Article
Materials Science, Multidisciplinary
S. Starikov, A. Abbass, R. Drautz, M. Mrovec
Summary: This study investigates temperature-induced disordering transitions of grain boundaries in body-centered cubic metals using classical atomistic simulations. The study reveals that gradual heating leads to continuous disordering of the grain boundary structure, accompanied by two complexion transitions, analogous to transitions described by the Berezinskii-Kosterlitz-Thouless-Halperin-Nelson-Young theory.
Article
Chemistry, Physical
Jongpil Ye, Jaehoon Jeong
Summary: The grain structure of graphene significantly influences its properties, making it crucial to control for application. Inconsistent results regarding the correlation between the grain structures of graphene and underlying Cu have been found in previous investigations. Research suggests that the origin of this discrepancy lies in the effects of copper grain boundary structure on graphene growth.
Article
Nanoscience & Nanotechnology
Arava Zohar, Michael Kulbak, Silver H. Turren-Cruz, Pabitra K. Nayak, Adi Kama, Anders Hagfeldt, Henry J. Snaith, Gary Hodes, David Cahen
Summary: We present a powerful approach to assess the defect densities in lead halide perovskite materials based on electric field mapping. By measuring the electric field profile using electron beam-induced current, we deduced the defect densities and found that they mainly exist at the interfaces with selective contacts rather than in the perovskite film. These results are highly relevant for improving the efficiency of photovoltaic devices.
ACS APPLIED MATERIALS & INTERFACES
(2022)
Article
Materials Science, Multidisciplinary
A. A. Zaitsev, D. Sidorenko, I Konyashin
Summary: By using STEM/EDX techniques, WC/WC grain boundaries in ultra-coarse WC-Co hardmetals with different shapes of WC grains were examined. It was found that the state of WC-WC grain boundaries varies in hardmetals with different carbon contents, which is presumably related to the wetting rates of tungsten carbide by liquid Co-based binders.
Article
Physics, Applied
S. E. Savotchenko
Summary: New phenomenological models of recrystallization of a polycrystalline material, considering the finite width of grain boundaries, were proposed. Analytical solutions for the initial-boundary value problems were obtained, describing the distributions of impurity concentration diffusing from the surface coating in both grain boundaries and the recrystallized grain region. The speed of recrystallization front movement was indicated to be consistent with experimental observations of corresponding kinetic dependences.
MODERN PHYSICS LETTERS B
(2022)
Article
Materials Science, Multidisciplinary
Jingxiao Ren, Hongxian Xie, Fuxing Yin, Guanghong Lu
Summary: In this study, the impact of grain boundaries on the growth of helium bubbles was investigated. It was found that low-angle symmetrical tilt grain boundaries can form helium nanochannels and release helium outside of the tungsten matrix, which may be a potential strategy to address bubble nucleation and swelling.
JOURNAL OF NUCLEAR MATERIALS
(2023)
Article
Materials Science, Multidisciplinary
Xingyu Feng, Qi Wang, Jiayu Xie, Wenjun Kuang
Summary: The intergranular degradation of Alloy 600 was studied in simulated pressurized water reactor primary water for seven different types of high-angle grain boundaries. All boundaries exhibited susceptibility to preferential intergranular oxidation (PIO), except for the ideal coherent twin boundary. Diffusion induced grain boundary migration (DIGM) typically occurred, and its depth was positively correlated with the extent of PIO. Interestingly, the PIO susceptibility was independent of the grain boundary misorientation angle or σ value, but related to the grain boundary atom packing density (GBAPD), where higher GBAPD values correlated with higher PIO resistance due to slower element diffusion.
Article
Chemistry, Physical
Yang He, Yunjuan Su, Haobo Yu, Changfeng Chen
Summary: This study investigated the trapping sites and diffusion behaviors of hydrogen atoms in different iron grain boundary structures through first-principles calculations. The diffusion behavior of hydrogen in grain boundaries was found to have an impact on hydrogen embrittlement phenomenon.
INTERNATIONAL JOURNAL OF HYDROGEN ENERGY
(2021)
Article
Materials Science, Multidisciplinary
Diana Farkas
Summary: Molecular Dynamics simulations were used to study the diffusion process along a grain boundary in a model austenitic stainless steel. The results showed that Cr diffuses about 25 percent faster than Fe or Ni, and the diffusion kinetics varied widely among different general high angle boundaries. Faster diffusion kinetics were associated with higher energy grain boundaries and narrower boundaries with more extra volume and less centrosymmetric structure.
