A5073877208- Electronic and Structural Properties of Oxides
- Semiconductor materials and devices
- Advanced Memory and Neural Computing
- Ga2O3 and related materials
- Magnetic and transport properties of perovskites and related materials
- ZnO doping and properties
- Ferroelectric and Negative Capacitance Devices
- Advanced Photocatalysis Techniques
- Advanced Condensed Matter Physics
- Neuroscience and Neural Engineering
- Perovskite Materials and Applications
- Metal and Thin Film Mechanics
- Ferroelectric and Piezoelectric Materials
- Diamond and Carbon-based Materials Research
- Gas Sensing Nanomaterials and Sensors
- Copper Interconnects and Reliability
- Catalytic Processes in Materials Science
- Nuclear materials and radiation effects
- Phase-change materials and chalcogenides
- Surface and Thin Film Phenomena
- Wastewater Treatment and Nitrogen Removal
- Thin-Film Transistor Technologies
- Block Copolymer Self-Assembly
- Neural Networks and Reservoir Computing
- Boron and Carbon Nanomaterials Research
Max Planck Institute for Solid State Research
2023-2025
Cornell University
2020-2024
Interface (United States)
2021-2022
University of St Andrews
2022
Forschungszentrum Jülich
2017-2021
Jülich Aachen Research Alliance
2019-2021
United States Air Force Research Laboratory
2021
Pennsylvania State University
2021
RWTH Aachen University
2013-2021
This paper introduces a growth method—suboxide molecular-beam epitaxy (S-MBE)—which enables drastic enhancement in the rates of Ga2O3 and related materials to over 1 μm h−1 an adsorption-controlled regime, combined with excellent crystallinity. Using Ga + mixture oxygen mole fraction x(O) = 0.4 as MBE source, we overcome kinetic limits that had previously hampered by MBE. We present up 1.6 1.5 for Ga2O3/Al2O3 Ga2O3/Ga2O3 structures, respectively, very high crystalline quality at unparalleled...
We report the use of suboxide molecular-beam epitaxy (S-MBE) to grow β-Ga2O3 at a growth rate ∼1 µm/h with control silicon doping concentration from 5 × 1016 1019 cm−3. In S-MBE, pre-oxidized gallium in form molecular beam that is 99.98% Ga2O, i.e., suboxide, supplied. Directly supplying Ga2O surface bypasses rate-limiting first step two-step reaction mechanism involved by conventional MBE. As result, readily achieved relatively low temperature (Tsub ≈ 525 °C), resulting films high...
Oxides have attracted enormous attention for both application-driven and fundamental solid-state research owing to their broad range of unusual unique properties. play an important role in countless applications, e.g., as catalysts or functional materials electronic devices. The ability produce high-quality epitaxial films is often crucial these purposes. Various approaches oxide epitaxy been evolving many years, each which has its own features strengths. However, also poses numerous...
Abstract The reduction of oxides during annealing and growth in low pressure processes is a widely known problem. We hence investigate the influence mere vacuum systems to shed light on reasons behind perovskites. When comparing existing literature regarding perovskite model material SrTiO 3 it conspicuous that one finds different oxygen pressures required achieve for chemically controlled reducing atmospheres. unraveling this discrepancy high interest physical vapor depositions thin films...
Pulsed Laser Deposition is a commonly used non-equilibrium physical deposition technique for the growth of complex oxide thin films. A wide range parameters known to influence properties samples and films, especially oxygen-vacancy concentration. One parameter has up this point been neglected due challenges separating its from impinging species during growth: UV-radiation plasma plume. We here present experiments enabled by specially designed holder allow separation these two influences. The...
The growth of a wide range binary nitride films with excellent properties is reported. These are deposited by thermal laser epitaxy (TLE). If equipped CO2–laser substrate heating, TLE allows temperatures ≫ 1000 °C combined strong nitriding conditions, which established using ammonia (NH3) gas as nitrogen precursor. Films on c-plane sapphire substrates include semiconducting nitrides (BN, AlN, ScN, and YN), superconducting (TiN, VN, ZrN, NbN), magnetic (CrN GdN). transition TiN, NbN 5.7, 8.9,...
We observe a catalytic mechanism during the growth of III-$\mathrm{O}$ and IV-$\mathrm{O}$ materials by suboxide molecular-beam epitaxy ($S$-MBE). By supplying molecular catalysts ${\mathrm{In}}_{2}\mathrm{O}$ SnO we increase rates ${\mathrm{Ga}}_{2}{\mathrm{O}}_{3}$ ${\mathrm{In}}_{2}{\mathrm{O}}_{3}$. This action is explained metastable adlayer $A$, which increases reaction probability reactants ${\mathrm{Ga}}_{2}\mathrm{O}$ with active atomic oxygen, leading to an derive model for binary...
β -Ga2O3 is actively touted as the next ultrawide bandgap material for power electronics. To fully utilize its high intrinsic critical electric field, development of high-quality robust large-barrier height junctions essential. this end, various high-work function metals, metal oxides, and hole-conducting oxides have been deposited on Ga2O3, primarily formed by sputter deposition. Unfortunately, reports to date indicate that measured barrier heights often deviate from Schottky–Mott model...
