Article
Thermodynamics
Xuanhui Fan, Zhongyin Zhang, Jie Zhu, Kunpeng Yuan, Jing Zhou, Xiaoliang Zhang, Dawei Tang
Summary: This study investigated the thermal transport properties of doped silicon using a femtosecond-laser time-domain thermoreflectance method. The results showed that heavily doped silicon had a 22% decrease in thermal conductivity compared to pure silicon. Theoretical calculations and measurements were used to analyze the factors affecting thermal transport in doped silicon. Additionally, measurements were conducted at low temperatures to determine the thermal conductivity of doped silicon samples and the interfacial thermal conductance between silicon and aluminum thin films. These systematic studies provide insights into microscale thermal transport and have implications for industrial applications of doped semiconductors.
INTERNATIONAL JOURNAL OF THERMAL SCIENCES
(2022)
Article
Materials Science, Multidisciplinary
Z. Cheng, W. Lu, J. Shi, D. Tanaka, N. H. Protik, S. Wang, M. Iwaya, T. Takeuchi, S. Kamiyama, I. Akasaki, H. Amano, S. Graham
Summary: This study investigated the temperature-dependent thermal conductivity of doped epitaxial 6H-SiC and monocrystalline porous 6H-SiC below room temperature using time-domain thermoreflectance, revealing strong quasi-ballistic thermal transport. Doping and structural boundaries were applied to tune the quasi-ballistic thermal transport, with observations on the selective scattering effects of nitrogen and boron dopants on phonon transport.
MATERIALS TODAY PHYSICS
(2021)
Article
Materials Science, Multidisciplinary
Zhongyin Zhang, Xuanhui Fan, Jie Zhu, Kunpeng Yuan, Jing Zhou, Dawei Tang
Summary: High-pressure is widely used to improve material performances, such as thermal conductivity and interfacial thermal conductance. Gallium arsenide (GaAs) has attracted extensive attention in high-pressure studies due to its technological importance and complex structure transitions. The thermal properties of GaAs under high pressure are still not well understood. In this study, we systematically investigate GaAs and G Al/GaAs under multi-structure up to approximately 23 GPa. Our findings provide insights into understanding the role of phonons, lattice defects, and electrons in GaAs under pressure, as well as the enhancement of thermal conductance in G Al/GaAs.
JOURNAL OF MATERIALS SCIENCE & TECHNOLOGY
(2023)
Article
Materials Science, Multidisciplinary
Xuanhui Fan, Zhongyin Zhang, Jing Zhou, Kunpeng Yuan, Jie Zhu, Dawei Tang
Summary: In this study, the anisotropic thermal properties of ZnO crystal under 0-20 GPa pressure were characterized using a combination of the time-domain thermoreflectance technique and diamond anvil cell. The micro-structure of ZnO in the same pressure range was also studied by Raman spectra. The experimental results and theoretical analysis advance the understanding of the thermal transport mechanism of wide-gap semiconductors under high pressure.
JOURNAL OF MATERIALS RESEARCH AND TECHNOLOGY-JMR&T
(2023)
Article
Chemistry, Multidisciplinary
Lin Jing, Rui Cheng, Muzzafer Tasoglu, Zexiao Wang, Qixian Wang, Hannah Zhai, Sheng Shen
Summary: This article introduces a novel sandwich-structured thermal interface material with a record-low thermal resistance and high flexibility. It combines vertically aligned copper nanowires and a graphene coating to achieve efficient thermal management in modern electronics.
Article
Physics, Multidisciplinary
Qing-Jian Lu, Min Gao, Chang Lu, Fei Long, Tai-Song Pan, Yuan Lin
Summary: Vanadium dioxide (VO2) is a strongly correlated material known for its sharp metal-insulator transition (MIT) near room temperature. The thermal conductivity change rates across MIT of VO2 thin films are found to be correlated with the electrical conductivity change rate, possibly due to the increasing elastic electron scattering weight caused by defects in the film. The study demonstrates the feasibility and limitation of investigating the thermal properties of VO2 thin films using the TDTR method without depositing any metal thermoreflectance layer.
Article
Metallurgy & Metallurgical Engineering
Zhou Lijun, Wei Song, Guo Jingdong, Sun Fangyuan, Wang Xinwei, Tang Dawei
Summary: This study proposes a novel method based on femtosecond laser to quantitatively measure the thermophysical parameters of Cu-Sn IMCs. The thermal conductivities of Cu6Sn5 and Cu3Sn were determined and the parameters affecting the measurement accuracy were analyzed.
ACTA METALLURGICA SINICA
(2022)
Article
Chemistry, Multidisciplinary
Ethan A. Scott, Sean W. King, Nanette N. Jarenwattananon, William A. Lanford, Han Li, James Rhodes, Patrick E. Hopkins
Summary: The thermal conductivity of amorphous solids can be increased through ion irradiation, altering the bonding network configuration. Films with higher initial hydrogen content show the greatest enhancement, accompanied by stiffening and densification from the irradiation process. This enhancement in vibrational transport is unique compared to the structural degradation and reduced thermal conductivity typically seen in ion conductivities of crystalline materials.