METALLURGICAL AND MATERIALS TRANSACTIONS A-PHYSICAL METALLURGY AND MATERIALS SCIENCE
(2021)
Article
Materials Science, Multidisciplinary
David E. Page, Kathryn F. Varela, Oliver K. Johnson, David T. Fullwood, Eric R. Homer
Summary: This study investigates the impact of nickel grain boundaries on hydrogen diffusion through simulations of 26 different types of grain boundaries. It is found that grain boundary diffusivity is higher than bulk diffusivity within a certain temperature range, and the Borisov relationship fits well with simulated data, providing physically realistic parameter estimates.
Article
Electrochemistry
Susmita Sarkar, John Alexander Hoffmann, Jonghyun Park
Summary: This study investigates the impact of grain boundaries on battery performance, revealing that grain boundary diffusion significantly affects the voltage profile and maximum stress in the cell. Variability in grain structure geometry results in particles with lower diffusion at the rear side enduring more stress than highly diffusive frontal particles.
ELECTROCHIMICA ACTA
(2021)
Article
Chemistry, Physical
Xiang Xi, D. D. L. Chung
Summary: In graphite, the interaction between carrier atoms that causes electric polarization occurs at grain boundaries, with the electric permittivity being linearly related to the reciprocal of grain size. Smaller grain size increases permittivity by increasing the fraction of carriers participating in polarization. The interaction at grain boundaries is the main factor determining the permittivity and participation of carriers.
Article
Chemistry, Physical
Artem M. Abakumov, Chen Li, Anton Boev, Dmitry A. Aksyonov, Aleksandra A. Savina, Tatiana A. Abakumova, Gustaaf Van Tendeloo, Sara Bals
Summary: High-energy lithium-rich layered transition metal oxides exhibit complex electrochemical behavior due to interactions between crystal, electronic, and defect structures. This study reveals that grain boundary microstructures, particularly Na-enriched regions, have a significant impact on the rate capability of Li-rich cathodes, affecting the diffusion of Li+ ions.
ACS APPLIED ENERGY MATERIALS
(2021)
Article
Materials Science, Ceramics
Jingjing Sun, Yu-Wei You, Xuebang Wu, Hong-Yue Song, B. S. Li, C. S. Liu, Vladimir Krsjak
Summary: In SiC ceramics, helium tends to aggregate at grain boundaries, but the interaction mechanisms between helium and grain boundaries are still unclear. In this study, first-principles calculations show that helium easily segregates at grain boundaries with open structures and low charge density, and these grain boundaries significantly enhance helium diffusion.
JOURNAL OF THE EUROPEAN CERAMIC SOCIETY
(2022)
Review
Chemistry, Multidisciplinary
Maolin Yu, Zhili Hu, Jingzhuo Zhou, Yang Lu, Wanlin Guo, Zhuhua Zhang
Summary: This review article summarizes recent advances in studying the formation mechanism, atomic structures, and functional properties of grain boundaries (GBs) in 2D materials. A complete understanding of the rich GB morphologies, their dependence on lattice misorientations and chemical compositions, is presented by analyzing the growth mechanism and the competition between far-field strain and local chemical energies of dislocation cores. The mechanical, electronic, and chemical properties tied to GBs in different materials are discussed, along with the concept of using GBs as a robust atomic-scale scaffold for realizing tailored functionalities such as magnetism, luminescence, and catalysis. Future opportunities in retrieving GBs for making functional devices and the major challenges in the controlled formation of GB structures for designed applications are also commented.
Article
Chemistry, Inorganic & Nuclear
M. V. Dorokhin, O. V. Vikhrova, P. B. Demina, I. L. Kalentyeva, P. S. Vergeles, E. B. Yakimov, V. P. Lesnikov, B. N. Zvonkov, M. V. Ved, Yu. A. Danilov, A. V. Zdoroveyshchev
Summary: This study investigated GaAs semiconductor structures for betavoltaic power sources and found that deposition of a carbon layer can improve the performance of the Schottky structure.
APPLIED RADIATION AND ISOTOPES
(2022)
Letter
Materials Science, Coatings & Films
Eugene B. Yakimov, Alexander Y. Polyakov, Stephen J. Pearton
Summary: The parameters of betavoltaic cells based on a Ni/beta-Ga2O3 Schottky barrier diode and beta-particle source containing Ni-63 are evaluated. The depth-dependent generation rate of excess carriers produced by beta-radiation from Ni-63 source is calculated using Monte Carlo simulation, and it is found that the dependence can be described by an exponential function.
JOURNAL OF VACUUM SCIENCE & TECHNOLOGY A
(2022)
Review
Materials Science, Coatings & Films
Alexander Y. Polyakov, Vladimir I. Nikolaev, Eugene B. Yakimov, Fan Ren, Stephen J. Pearton, Jihyun Kim
Summary: This paper reviews the reported trap states in the bandgaps of different polymorphs of the emerging ultrawide bandgap semiconductor Ga2O3. The crystalline defects adversely affect the material properties critical to device operation and lead to degraded device operating speed characterized by long recovery transients. More research is needed to understand the microscopic nature of defects in Ga2O3.