Sapphire is a technologically highly relevant material, but it poses many challenges when performing epitaxial thin-film deposition. We have identified and applied the conditions for adsorption-controlled homoepitaxial growth of c-plane sapphire. The films thus grown are atomically smooth, controlled termination, outstanding crystallinity. Their chemical purity exceeds that substrates. exhibit exceptional optical properties, such as single-crystal-like bandgap low density F+ centers.
Point defects such as oxygen vacancies cause emergent phenomena resistive switching in transition-metal oxides, but their influence on the electron-transport properties is far from being understood. Here, we employ direct mapping of electronic structure a memristive device by spectromicroscopy. We find that result in-gap states use input for single-band transport simulations. Because are situated below Fermi level, they do not contribute to current directly impact shape conduction band....
Abstract Resistive switching in transition metal oxide‐based metal‐insulator‐metal structures relies on the reversible drift of ions under an applied electric field nanoscale. In such structures, formation conductive filaments is believed to be induced by electric‐field driven migration oxygen anions, while cation sublattice often considered inactive. This simple mechanistic picture process incomplete as both anions and cations have been previously identified mobile species device operation....
We present a study of the trade-off between retention and variability SrTiO3-based memristive devices. identified applied switching current device stoichiometry as main influence factors. show that SrO formation at electrode interface, which has been revealed to improve significantly, is associated with an increased cycle-to-cycle device-to-device variability. On other hand, devices homogeneous, Ti-terminated SrTiO3–Pt interfaces exhibit poor but smallest These results give valuable insights...
Molecular-beam epitaxy (MBE) is the gold standard for epitaxial growth of complex oxides with best material properties as determined by respective figures merit. Unfortunately, once more than one cation involved in desired, MBE often becomes plagued difficulties stoichiometry control. Instead relying on a quartz crystal microbalance to measure fluxes individual molecular beams, which lacks accuracy, or reflection high-energy electron diffraction oscillations targeted multication oxide...
Aluminum plays a central role in the world of electronic oxide materials. Yet, aluminum sources are very difficult to handle during molecular-beam epitaxy, main reason for which is high oxidization potential aluminum. In this work, we present thorough study behavior thermal laser epitaxy. We identify two distinct operating regimes. At laser-beam fluences, source emanates reproducible fluxes independent an applied oxygen pressure <10−1 hPa. lower beam flux increases with increasing...
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Abstract Substrates are essential in thin‐film deposition, yet they do not always meet the requirements of a given application. For example, might be prohibitively expensive or even available with necessary crystal lattice structures. This paper introduces innovative concept “vector substrates,” where template layer for growth, referred to as vector, is chemically and crystallographically independent bulk substrate. approach reduces material costs offers unparalleled flexibility. The...
We here present a method to engineer Ruddlesden-Popper-type antiphase boundaries in stoichiometric homoepitaxial SrTiO3 thin films. This is achieved by using substrate with an intentionally high miscut, which stabilizes the growth of additional SrO at bottom interface. prove success this strategy utilizing transmission electron microscopy. find that these significantly influence resistive switching properties. In particular, devices based on films induced do not require forming step,...
We have developed and optimized a method to grow ruthenium films of unprecedented quality. Our three-step process is reminiscent solid-phase epitaxy. First, c-cut sapphire substrates are terminated at their Al-rich √31 × √31R ± 9° reconstruction by in situ annealing. Second, 3D structured epitaxial Ru deposited low temperatures laser evaporation rods. Third, the films, thus, obtained epitaxially transformed high-temperature X-ray diffraction studies reveal good crystallinity 15–60 nm-thick...
Superconducting films of α-Ta are promising candidates for the fabrication advanced superconducting qubits. However, suffer from many growth-induced structural inadequacies that negatively affect their performance. We have therefore explored a new synthesis method films, which allows growth these with an unprecedented quality. Using this method, high quality deposited at comparably substrate temperature 1150 °C. They single-phase and single out-of-plane (110) orientation. consist grains ≥2...
Solid-state diffusion experiments were used to probe the behavior of cation vacancies in perovskite oxide ${\mathrm{SrTiO}}_{3}$. Two types nominally undoped (effectively acceptor-doped) ${\mathrm{SrTiO}}_{3}$ systems studied: (1) single crystals and (2) epitaxial thin films with different Sr/Ti stoichiometries produced by pulsed laser deposition. As sources, ${\mathrm{BaZrO}}_{3}$ employed, anneals carried out air at $1323\ensuremath{\le}T/\mathrm{K}\ensuremath{\le}1523$ for...
We demonstrate the epitaxial growth of first two members, and n=∞ member homologous Ruddlesden–Popper series Ban+1InnO2.5n+1 which n=1 was previously unknown. The films were grown by suboxide molecular-beam epitaxy where indium is provided a molecular beam indium-suboxide [In2O (g)]. To facilitate ex situ characterization highly hygroscopic barium indate films, capping layer amorphous SiO2 deposited prior to air exposure. structural quality assessed x-ray diffraction, reflective high-energy...