Article
Chemistry, Physical
Hyunwoo Bark, Matthew Wei Ming Tan, Gurunathan Thangavel, Pooi See Lee
Summary: This study introduces a strategy to obtain thermally conductive and soft elastomers with a high-volume ratio of EGaIn nanoparticles by surface modification and crosslinking, demonstrating excellent thermal transport properties and low elastic modulus. The elastomer exhibits anisotropic thermal conductivity upon stretching, making it suitable for use as a thermal interface layer for thermoelectric devices.
ADVANCED ENERGY MATERIALS
(2021)
Article
Multidisciplinary Sciences
Sien Wang, Yue Xiao, Qiyu Chen, Qing Hao
Summary: Nanoporous Si films have potential applications in thermoelectrics and thermal management of devices. Offset nanoslot patterns achieve smaller characteristic lengths and lower thermal conductivity compared to periodic circular pores. Additional reduction in thermal conductivity can be achieved by implanting Ga ions.
Article
Engineering, Electrical & Electronic
Mohammadreza Shahzadeh, Olga Andriyevska, Ruslan Salikhov, Lorenzo Fallarino, Olav Hellwig, Simone Pisana
Summary: Research has shown limitations in traditional diffusive theories for heat transport across high-density metallic interfaces. By systematically studying Pt/Co multilayers using frequency domain thermoreflectance, it is possible to measure the anisotropic thermal conductivity of the multilayers and investigate the effect of interface density on the effective thermal conductivity of the multilayers.
ACS APPLIED ELECTRONIC MATERIALS
(2021)
Article
Chemistry, Multidisciplinary
Heungdong Kwon, Asir Intisar Khan, Christopher Perez, Mehdi Asheghi, Eric Pop, Kenneth E. Goodson
Summary: The research investigates the electrical and thermal transport properties of superlattice-like phase change memory based on Sb2Te3 and GeTe, revealing interface resistances, coherence transition of phonon transport, and strong anisotropy in electrical resistivity due to weakly interacting van der Waals-like gaps.
Article
Chemistry, Multidisciplinary
Hongyao Xie, Emil S. Bozin, Zhi Li, Milinda Abeykoon, Soham Banerjee, James P. Male, G. Jeffrey Snyder, Christopher Wolverton, Simon J. L. Billinge, Mercouri G. Kanatzidis
Summary: This study reports the phenomenon of local symmetry breaking in the compound AgGaTe2, which explains the unexpectedly low thermal conductivities of silver-based compounds compared to copper-based analogs. It provides a guideline to suppress heat transport in diamondoid and other materials.
ADVANCED MATERIALS
(2022)
Article
Chemistry, Multidisciplinary
Debattam Sarkar, Kapildeb Dolui, Vaishali Taneja, Abdul Ahad, Moinak Dutta, S. O. Manjunatha, Diptikanta Swain, Kanishka Biswas
Summary: This study reports the synthesis of a new p-type cubic AgSnSbTe3 crystal, which exhibits an inherently ultra-low lattice thermal conductivity and high electrical conductivity. The softening of the lattice in AgSnSbTe3 is attributed to the generation of antibonding states due to the interaction between Sn(5s)/Ag(4d) and Te(5p) orbitals. Additionally, the compound shows metavalent bonding, which provides highly polarizable bonds with strong lattice anharmonicity while maintaining superior electrical conductivity. The electronic band structure with nearly degenerate valence-band maxima contributes to achieving a high Seebeck coefficient throughout the measured temperature range, leading to a maximum thermoelectric figure of merit of 1.2 at 661 K in the pristine single crystal of AgSnSbTe3.
ANGEWANDTE CHEMIE-INTERNATIONAL EDITION
(2023)
Article
Chemistry, Physical
Youngshang Han, Leif-Erik Simonsen, Mohammad H. Malakooti
Summary: This study introduces highly efficient, stretchable thermoelectric generators made of inorganic semiconductors and printed multifunctional soft matter. The thermoelectric generators are able to conform to curved surfaces and maintain efficiency under large deformations, while also exhibiting durability. The generators generate high open-circuit voltage and power density, and can withstand stretching cycles at high strain. The use of liquid metal elastomer composites and elastomer composites with hollow microspheres contribute to the performance and durability of the generators.
ADVANCED ENERGY MATERIALS
(2022)
Article
Materials Science, Multidisciplinary
Eunwook Jeong, Eun-Ae Choi, Yoshifumi Ikoma, Seung Min Yu, Jong-Seong Bae, Sang-Geul Lee, Seung Zeon Han, Gun-Hwan Lee, Jungheum Yun
Summary: Utilizing oxidation-induced clustering and layering can promote the evolution of gold clusters and layers, making them highly wetted on their oxide supports.
