage and other technologies due to their high-rate charging capabilities. In situ and operando X-ray reflectivity were used to characterize the ion intercalation process and structural changes in MXene films. Negative potential sweeps resulted in contraction of interlayer spacing and loss of electron density, likely due to Li+ ion insertion and water removal, with a continuous and discrete changes associated with capacitive charge and pseudocapacitive charging process, respectively.
ACS APPLIED MATERIALS & INTERFACES
(2021)
Article
Chemistry, Physical
Chathura de Alwis, Mikhail Trought, Ethan J. Crumlin, Slavomir Nemsak, Kathryn A. Perrine
Summary: Iron plays a crucial role in natural processes and undergoes various reactions that result in corrosion films. This study investigates the initial stages of iron surface corrosion using spectroscopy techniques. The presence of oxygen and water vapor enhances the growth of carbonates, while chloride ions migrate into the interface. Water has a significant effect on carbonate growth at low pressures, while both water and oxygen increase carbonate growth at near ambient pressures. These findings have implications for understanding catalytic and redox chemistry on iron surfaces.
APPLIED SURFACE SCIENCE
(2023)
Article
Chemistry, Inorganic & Nuclear
Georgi Popov, Goran Bacic, Charlotte Van Dijck, Laura S. Junkers, Alexander Weiss, Miika Mattinen, Anton Vihervaara, Mykhailo Chundak, Pasi Jalkanen, Kenichiro Mizohata, Markku Leskela, Jason D. Masuda, Sean T. Barry, Mikko Ritala, Marianna Kemell
Summary: Atomic layer deposition (ALD) offers excellent film uniformity and conformality for the deposition of mixed-halide perovskite films. However, ALD is only capable of depositing iodine-based halide perovskites and lacks processes for other halides. In this study, six new low temperature ALD processes for PbCl2 and PbBr2 deposition are described, which are crucial steps for depositing mixed-halide perovskites with ALD.
DALTON TRANSACTIONS
(2022)
Article
Materials Science, Multidisciplinary
Seung Hyun Kim, Eun Taek Lim, Sung Yong Park, Chee Won Chung
Summary: A two-step cyclic etching technique for copper thin films was investigated using acetylacetone/O-2 gases and Ar plasma. The copper film surfaces were modified with acetylacetone/O-2 gases and then stripped using Ar-ion sputtering. The optimized process allowed for precise delineation of fine patterns on copper films without redepositions.
ECS JOURNAL OF SOLID STATE SCIENCE AND TECHNOLOGY
(2023)
Article
Chemistry, Applied
Chiyan Liu, Qiao Dong, Yong Han, Yijing Zang, Hui Zhang, Xiaoming Xie, Yi Yu, Zhi Liu
Summary: Electrocatalysis plays a crucial role in enhancing energy efficiency, reducing carbon emissions, and meeting global energy demands in a sustainable manner. Understanding the electrochemical reaction mechanisms at the electrolyte/electrode interfaces is essential for the development of advanced renewable energy technologies. However, direct probing of real-time interfacial changes under operating conditions is challenging and requires in situ methods. In this study, a new lab-based instrument utilizing ambient pressure X-ray photoelectron spectroscopy (APXPS) was introduced for in situ chemical analysis at liquid/solid interfaces. The instrument allows the investigation of surface intermediates, chemical environments, and electronic structures during electrochemical reactions.
CHINESE JOURNAL OF CATALYSIS
(2022)
Article
Chemistry, Physical
Mindaugas Andrulevicius, Evgenii Artiukh, Gunnar Suchaneck, Sitao Wang, Nikolai A. A. Sobolev, Gerald Gerlach, Asta Tamuleviciene, Brigita Abakeviciene, Sigitas Tamulevicius
Summary: X-ray photoelectron spectroscopy was used to investigate the direct synthesis of strontium and molybdenum oxide thin films by multitarget reactive magnetron sputtering. By varying the power applied to the Mo target, films with different concentrations of Mo atoms were produced. The XPS spectra revealed that both molybdenum and strontium were in the oxidized state, with Mo bonds in a lower valence state and similar Sr spectra for all samples.
