Article
Nanoscience & Nanotechnology
Ymir K. Frodason, Patryk P. Krzyzaniak, Lasse Vines, Joel B. Varley, Chris G. Van de Walle, Klaus Magnus H. Johansen
Summary: The diffusion of the n-type dopant Sn in beta-Ga2O3 was studied using secondary-ion mass spectrometry combined with hybrid functional calculations. It was found that Ga vacancies mediate the migration of Sn through the formation and dissociation of intermittent mobile VGaSnGa complexes. The migration barrier for the VGaSnGa complex was determined to be 3.0 +/- 0.4 eV, consistent with theoretical predictions using the nudged elastic band method.
Article
Nanoscience & Nanotechnology
Hemant Ghadi, Joe F. McGlone, Evan Cornuelle, Zixuan Feng, Yuxuan Zhang, Lingyu Meng, Hongping Zhao, Aaron R. Arehart, Steven A. Ringel
Summary: This study evaluates the defect state distribution in beta phase gallium oxide (beta-Ga2O3) grown by low-pressure chemical vapor deposition (LPCVD). The presence of a previously unreported defect state and other known defect states were observed. The trap concentration in the LPCVD-grown material was lower compared to materials grown by other methods, and the distribution of the defect states showed little dependence on the SiCl4 flow rate and doping concentration. These findings indicate that LPCVD-grown beta-Ga2O3 has great potential for producing thick, low-defect density, and high-quality layers for multi-kV device applications.
Article
Physics, Applied
Johanna Uhlendorf, Zbigniew Galazka, Harald Schmidt
Summary: The study investigated oxygen tracer self-diffusion in monoclinic gallium oxide single crystals at high temperatures using O-18(2) gas as a tracer source. The diffusivities follow the Arrhenius law with an activation enthalpy of (3.2±0.4) eV. Oxygen interstitials are suggested to be more dominant than vacancies in governing diffusion.
APPLIED PHYSICS LETTERS
(2021)
Article
Engineering, Electrical & Electronic
Shaozhong Yue, Xuefeng Zheng, Yuehua Hong, Xiangyu Zhang, Fang Zhang, Yingzhe Wang, Xiaohua Ma, Yue Hao
Summary: This study investigates the effect of neutron irradiation on the electrical performance of the beta-Ga2O3 Schottky barrier diode (SBD) device. The results show that after neutron irradiation, there is a decrease in forward current density (J(F)), reduction in reverse current density (J(R)), and increase in breakdown voltage (V-br) based on current-voltage (I-V) measurements. The density of interface states slightly increases, and there is an increase in trap activation energy after neutron irradiation according to frequency-dependent conductance technique. The carrier concentration across the Ga2O3 drift layer decreases after neutron irradiation based on capacitance-voltage (C-V) measurements.
IEEE TRANSACTIONS ON ELECTRON DEVICES
(2023)
Article
Physics, Applied
M. M. Chang, D. Y. Guo, X. L. Zhong, F. B. Zhang, J. B. Wang
Summary: The influence of high-energy proton irradiation on beta-Ga2O3 solar-blind photodetectors was investigated. Proton irradiation led to an increase in oxygen vacancies and carrier migration at the metal/semiconductor interface driven by bias. The results showed a slight increase in photoresponsivity and exhibited apparent hysteresis loops.
JOURNAL OF APPLIED PHYSICS
(2022)
Article
Physics, Applied
T. D. Gustafson, J. Jesenovec, C. A. Lenyk, N. C. Giles, J. S. McCloy, M. D. McCluskey, L. E. Halliburton
Summary: Electron paramagnetic resonance (EPR) is utilized to identify and characterize neutral zinc acceptors in Zn-doped beta-Ga2O3 crystals. The study reveals the presence of two types of Zn acceptors, Zn-Ga (0)(1) and Zn-Ga (0)(2), and investigates their interactions and thermal stability.
JOURNAL OF APPLIED PHYSICS
(2021)
Article
Chemistry, Physical
Abay Usseinov, Zhanymgul Koishybayeva, Alexander Platonenko, Vladimir Pankratov, Yana Suchikova, Abdirash Akilbekov, Maxim Zdorovets, Juris Purans, Anatoli I. Popov
Summary: The study used first-principles density functional theory and supercell approach to simulate oxygen and gallium vacancies in β-Ga2O3 crystals. The results showed that oxygen vacancy acts as a deep donor defect, while gallium vacancies serve as deep acceptors, making them unsuitable sources for p-type conductivity.
Article
Physics, Applied
A. Karjalainen, P. M. Weiser, I. Makkonen, V. M. Reinertsen, L. Vines, F. Tuomisto
Summary: The study found that hydrogen passivates V-Ga defects in beta-Ga2O3 single crystals during annealing, and the 600 degrees Celsius annealing promotes the formation of complexes containing D or other defects.
