Article
Physics, Applied
Zbigniew Galazka
Summary: This Tutorial provides a detailed description of the critical aspects of bulk beta-Ga2O3 single crystal growth using the Czochralski method. It covers the thermodynamics of Ga2O3, comprehensive solutions for crystal size scale-up, the impact of free carrier absorption on growth stability, and important factors such as crystal growth direction and intentional doping. The resulting crystals' structural quality and basic physical properties are also discussed.
JOURNAL OF APPLIED PHYSICS
(2022)
Article
Thermodynamics
Sobhan Erfantalab, Giacinta Parish, Adrian Keating
Summary: The thermal transport properties of low thermal conductivity porous silicon thin films attached to high thermal conductivity silicon substrates were studied using the 3 omega method. The extracted thermal properties showed a reduction in thermal conductivity and diffusivity as the porosity of the films increased. After passivation, the films exhibited higher values of thermal conductivity and diffusivity. The ability to extract both thermal conductivity and thermal diffusivity for these films removes the need to make assumptions around specific heat capacity.
INTERNATIONAL JOURNAL OF HEAT AND MASS TRANSFER
(2022)
Article
Forestry
Kei Maeda, Yuko Tsunetsugu, Kohta Miyamoto, Tatsuya Shibusawa
Summary: The hot-disk method is a transient method used for measuring thermal properties, and this study found that the thermal properties of wood obtained by this method differed from those obtained by the steady-state method depending on the calculation approach used.
JOURNAL OF WOOD SCIENCE
(2021)
Article
Thermodynamics
Hubert Langevin, Nicolo Giordano, Jasmin Raymond, Louis Gosselin
Summary: An apparatus and analytical approach were developed to assess thermal conductivity and thermal diffusivity in shallow unconsolidated deposits using an oscillatory thermal response test (O-TRT). After validation through numerical modeling, the results demonstrate that the analytical approach, with the use of correction factors, can accurately estimate thermal conductivity and thermal diffusivity with an accuracy of less than 2%. This study shows that O-TRTs are a valuable method for estimating thermal conductivity and thermal diffusivity.
INTERNATIONAL JOURNAL OF HEAT AND MASS TRANSFER
(2023)
Article
Nanoscience & Nanotechnology
M. M. Groz, A. Sommier, E. Abisset-Chavanne, J. C. Batsale, C. Pradere
Summary: A method based on Bayesian inference is proposed in this paper to jointly estimate two fields of thermophysical parameters, the thermal characteristic time and the Biot number. This method is robust to noise, leads to accurate estimations, and is faster and less time-consuming than traditional methods.
Article
Chemistry, Physical
Huijuan Wu, Suiting Ning, Xiangbin Chen, Tian Yu, Tingdong Zhang, Xiang Qu, Ning Qi, Zhiquan Chen
Summary: Multiple strategies were employed to suppress the lattice thermal conductivity in beta-Ga2O3, including the introduction of point defects, grain boundaries, secondary phases, and pores. As a result, the as-sintered beta-Ga2O3 exhibited an extremely low thermal conductivity, attributed to the presence of micro-pores, vacancies, and a high porosity.
ACS APPLIED ENERGY MATERIALS
(2022)
Article
Thermodynamics
Guang Yang, Bing-Yang Cao
Summary: This article introduces a new method for accurately measuring the isotropic or anisotropic thermal conductivity of solid materials using three sensor groups and the Intersection Method. By eliminating errors introduced by the uncertainties of thermal resistance, this method provides a comprehensive and versatile solution.
INTERNATIONAL JOURNAL OF HEAT AND MASS TRANSFER
(2024)
Article
Materials Science, Multidisciplinary
Stefan Marinkovic, Edoardo Trabaldo, Simon Collienne, Floriana Lombardi, Thilo Bauch, Alejandro V. Silhanek
Summary: We conducted experiments on the displacement of oxygen vacancies at high current densities in YBa2Cu3O7-delta films grown on MgO substrates. Our findings indicate that the onset of vacancy migration is determined by local temperature rather than activation energy. We also observed an intermediate phase characterized by a decrease in resistivity before long-range migration of vacancies.
Article
Chemistry, Multidisciplinary
Jinshan Wei, Yuzhe Bu, Qinglin Sai, Hongji Qi, Jingbo Li, Huaimin Gu
Summary: In order to improve the n-type conductivity of single-crystal substrates, Sn element was intentionally added into β-Ga2O3 crystals as n-type dopants. However, it was found that the color of β-Ga2O3 crystal changed significantly after high-temperature remelting in the edge-defined film-fed growth (EFG) method. The carrier concentration in the colorless region was lower than that in the blue region, leading to a decrease in electrical conductivity after high-temperature remelting of Sn-doped β-Ga2O3.