JOURNAL OF VACUUM SCIENCE & TECHNOLOGY A
(2022)
Article
Materials Science, Multidisciplinary
Eugene E. Yakimov, Eugene B. Yakimov
Summary: The expansion of single-layer Shockley-type stacking faults (SSF) in 4H-SiC due to irradiation has been studied. It is found that the focused e-beam enhances the glide of 30 degrees Si-core partial dislocations at room and liquid nitrogen temperatures within a certain distance. The velocity of the dislocations remains constant regardless of their length, and the velocity is determined by the double kink generation rate.
PHYSICA STATUS SOLIDI A-APPLICATIONS AND MATERIALS SCIENCE
(2022)
Article
Nanoscience & Nanotechnology
A. Y. Polyakov, V. I. Nikolaev, A. I. Pechnikov, S. I. Stepanov, E. B. Yakimov, M. P. Scheglov, I. V. Shchemerov, A. A. Vasilev, A. A. Kochkova, A. V. Chernykh, A. V. Chikiryaka, S. J. Pearton
Summary: Thick films (23 μm) of kappa-Ga2O3 were successfully grown on GaN/sapphire templates using Halide Vapor Phase Epitaxy (HVPE). The films exhibited good crystalline quality and surface morphology. They possessed specific properties such as a wide absorption band and deep-level traps.
Article
Physics, Applied
Alexander Y. Polyakov, Vladimir Nikolaev, Igor N. Meshkov, Krzysztof Siemek, Petr B. Lagov, Eugene B. Yakimov, Alexei Pechnikov, Oleg S. Orlov, Alexey A. Sidorin, Sergey Stepanov, Ivan Shchemerov, Anton A. Vasilev, Alexey Chernykh, Anton A. Losev, Alexandr D. Miliachenko, Igor A. Khrisanov, Yu S. Pavlov, U. A. Kobets, Stephen J. Pearton
Summary: Films of alpha-Ga2O3 grown by Halide Vapor Phase Epitaxy (HVPE) were characterized after irradiation with protons and C ions, revealing the introduction of defect-related energy levels and the formation of a conducting layer.
JOURNAL OF APPLIED PHYSICS
(2022)
Article
Chemistry, Physical
In-Hwan Lee, Tae-Hwan Kim, A. Y. Polyakov, A. V. Chernykh, M. L. Skorikov, E. B. Yakimov, L. A. Alexanyan, I. V. Shchemerov, A. A. Vasilev, S. J. Pearton
Summary: In this study, a matrix of blue GaN/InGaN multi-quantum-well micro-LEDs was prepared and characterized. The changes in photoluminescence and microcathodoluminescence spectra were found to be related to the formation of deep hole traps and electron traps in the sidewalls of the micro-LEDs.
JOURNAL OF ALLOYS AND COMPOUNDS
(2022)
Article
Materials Science, Multidisciplinary
V. I. Nikolaev, A. Y. Polyakov, S. I. Stepanov, A. I. Pechnikov, E. B. Yakimov, A. V. Chernykh, A. A. Vasilev, I. V. Shchemerov, A. I. Kochkova, L. Guzilova, M. P. Konovalov, S. J. Pearton
Summary: Two-inch diameter alpha-Ga2O3 films with a thickness of about 4 μm were successfully grown on basal plane sapphire using HVPE. The films were characterized using various techniques, revealing low dislocation densities, smooth surface, and varied sheet resistivity. Furthermore, the donor concentration and deep trap levels were also observed.
ECS JOURNAL OF SOLID STATE SCIENCE AND TECHNOLOGY
(2022)
Article
Chemistry, Multidisciplinary
Sergei Koveshnikov, Oleg Kononenko, Oleg Soltanovich, Olesya Kapitanova, Maxim Knyazev, Vladimir Volkov, Eugene Yakimov
Summary: Graphene oxide, among various graphene derivatives, is the most studied material due to its reliable and repeatable resistive switching properties. Researchers have identified three operative mechanisms responsible for this resistive switching, including metallic-like filamentary conduction, contact resistance modification, and oxidation/reduction in the bulk of graphene oxide.