JOURNAL OF APPLIED PHYSICS
(2021)
Article
Physics, Applied
N. H. Nickel, K. Geilert
Summary: The hydrogen bonding in beta-Ga2O2 was investigated through hydrogen effusion measurements, showing a decrease in total H concentration with increasing deposition temperature. The hydrogen density-of-states distribution changes with deposition temperature, exhibiting different peaks at varying energy levels below the H transport states.
JOURNAL OF APPLIED PHYSICS
(2021)
Article
Physics, Applied
Minwei Liu, Mingzhuo Hua, Xusheng Tian, Zhengxing Wang, Huhu Gao, Wentao Wang, Yiqiang Chen, Chunfu Zhang, Shenglei Zhao, Qian Feng, Yue Hao
Summary: This study investigated the radiation effect of gamma irradiation on Au/Ni/beta-Ga2O3 vertical Schottky barrier diodes (SBDs). It was found that the irradiated SBDs showed improvements in Schottky barrier height, ideality factor, and specific on-resistance. The results suggest that beta-Ga2O3 SBDs have high intrinsic gamma irradiation hardness.
APPLIED PHYSICS LETTERS
(2023)
Article
Engineering, Electrical & Electronic
Kejia Wang, Rongxing Cao, Bo Mei, Hongwei Zhang, He Lv, Lin Zhao, Yuxiong Xue, Xianghua Zeng
Summary: This study investigates the effects of 80 MeV high-energy proton irradiation on beta-Ga2O3 single crystals. It is found that irradiation increases gallium and oxygen vacancies, resulting in a reduction of the bandgap. Proton irradiation at 80 MeV is more likely to produce oxygen vacancies, causing the Fermi level to shift upward to the conduction band, and enhancing UV photoluminescence emission.
JOURNAL OF ELECTRONIC MATERIALS
(2023)
Article
Materials Science, Multidisciplinary
Johanna Uhlendorf, Harald Schmidt
Summary: This research investigates the tracer diffusion of oxygen and aluminum in beta-Ga2O3 crystals and analyzes the different diffusion mechanisms. The results show that the diffusion of aluminum is two orders of magnitude higher than that of oxygen.
PHYSICAL REVIEW MATERIALS
(2023)
Article
Chemistry, Physical
Suiting Ning, Shan Huang, Ziye Zhang, Bin Zhao, Renqi Zhang, Ning Qi, Zhiquan Chen
Summary: The thermoelectric properties of intrinsic n-type β-Ga2O3 were evaluated using first-principles calculations and transport theory. A large Seebeck coefficient and good electron mobility were observed. The lattice thermal conductivity can be reduced by adjusting the grain size. These findings suggest the potential application of β-Ga2O3 in high temperature thermoelectric conversion.
PHYSICAL CHEMISTRY CHEMICAL PHYSICS
(2022)
Article
Materials Science, Coatings & Films
Vyacheslav Vasyltsiv, Andriy Luchechko, Yaroslav Zhydachevskyy, Lyudmyla Kostyk, Roman Lys, Dmytro Slobodzyan, Rafal Jakiela, Bohdan Pavlyk, Andrzej Suchocki
Summary: The optical properties of beta-Ga2O3:Cr crystals can be significantly improved by annealing in oxygen atmosphere and codoping with magnesium, resulting in increased Cr3+ luminescence yield and resistivity changes.
JOURNAL OF VACUUM SCIENCE & TECHNOLOGY A
(2021)
Article
Physics, Applied
Jinyang Liu, Zhao Han, Lei Ren, Xiao Yang, Guangwei Xu, Weibing Hao, Xiaolong Zhao, Shu Yang, Di Lu, Yuncheng Han, Xiaohu Hou, Shibing Long
Summary: This study systematically investigates the degradation mechanism of beta-Ga2O3 Schottky barrier diodes (SBDs) under high fluence neutron irradiation and explores a possible design roadmap. It reveals that the capture reaction of neutrons and Ga elements leads to serious performance degradation, while high-temperature oxygen annealing process can restore the device performance.
APPLIED PHYSICS LETTERS
(2023)
Article
Physics, Condensed Matter
Giovanni Alfieri, Stephan Wirths, Dan Buca, Roberta Nipoti
Summary: This study investigates the electrical characteristics of manganese ion implantation and finds that it generates various majority and minority carrier traps, most of which are associated with intrinsic defects. The results show that box-profile implanted layers exhibit high resistivity after high-temperature treatments.