Article
Materials Science, Ceramics
Khan Alam, Mohammad B. Haider, Mohammad F. Al-Kuhaili, Khalil A. Ziq, Bakhtiar Ul Haq
Summary: Chromium nitride thin films were prepared by reactive radio frequency magnetron sputtering, and their properties were studied in relation to the nitrogen to argon flow rate ratio and film composition. The results show that the film composition, band gap, and electronic phase transition are influenced by the gas flow ratio and film composition.
CERAMICS INTERNATIONAL
(2022)
Article
Materials Science, Multidisciplinary
Pavel Ondracka, Marcus Hans, Damian M. Holzapfel, Daniel Primetzhofer, David Holec, Jochen M. Schneider
Summary: Ab initio calculations were employed to investigate the effect of oxygen concentration dependent Ti vacancies on the core electron binding energy shifts in cubic titanium oxynitride. The study confirmed that Ti vacancy concentration can be quantified by intensity of shifted components in N 1s core spectra region.
Article
Chemistry, Multidisciplinary
Maxime Van den Bossche, Jacek Goniakowski, Claudine Noguera
Summary: Ultra-thin alumina films coated on aluminum alloy surfaces are important for various applications, but their structural and stability characteristics are still not well understood. Research indicates that on NiAl(100) substrates, observed theta-alumina films correspond to thermodynamic equilibrium, rather than being influenced by kinetic effects during alloy oxidation and film growth.
Article
Materials Science, Multidisciplinary
R. Sharma, P. K. Ojha, S. K. Mishra
Summary: In this study, uniform polycrystalline YIG thin films were grown on thermally oxidized Si (100) substrates. X-ray diffraction confirmed the single-phase formation of YIG. Surface morphology and thickness of the thin films were examined using scanning electron microscopy. X-ray photoemission was used to investigate the valence state of constituent elements in the ferrimagnetic thin films with saturation magnetization of 3.11 mu s/f.u. The lowest Gilbert damping constant (a) = 4.754 x 10-3 with an inhomogeneous contribution to the linewidth of 5.04 mT was observed due to extrinsic inhomogeneous growth of the deposited films.
Article
Nanoscience & Nanotechnology
Judith Gabel, Matthias Pickem, Philipp Scheiderer, Lenart Dudy, Berengar Leikert, Marius Fuchs, Martin Stuebinger, Matthias Schmitt, Julia Kuespert, Giorgio Sangiovanni, Jan M. Tomczak, Karsten Held, Tien-Lin Lee, Ralph Claessen, Michael Sing
Summary: Thin films of transition metal oxides are affected by oxygen adatoms on the surface, leading to the formation of an electronically dead surface layer and altering the band filling and electron correlations. It is important to consider the presence of surface apical oxygen when predicting the behavior of ultrathin films of transition metal oxides.
ADVANCED ELECTRONIC MATERIALS
(2022)
Article
Chemistry, Multidisciplinary
Julian Maklar, Raul Stuehler, Maciej Dendzik, Tommaso Pincelli, Shuo Dong, Samuel Beaulieu, Alexander Neef, Gang Li, Martin Wolf, Ralph Ernstorfer, Ralph Claessen, Laurenz Rettig
Summary: In this study, the electron dynamics of the two-dimensional quantum spin Hall (QSH) candidate bismuthene were investigated using time- and angle-resolved photoemission spectroscopy. Shorter lifetimes of photocarriers in bismuthene compared to conventional semiconductors were observed, which can be attributed to the presence of topological in-gap states. This study marks a critical step toward optical control of QSH functionalities.