Article
Thermodynamics
Gavin White, Alastair Hales, Yatish Patel, Gregory Offer
Summary: Thermal conductivity is a fundamental parameter in battery pack models, but current measurement methods have large errors. This paper presents three novel methods for measuring thermal conductivity and thermal diffusivity with an accuracy of 5.6%. These methods, designed for materials like lithium-ion batteries, maintain a symmetrical thermal boundary condition around the middle of the cell, leading to improved measurement accuracy. These methods represent the future for thermal characterization of lithium-ion batteries.
APPLIED THERMAL ENGINEERING
(2022)
Article
Thermodynamics
Yuki Sekimoto, Ryo Abe, Hirotaka Kojima, Hiroaki Benten, Masakazu Nakamura
Summary: Accurate thermal conductivity measurement is crucial for designing microscale thermoelectric and heat transfer devices. The 3 omega method is one of the best methods for measuring conductive wires, as it directly measures thermal conductivity without the need for measuring density or specific heat. However, previous studies did not adequately consider the effects of ambient pressure and conductive adhesive, which could affect the accuracy of measurement. This study investigated the influence of ambient pressure and the length of conductive adhesive on the 3 omega method, providing guidelines for more accurate determination of thermal conductivity.
JOURNAL OF THERMAL ANALYSIS AND CALORIMETRY
(2023)
Article
Instruments & Instrumentation
Yulin Chen, You Lv, Xinyue Jiang, Haotian Huang, Yuan Zhu
Summary: The FFT & Aring;ngstrom method utilizes multi-frequency superimposed input signals and FFT for frequency division analysis, which shortens the testing time and enhances the testing robustness of thermal conductivity. It shows good feasibility and robustness compared to the single feeding strategy.
REVIEW OF SCIENTIFIC INSTRUMENTS
(2023)
Article
Thermodynamics
Akos Lakatos, Attila Csik, Istvan Csarnovics
Summary: This paper presents research results on the performance of aerogel materials in terms of thermal conductivity, specific heat, and combustion heat, providing important references for designers and researchers. The study found that temperature and external load significantly affect thermal conductivity, while thickness variations have minor impacts. Additionally, the combustion heat of aerogel was measured and investigated before and after combustion using advanced microscopy techniques.
CASE STUDIES IN THERMAL ENGINEERING
(2021)
Article
Nanoscience & Nanotechnology
Constance Schmidt, Mahfujur Rahaman, Dietrich R. T. Zahn
Summary: In this study, we demonstrate the conversion of GaSe to quasi two-dimensional (2D) beta-Ga2O3 through thermal annealing. Characterization of the annealed samples using Raman spectroscopy and atomic force microscopy revealed the formation of beta-Ga2O3 at temperatures above 600 degrees C, with complete evaporation of Se at temperatures higher than 700 degrees C. The resulting beta-Ga2O3 flakes have half the thickness of the initial GaSe flakes.
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
Physics, Applied
Zbigniew Galazka
Summary: This Tutorial provides a detailed description of the critical aspects of bulk beta-Ga2O3 single crystal growth using the Czochralski method. It covers the thermodynamics of Ga2O3, comprehensive solutions for crystal size scale-up, the impact of free carrier absorption on growth stability, and important factors such as crystal growth direction and intentional doping. The resulting crystals' structural quality and basic physical properties are also discussed.
JOURNAL OF APPLIED PHYSICS
(2022)
Article
Physics, Applied
Zbigniew Galazka, Steffen Ganschow, Palvan Seyidov, Klaus Irmscher, Mike Pietsch, Ta-Shun Chou, Saud Bin Anooz, Raimund Grueneberg, Andreas Popp, Andrea Dittmar, Albert Kwasniewski, Manuela Suendermann, Detlef Klimm, Thomas Straubinger, Thomas Schroeder, Matthias Bickermann
Summary: Two inch diameter highly conducting (Si-doped) beta-Ga2O3 single crystals with high structural quality and surface smoothness were grown by the Czochralski method, making them suitable substrates for homoepitaxy and electronic device fabrication.
APPLIED PHYSICS LETTERS
(2022)
Article
Instruments & Instrumentation
E. Celi, Z. Galazka, M. Laubenstein, S. Nagorny, L. Pagnanini, S. Pirro, A. Puiu
Summary: The paper proposes using a cryogenic calorimeter based on an In2O3 crystal for high-precision measurement of the beta-decay energy spectrum, and discusses the preliminary test results and future improvements.