PHYSICA STATUS SOLIDI B-BASIC SOLID STATE PHYSICS
(2023)
Article
Chemistry, Physical
Henry Yu, Stephen E. Weitzner, Joel B. Varley, Brandon C. Wood, Sneha A. Akhade
Summary: The electrochemical reduction of CO2 with Cu based catalysts is closely related to the instantaneous local chemical environment of the catalyst-electrolyte interface. This microenvironment fluctuates depending on the concentration of surface-adsorbed competing reaction intermediates and the applied electrode potential. Quantifying the complex interdependence between electrode potential, CO* coverage, and the interfacial field strength, our study reveals the strong influence of CO* coverage on the field strength, suggesting its significance in determining the selectivity towards multicarbon products. Additionally, our results demonstrate the potential of surface additives to modulate interfacial fields for tailored electrochemical pathways.
JOURNAL OF PHYSICAL CHEMISTRY C
(2023)
Article
Materials Science, Multidisciplinary
Andrew J. E. Rowberg, Meng Li, Tadashi Ogitsu, Joel B. Varley
Summary: In this study, first-principles calculations based on density functional theory were used to investigate the properties of hole and electron polarons in barium zirconate (BZO) and barium cerate (BCO). It was found that hole polarons form in both materials, more favorably in BCO. Electron polarons, on the other hand, are stable only in BCO and Ce-containing alloys. Doping BZO and BCO can lead to negligible electron concentrations and larger concentrations of holes and hole polarons.
PHYSICAL REVIEW MATERIALS
(2023)
Article
Materials Science, Multidisciplinary
Alexander A. Baker, Alfred Amon, Emily E. Moore, Hunter B. Henderson, Jibril Shittu, Connor J. Rietema, Aurelien Perron, Scott K. McCall
Summary: Doping of magnetostrictive galfenol (Fe82Ga18) with even extremely dilute Ce (as little as 65 ppm) can double the magnetostrictive response when coupled with an appropriate heat treatment. The improvement is correlated with a compression of the host lattice, both of which reach their maximum at the calculated solubility limit of Ce in in body-centered cubic (bcc) galfenol, similar to 50 ppm. Excess Ce segregates into CeGa2, forming an interdendritic network, which cannot be resolved through heat treatments. These findings highlight the importance of solubility limits in determining doping levels and heat treatment for optimal magnetostrictive performance.
PHYSICAL REVIEW MATERIALS
(2023)
Article
Physics, Applied
A. Y. Polyakov, A. I. Kochkova, A. Azarov, V. Venkatachalapathy, A. V. Miakonkikh, A. A. Vasilev, A. V. Chernykh, I. V. Shchemerov, A. A. Romanov, A. Kuznetsov, S. J. Pearton
Summary: Ion beam fabrication of metastable polymorphs of Ga2O3, assisted by the controllable accumulation of the disorder in the lattice, is explored for its alternative approach to conventional deposition techniques. In this study, two strategies - ion implantation of silicon donors and plasma treatment with hydrogen - are investigated for tuning the electron concentration in the ion beam created metastable kappa-polymorph. The results show that silicon doping did not change the high resistive state, while hydrogen plasma treatment converted the ion beam fabricated kappa-polymorph to n-type conductivity.
JOURNAL OF APPLIED PHYSICS
(2023)
Editorial Material
Materials Science, Multidisciplinary
Andrej Kuznetsov, Wisanu Pecharapa
PHYSICA STATUS SOLIDI A-APPLICATIONS AND MATERIALS SCIENCE
(2023)
Article
Engineering, Electrical & Electronic
Giovanni Alfieri, Yusuke Fujii, Ruggero Micheletto
Summary: Opto-electronic properties of semiconductors can be altered by impurities and their complexes with intrinsic point defects, such as vacancies. Helium is one such impurity that is incorporated into gallium nitride (GaN) for various technological purposes. However, its electrical activity in GaN and its impact on dopants are not known. In this study, a density functional theory was used to investigate the behavior of substitutional helium and its complexes in wurtzite GaN. It was found that helium is unstable at nitrogen sites and forms nitrogen vacancies, leading to the creation of donor states close to the valence band edge. On the other hand, the presence of a gallium vacancy leads to the formation of an energetically stable complex that generates acceptor states close to the conduction band edge. These findings provide insights into the behavior of helium in GaN and its potential implications for device isolation.
SEMICONDUCTOR SCIENCE AND TECHNOLOGY
(2023)
Article
Chemistry, Multidisciplinary
Emily E. Moore, Timothy P. Genda, Enrica Balboni, Zurong Dai, Aurelien Perron, Kimberly B. Knight
Summary: In a ground-interacting nuclear explosion, the composition and texture of the resulting melt can provide insights into the early cooling conditions of these events. This study uses the CALPHAD method to predict temperature and composition ranges where stable liquid immiscibility might occur in nuclear fallout glass. It also explores the sensitivity of immiscibility to the presence of certain elements and introduces partition coefficients to understand the distribution of components in the melt.