Article
Multidisciplinary Sciences
R. Stuehler, A. Kowalewski, F. Reis, D. Jungblut, F. Dominguez, B. Scharf, G. Li, J. Schaefer, E. M. Hankiewicz, R. Claessen
Summary: In this study, the authors demonstrate that topological protection can be lifted by pairwise coupling of 2D TI edges in close proximity. This finding opens up new possibilities for active control of topological protection through inter-edge hybridization.
NATURE COMMUNICATIONS
(2022)
Article
Chemistry, Physical
Jonas Erhardt, Maximilian Bauernfeind, Philipp Eck, Martin Kamp, Judith Gabel, Tien-Lin Lee, Giorgio Sangiovanni, Simon Moser, Ralph Claessen
Summary: Indenene, a large gap quantum spin Hall insulator, is stabilized on SiC substrates and possesses excellent structural and electronic properties. Here, we establish a simple, robust, and scalable fabrication protocol for Indenene, which involves an initial growth stage followed by a short anneal to control the coverage of indium. The specific structural and electronic properties of different coverages produce distinct experimental surface characterization, providing an efficient metric for synthesizing large scale high-quality Indenene on SiC.
JOURNAL OF PHYSICAL CHEMISTRY C
(2022)
Article
Multidisciplinary Sciences
Marcin Syperek, Raul Stuhler, Armando Consiglio, Pawel Holewa, Pawel Wyborski, Lukasz Dusanowski, Felix Reis, Sven Hofling, Ronny Thomale, Werner Hanke, Ralph Claessen, Domenico Di Sante, Christian Schneider
Summary: The optical spectroscopy of ultimately thin materials has greatly benefited our understanding of collective excitations in low-dimensional semiconductors. The authors of this study report the observation of room temperature excitons in a single layer of bismuth atoms epitaxially grown on a SiC substrate, a material with non-trivial global topology. These excitonic and topological physics arise from the same electronic structure.
NATURE COMMUNICATIONS
(2022)
Article
Chemistry, Multidisciplinary
Bing Liu, Tim Wagner, Stefan Enzner, Philipp Eck, Martin Kamp, Giorgio Sangiovanni, Ralph Claessen
Summary: By synthesizing ultrathin Sb films on semi-insulating InSb(111)A substrate, researchers observe a pronounced moire pattern on the Sb films and confirm experimentally that the topological surface state persists and shifts toward lower binding energies with a decrease in Sb thickness, in agreement with theoretical predictions.
Article
Chemistry, Physical
Lenart Dudy, Piotr Chudzinski, Julian Aulbach, Victor Rogalev, Joerg Schaefer, Ralph Claessen
Summary: In this study, we investigated the temperature dependence of the metallic-like bands of Si(553)-Au using angular-resolved photoemission spectroscopy. By overcoming the challenges posed by surface stability and photo-voltage effects, we were able to extract changes in band-filling and Fermi-velocity. Our findings shed light on the nature of the low-temperature phase of the step edge in Si(553)-Au and rule out a structural-related phase transition.
Article
Physics, Multidisciplinary
P. Kagerer, C. I. Fornari, S. Buchberger, T. Tschirner, L. Veyrat, M. Kamp, A. V. Tcakaev, V. Zabolotnyy, S. L. Morelhao, B. Geldiyev, S. Mueller, A. Fedorov, E. Rienks, P. Gargiani, M. Valvidares, L. C. Folkers, A. Isaeva, B. Buechner, V. Hinkov, R. Claessen, H. Bentmann, F. Reinert
Summary: Inducing a magnetically-induced gap in the Dirac point of a three-dimensional topological insulator can result in dissipationless charge and spin currents. In this study, the authors use a ferromagnetic extension technique to create a robust 2D ferromagnetic material on the surface of a 3D topological insulator. The results demonstrate the opening of a sizable magnetic gap in the 2D ferromagnetic phase, while the surface remains gapless in the paramagnetic phase.