NUCLEAR INSTRUMENTS & METHODS IN PHYSICS RESEARCH SECTION A-ACCELERATORS SPECTROMETERS DETECTORS AND ASSOCIATED EQUIPMENT
(2022)
Article
Materials Science, Multidisciplinary
Johannes Boy, Ruediger Mitdank, Zbigniew Galazka, Saskia F. Fischer
Summary: This study provides the first experimental determination of the low-temperature thermal properties of novel highly pure single-crystalline ZnGa2O4. It was found that the thermal conductivity increases with decreasing temperatures due to reduced phonon-phonon Umklapp scattering down to 50 K, while at lower temperatures, the thermal conductivity is limited by boundary scattering.
MATERIALS RESEARCH EXPRESS
(2022)
Article
Materials Science, Multidisciplinary
Benjamin M. Janzen, Roland Gillen, Zbigniew Galazka, Janina Maultzsch, Markus R. Wagner
Summary: This study investigates the first- and second-order Raman modes of monoclinic beta-Ga2O3 through a combined experimental-theoretical approach. The phonon frequencies of beta-Ga2O3 are determined through polarized micro-Raman spectroscopy measurements on single crystals. By utilizing density functional perturbation theory and group-theoretical analysis, the mode frequencies, phonon dispersion relation, and phonon density of states are calculated and correlated with experimental results. This study also demonstrates the simultaneous determination of Raman, IR, and acoustic phonons in beta-Ga2O3 using second-order Raman spectroscopy.
PHYSICAL REVIEW MATERIALS
(2022)
Article
Chemistry, Multidisciplinary
Ming-Hsun Lee, Ta-Shun Chou, S. Bin Anooz, Zbigniew Galazka, Andreas Popp, Rebecca L. Peterson
Summary: In this study, we demonstrate a significant improvement in Ti/Au ohmic contact performance by utilizing the anisotropic nature of ??-Ga2O3. Through comprehensive electrical and material characterization of Ti/Au metallization on different semiconductor orientations, we provide direct evidence and insights into the dependence of device performance on the atomic-scale structural anisotropy of ??-Ga2O3.
Article
Physics, Applied
Ta-Shun Chou, Saud Bin Anooz, Raimund Grueneberg, Natasha Dropka, Jana Rehm, Thi Thuy Vi Tran, Klaus Irmscher, Palvan Seyidov, Wolfram Miller, Zbigniew Galazka, Martin Albrecht, Andreas Popp
Summary: (English Summary:)
This study proposes a Langmuir adsorption model for the Si incorporation mechanism into (100) beta-Ga2O3 thin films grown by metalorganic vapor-phase epitaxy, based on the competitive surface adsorption process between Si and Ga atoms. The model describes the major features of the doping process and shows a growth rate-dependent doping behavior, which is experimentally validated and further generalized to different growth conditions and substrate orientations.
APPLIED PHYSICS LETTERS
(2022)
Article
Physics, Applied
Jana Rehm, Ta-Shun Chou, Saud Bin Anooz, Palvan Seyidov, Andreas Fiedler, Zbigniew Galazka, Andreas Popp
Summary: This study provides an overview of the applications of MOVPE-grown (100) beta-Ga2O3 thin films in high-power electronics and discusses the challenges faced. Through analyzing the structural defect formation mechanism, substrate treatment strategies, and growth windows, the grown film was optimized to meet the requirements for device fabrication. Furthermore, this study proposes strategies for future growth process optimization.
APPLIED PHYSICS LETTERS
(2022)
Article
Physics, Applied
Ta-Shun Chou, Palvan Seyidov, Saud Bin Anooz, Raimund Grueneberg, Mike Pietsch, Jana Rehm, Thi Thuy Vi Tran, Kornelius Tetzner, Zbigniew Galazka, Martin Albrecht, Klaus Irmscher, Andreas Fiedler, Andreas Popp
Summary: This study investigated the MOVPE of (100) beta-Ga2O3 films for high-power electronic devices. A height-adjustable showerhead close to the susceptor was crucial in increasing the stability of the Ga wetting layer on the surface and reducing parasitic particles. The achieved film thickness was up to 3 μm with a low root mean square value, and record carrier mobilities were observed at room temperature.
APPLIED PHYSICS LETTERS
(2023)
Article
Crystallography
Detlef Klimm, Binderiya Amgalan, Steffen Ganschow, Albert Kwasniewski, Zbigniew Galazka, Matthias Bickermann
Summary: This paper presents laser flash measurements of the thermal conductivity of Czochralski-grown beta-Ga2O3 single crystals along different crystallographic lattice planes. The results show that the thermal conductivity has orientation dependence and varies with temperature.