APPLIED SCIENCES-BASEL
(2023)
Article
Chemistry, Multidisciplinary
Per Soderlind, Alexander Landa, Emily E. Moore, Aurelien Perron, John Roehling, Joseph T. McKeown
Summary: In this study, high-temperature thermodynamic properties of gamma-phase uranium were investigated using first-principles, relativistic, and anharmonic theory. The proposed methodology, which includes density-functional theory (DFT) with spin-orbit coupling and self-consistent orbital-polarization (OP) mechanism, provides a more accurate treatment of magnetism and modeling of anharmonic lattice vibrations. The results were compared to CALPHAD modeling, other ab initio methods, and experimental data, showing that the all-electron DFT approach in combination with OP and SCAILD produces Gibbs free energy and heat capacity that are in good agreement with CALPHAD and experimental results, with significant thermal dependence due to the electronic contribution.
APPLIED SCIENCES-BASEL
(2023)
Article
Chemistry, Physical
Kate L. M. Elder, Joel Berry, Aurelien Perron, Brandon Bocklund, Jibril Shittu, Connor J. Rietema, Hunter B. Henderson, Scott K. McCall, Joseph T. McKeown
Summary: The discovery of refractory multi-principal element alloys (MPEAs) with high-temperature strength and stability is achieved by exploring all 165 ternary systems in the Al-Ce-Fe-Hf-Mo-Nb-Ta-Ti-V-W-Zr family. A subset of ternary systems with high strength and robust BCC phase stability is found, and twelve sets of high-performing alloys are identified. Preliminary mechanical tests support the feasibility of this method, which highlights the importance of phase stability, non-equiatomic composition regions, and application-relevant constraints.
NPJ COMPUTATIONAL MATERIALS
(2023)
Article
Chemistry, Physical
Kate L. M. Elder, Joel Berry, Brandon Bocklund, Scott K. McCall, Aurelien Perron, Joseph T. McKeown
Summary: In this study, a computational exploration of the Al-Cr-Fe-Hf-Mo-Nb-Ta-Ti-V-W-Zr compositional space with 11 elements was conducted to identify refractory multi-principal element alloys (MPEAs) with high yield strength and body-centered cubic (BCC) solid solution stability. The findings suggest that medium entropy ternary alloys can outperform alloys with more elements, and highlight the importance of exploring regions away from the equiatomic center of composition space.
NPJ COMPUTATIONAL MATERIALS
(2023)
Article
Chemistry, Physical
Viswanath Pasumarthi, Henry Yu, Sneha A. Akhade, Frank Abild-Pedersen, Joel B. Varley, Michal Bajdich
Summary: Solvation models are important for understanding electrochemical reactions. This study developed a framework to evaluate the effects of potential and electrical double layer on CO reduction. Different solvation models were compared and good agreement was found for intermediate products. This framework can be used to predict optimal electrochemical conditions for specific applications.
JOURNAL OF PHYSICAL CHEMISTRY C
(2023)
Article
Engineering, Manufacturing
Xueqin Huang, Joel Berry, Aurelien Perron, Raymundo Arroyave
Summary: The microstructures formed during rapid solidification in the melt pool have a significant impact on the properties and performance of additively manufactured metals. Predictive simulations of rapid solidification microstructures using phase field models can provide insight into the underlying materials phenomena and offer an alternative to expensive and time-consuming physical experiments. This study compares three phase field models and evaluates their performance in predicting primary dendrite arm spacing, partition coefficient, and transition velocity between different growth modes during rapid solidification.
ADDITIVE MANUFACTURING
(2023)
Article
Engineering, Manufacturing
Saad A. Khairallah, Eric B. Chin, Michael J. Juhasz, Alan L. Dayton, Arlie Capps, Paul H. Tsuji, Kaila M. Bertsch, Aurelien Perron, Scott K. Mccall, Joseph T. Mckeown
Summary: Metal additive manufacturing technologies are receiving significant attention and there is a strong demand to develop methods that link the process science to printed parts performance and overcome inherent limitations. A high-fidelity model based on the multiphysics ALE3D code was developed to replicate the directed energy deposition process at the powder scale and capture the effect of powder incorporation process and flow rate on porosity. The model also explored the use of a ring laser beam profile to improve the solidification microstructure.
ADDITIVE MANUFACTURING
(2023)
Article
Environmental Sciences
Samriti, Marina Rumyantseva, Shuhui Sun, Andrej Kuznetsov, Jai Prakash
Summary: This paper discusses the research on the detection and removal of air pollutants using novel multifunctional nanomaterials. These emerging nano materials have high stability, sensitivity down to parts per-billion level, and excellent removal efficiency for air pollutants. The focus is on their specific strategies and recent highlights in environmental and health monitoring. The challenges and future prospects are also discussed.
CURRENT OPINION IN ENVIRONMENTAL SCIENCE & HEALTH
(2023)