PHYSICAL REVIEW RESEARCH
(2023)
Article
Materials Science, Multidisciplinary
Philipp Eck, Carmine Ortix, Armando Consiglio, Jonas Erhardt, Maximilian Bauernfeind, Simon Moser, Ralph Claessen, Domenico Di Sante, Giorgio Sangiovanni
Summary: The recently introduced classification of two-dimensional insulators in terms of topological crystalline in-variants has been extended to quantum spin Hall insulators, and an experimental fingerprint of the obstruction has been measured.
Article
Materials Science, Multidisciplinary
Suhua Jin, Yunyouyou Xia, Wujun Shi, Jiayu Hu, Ralph Claessen, Werner Hanke, Ronny Thomale, Gang Li
Summary: The chiral edge modes in the topological quantum anomalous Hall effect are crucial for future quantum technology and spintronics applications. This study proposes Al2O3 as an ideal substrate for atomic monolayers of Bi and group-III elements, where a large-gap quantum spin Hall effect can be realized. Additional half-passivation with nitrogen suggests a topological phase transition to a large-gap QAH insulator. Effective tight-binding modeling shows that the system is dominated by px, py orbitals with a subdominant pz orbital contribution. The topological phase transition is induced by Zeeman splitting, with no significant role played by off-diagonal spin exchange.
Article
Materials Science, Multidisciplinary
Yunyouyou Xia, Suhua Jin, Jiayu Hu, Ralph Claessen, Werner Hanke, Ronny Thomale, Gang Li
Summary: We extend the px-py large-gap scenario to the band inversion systems and exemplify the mechanism with a family of III-Bi honeycomb monolayers on SiO2. This work enriches the research field of large-gap quantum spin Hall systems.
Article
Materials Science, Multidisciplinary
M. Zapf, M. Schmitt, J. Gabel, P. Scheiderer, M. Stubinger, B. Leikert, G. Sangiovanni, L. Dudy, S. Chernov, S. Babenkov, D. Vasilyev, O. Fedchenko, K. Medjanik, Yu Matveyev, A. Gloskowski, C. Schlueter, T-L Lee, H-J Elmers, G. Schonhense, M. Sing, R. Claessen
Summary: Novel two-dimensional electron systems at the interfaces and surfaces of transition-metal oxides have recently gained attention for their tunable and intriguing properties. In this study, a high-mobility quasi-two-dimensional electron system with strong spin-orbit coupling was induced at the surface of a KTaO3 crystal by pulsed laser deposition of a disordered LaAlO3 film. Through angle-resolved photoelectron spectroscopy, the electronic structure of the buried electron system was mapped out. The results showed a deviation in the band structure from the bulk KTaO3 due to the confinement to the interface, and also confirmed the theoretical expectations of the confined electron system.
Article
Materials Science, Multidisciplinary
M. Schmitt, O. Kirilmaz, S. Chernov, S. Babenkov, D. Vasilyev, O. Fedchenko, K. Medjanik, Yu Matveyev, A. Gloskovskii, C. Schlueter, A. Winkelmann, L. Dudy, H-J Elmers, G. Schoenhense, M. Sing, R. Claessen
Summary: Magnetite is considered a promising material for spintronics applications due to its high spin polarization, but previous attempts to measure it were hindered by surface sensitivity and reconstruction. This study successfully determined the intrinsic spin polarization of magnetite using a novel setup and (111)-oriented thin films grown on ZnO(0001).
Article
Materials Science, Multidisciplinary
M. Stuebinger, J. Gabel, P. Scheiderer, M. Zapf, M. Schmitt, P. Schuetz, B. Leikert, J. Kuespert, M. Kamp, P. K. Thakur, T-L Lee, P. Potapov, A. Lubk, B. Buechner, M. Sing, R. Claessen
Summary: The heterostructure of LaVO3 and SrTiO3 shows promise for future photovoltaic applications due to their matching excitation gap and correlated nature at the interface. However, there is still a lack of experimental data and profound understanding of the electronic properties of the heterostructure.