Article
Materials Science, Multidisciplinary
S. I. Stepanov, V. I. Nikolaev, A. Y. Polyakov, A. I. Pechnikov, E. B. Yakimov, M. P. Scheglov, I. V. Shchemerov, A. A. Vasilev, A. A. Kochkova, A. V. Chernykh, A. V. Chikiryaka, P. N. Butenko, S. J. Pearton
Summary: This study successfully grew Ga2O3 layers with thickness ranging from 10 to 86 μm using halide vapor phase epitaxy (HVPE) on GaN(0001)/sapphire templates. The grown layers were pure (001)-oriented kappa-Ga2O3 phase without admixture of other phases. The best crystal quality was observed in 13-20 μm thick kappa-Ga2O3 layers, while an increase in thickness led to deterioration indicated by broadening of rocking curves. Electrical measurements showed that the grown layers were n-type with decreasing concentration of shallow donors and deep level transient spectroscopy (DLTS) revealed the presence of deep traps with varying energy levels.
ECS JOURNAL OF SOLID STATE SCIENCE AND TECHNOLOGY
(2023)
Review
Energy & Fuels
Eugene B. Yakimov
Summary: This article reviews the approaches for predicting output parameters of betavoltaic batteries, discusses the need to develop a strategy for accurate prediction without using trial and error, and analyzes the strengths and weaknesses of previously proposed approaches. It also simulates the depth dependencies of beta particles deposited energy for different materials and radioisotope sources, calculates the maximum short circuit current densities, and describes a methodology for predicting betavoltaic cell output parameters with high accuracy.
Article
Materials Science, Multidisciplinary
A. Y. Polyakov, A. V. Almaev, V. I. Nikolaev, A. I. Pechnikov, V. I. Shchemerov, A. A. Vasilev, E. B. Yakimov, A. I. Kochkova, V. V. Kopyev, B. O. Kushnarev, S. J. Pearton
Summary: The influence of deep centers on photocurrent spectra and transients of interdigitated photoresistors on alpha-Ga2O3 undoped semi-insulating films was investigated. Characterization techniques including current-voltage measurements, Thermally Stimulated Current (TSC), and Photoinduced Current Transients Spectroscopy (PICTS) revealed the presence of deep acceptors and deep traps, along with a pinned Fermi level at E-c-0.8 eV. Photocurrent transients and Electron Beam Induced Current (EBIC) imaging indicated that the high sensitivity and external quantum efficiency values were attributed to hole trapping, which enhanced the electron lifetime and were associated with long photocurrent transients. The stretched exponents observed in the photocurrent transients suggest the contribution of centers with electron capture barriers and/or potential fluctuations.
ECS JOURNAL OF SOLID STATE SCIENCE AND TECHNOLOGY
(2023)
Article
Chemistry, Analytical
Eugene B. Yakimov, Yury O. Kulanchikov, Pavel S. Vergeles
Summary: The dynamics of dislocations introduced into GaN layers grown using different methods and with different dislocation densities were investigated. It was found that dislocation glide in GaN is possible even at room temperature with a lower than 1 eV Peierls barrier. The mobility of dislocations in GaN is determined by both overcoming the Peierls barrier and localized obstacles. Thread dislocations were found to be effective obstacles for basal plane dislocation glide. Under low-energy electron beam irradiation, the activation energy for dislocation glide decreases, indicating that localized obstacles become the main controlling factor.
Article
Chemistry, Multidisciplinary
Eugene B. B. Yakimov, Alexander Y. Y. Polyakov, Vladimir I. I. Nikolaev, Alexei I. I. Pechnikov, Mikhail P. P. Scheglov, Eugene E. E. Yakimov, Stephen J. J. Pearton
Summary: This study investigates the properties of orthorhombic kappa-Ga2O3 films prepared using Halide Vapor Phase Epitaxy (HVPE) on AlN/Si and GaN/sapphire templates. The formation of two-dimensional hole layers and the suppression of rotational nanodomains are studied. Good rectifying characteristics of Ni Schottky diodes are observed in thick kappa-Ga2O3 films grown on GaN/sapphire. The presence of deep electron traps near E-c - 0.3 eV and E-c - 0.7 eV is found in the uppermost layer of the grown kappa-Ga2O3 films, resulting in relatively high series resistance.
Article
Chemistry, Multidisciplinary
Eugene B. Yakimov, Sergei Koveshnikov, Oleg Kononenko
Summary: The electron-beam-induced current (EBIC) method was used to visualize conductive channels formed in graphene oxide due to resistive switching. By using metal-insulator-semiconductor (MIS) structures, a significant increase in the EBIC signal compared to metal-insulator-metal (MIM) structures was achieved. The formation of conductive channels was explained by the separation and collection of excess carriers generated by the e-beam at rectifying barrier nanocontacts formed at the graphene oxide/Si interface. The EBIC method demonstrated an important advantage in monitoring the generation and elimination of high density conductive channels that current-voltage measurements cannot detect and separate.
APPLIED SCIENCES-BASEL
(2023)