CRYSTAL RESEARCH AND TECHNOLOGY
(2023)
Article
Physics, Applied
Ta-Shun Chou, Palvan Seyidov, Saud Bin Anooz, Raimund Grueneberg, Jana Rehm, Tran Thi Thuy Vi, Andreas Fiedler, Kornelius Tetzner, Zbigniew Galazka, Martin Albrecht, Andreas Popp
Summary: In this study, the development of unwanted parasitic particles in the MOVPE chamber during the growth of mu m level films is comprehensively investigated. The density of parasitic particles is observed to be significant at film thicknesses starting from >1.5 to 2 mu m. These particles induce structural defects, such as twin lamellae, which adversely affect the electrical properties of the grown film. The parasitic particles originate from parasitic reactions within the chamber triggered by the promoted gas-phase reactions during the growth process, and their density can be reduced by increasing total gas flow and reducing the showerhead distance to the susceptor. After minimizing the density of parasitic particles, film thicknesses up to 4 mu m have been achieved. RT Hall measurements reveal carrier mobilities of 160 cm(2)V(-1)s(-1) at carrier concentrations of 5.7 x 10(16) cm(-3).
JAPANESE JOURNAL OF APPLIED PHYSICS
(2023)
Article
Physics, Applied
Zbigniew Galazka, Andreas Fiedler, Andreas Popp, Steffen Ganschow, Albert Kwasniewski, Palvan Seyidov, Mike Pietsch, Andrea Dittmar, Saud Bin Anooz, Klaus Irmscher, Manuela Suendermann, Detlef Klimm, Ta-Shun Chou, Jana Rehm, Thomas Schroeder, Matthias Bickermann
Summary: We studied the growth and physical properties of β-(AlxGa1-x)(2)O-3 single crystals with different Al contents using the Czochralski method. The Al segregation coefficient in the Ga2O3 melt resulted in higher Al content in the crystals. By co-doping with Si or Mg, we obtained semiconducting, degenerately semiconducting, or semi-insulating crystals. The lattice constants decreased anisotropically, while the optical bandgap increased linearly with Al content.
JOURNAL OF APPLIED PHYSICS
(2023)
Article
Crystallography
Ta-Shun Chou, Saud Bin Anooz, Raimund Grueneberg, Thuy Vi Thi Tran, Jana Rehm, Zbigniew Galazka, Andreas Popp
Summary: Si-doped beta-Ga2O3 layers were grown on (100) beta-Ga2O3 semi-insulating substrates by MOVPE, and their reflection spectrum on the substrate surface was investigated. Transforming the reflectance spectrum into the autocorrelation domain revealed a more pronounced Fabry-Pe 'rot oscillation, which allowed for easy estimation of the growth rate and growth mode based on the period and damping behavior of the spectrum. The observed oscillation contributed to the refractive index difference between the substrate and the film caused by impurities and preparation techniques. The high sensitivity of reflectance spectroscopy demonstrated its advantage as a powerful growth process monitoring tool.
JOURNAL OF CRYSTAL GROWTH
(2023)
Article
Physics, Applied
Kornelius Tetzner, Michael Klupsch, Andreas Popp, Saud Bin Anooz, Ta-Shun Chou, Zbigniew Galazka, Karina Ickert, Mathias Matalla, Ralph-Stephan Unger, Eldad Bahat Treidel, Mihaela Wolf, Achim Trampert, Joachim Wuerfl, Oliver Hilt
Summary: In this work, vertical (100) beta-Ga2O3 FinFET devices were realized for power electronics applications. The devices were fabricated on highly conducting (100) beta-Ga2O3 substrates and epitaxially grown layers with specific doping concentrations for the drift and channel regions. The fabricated FinFET devices showed enhancement-mode properties and measured breakdown strength.
JAPANESE JOURNAL OF APPLIED PHYSICS
(2023)
Article
Materials Science, Multidisciplinary
Wahib Aggoune, Alberto Eljarrat, Dmitrii Nabok, Klaus Irmscher, Martina Zupancic, Zbigniew Galazka, Martin Albrecht, Christoph Koch, Claudia Draxl
Summary: The perovskite barium stannate (BaSnO3) shows promise for electronic applications due to its transparency and high room-temperature mobility. A combined theoretical and experimental study provides a consistent picture of its electronic structure and optical excitations.
COMMUNICATIONS MATERIALS
(2022)