Article
Metallurgy & Metallurgical Engineering
Y. Shigeta, M. Aramaki, K. Ashizuka, Y. Ikoma, Y. Ozaki
Summary: This study investigated the effect of a Cu-rich networked phase on the yield strength of powder metallurgy steel. The results showed that the maximum values of 0.2% proof stress and ultimate tensile strength were achieved at x = 0.68, where a high-density compact with well-networked Cu-rich ferrite phase was developed without Cu growth. Additionally, nanosized epsilon-Cu precipitates were observed in the Cu-rich ferrite, contributing to the precipitation strengthening in the network.
Article
Chemistry, Physical
Eunwook Jeong, Yoshifumi Ikoma, Seung Min Yu, Jong-Seong Bae, Sang-Geul Lee, Seung Zeon Han, Gun-Hwan Lee, Weon-Sik Chae, Eun-Ae Choi, Jungheum Yun
Summary: The study suggests that incorporating excessive atomic O at ZnO surfaces enhances adhesion between Au and ZnO, facilitating high nucleation densities of Au nanoparticles with reduced diameters. This is contrary to current beliefs and emphasizes the crucial role played by atomic O in enhancing the adhesion of Au with oxides and developing unique structural features of Au nanoparticles.
APPLIED SURFACE SCIENCE
(2021)
Article
Physics, Applied
Cheng Shao, Kensuke Matsuda, Shenghong Ju, Yoshifumi Ikoma, Masamichi Kohno, Junichiro Shiomi
Summary: Experimental and numerical investigation of phonon transport in multiphase nanostructured silicon synthesized through high-pressure torsion was conducted. The study revealed a weak temperature dependence in thermal conductivity in the temperature range of 150-330K and showed good agreement between predicted thermal conductivity from multiscale modeling and experimental measurements. Additionally, increasing the volume fractions of Si-III and Si-XII phases was suggested to further reduce the effective thermal conductivity of nanostructured silicon from high-pressure torsion.
JOURNAL OF APPLIED PHYSICS
(2021)
Article
Chemistry, Physical
Guoqing Zhao, Eunwook Jeong, Sang-Geul Lee, Seung Min Yu, Jong-Seong Bae, Jongjoo Rha, Gun-Hwan Lee, Yoshifumi Ikoma, Jungheum Yun
Summary: This study presents novel insights into improving the wetting of Ag on oxides using homogeneous Ag wetting seeds. By incorporating minimal dissolved atomic O as a surfactant into Ag nanoparticles, the size and shape of the O-incorporated Ag nanoparticles were precisely controlled to accelerate the wetting transition of Ag on ZnO substrates. These results demonstrate a notable strategy for achieving a rapid Ag wetting transition towards a completely continuous layer with ultralow optoelectrical losses.
APPLIED SURFACE SCIENCE
(2021)
Article
Materials Science, Multidisciplinary
Yoshifumi Ikoma, Terumasa Yamasaki, Takahiro Masuda, Yoshinori Tange, Yuji Higo, Yasuo Ohishi, Martha R. McCartney, David J. Smith, Zenji Horita
Summary: In situ observation using synchrotron X-ray diffraction was conducted to study the phase transformation in Si containing diamond-cubic and metastable phases during annealing. Metastable body-centred-cubic and hexagonal diamond phases were identified at different annealing temperatures, suggesting a phase transformation mainly from bc8 to hd during the process.
PHILOSOPHICAL MAGAZINE LETTERS
(2021)
Article
Materials Science, Multidisciplinary
Eunwook Jeong, Yoshifumi Ikoma, Taehyeong Lee, Hyejin Kim, Seung Min Yu, Sang-Geul Lee, Jong-Seong Bae, Seung Zeon Han, Gun-Hwan Lee, Dooho Choi, Eun-Ae Choi, Jungheum Yun
Summary: This study reports a method for fabricating an ultrathin, highly crystalline, complexly continuous Cu layer mediated by Ge. The segregation of Ge remarkably enhances the wetting of Cu layer on ZnO substrate. The Cu layer fabricated by this method exhibits a record-low optical loss at near-bulk resistivity and exceptional durability in water, ozone, and high-temperature environments.
Review
Materials Science, Multidisciplinary
Kaveh Edalati, Andrea Bachmaier, Victor A. Beloshenko, Yan Beygelzimer, Vladimir D. Blank, Walter J. Botta, Krzysztof Bryla, Jakub Cizek, Sergiy Divinski, Nariman A. Enikeev, Yuri Estrin, Ghader Faraji, Roberto B. Figueiredo, Masayoshi Fuji, Tadahiko Furuta, Thierry Grosdidier, Jeno Gubicza, Anton Hohenwarter, Zenji Horita, Jacques Huot, Yoshifumi Ikoma, Milos Janecek, Megumi Kawasaki, Petr Kral, Shigeru Kuramoto, Terence G. Langdon, Daniel R. Leiva, Valery Levitas, Andrey Mazilkin, Masaki Mito, Hiroyuki Miyamoto, Terukazu Nishizaki, Reinhard Pippan, Vladimir V. Popov, Elena N. Popova, Gencaga Purcek, Oliver Renk, Adam Revesz, Xavier Sauvage, Vaclav Sklenicka, Werner Skrotzki, Boris B. Straumal, Satyam Suwas, Laszlo S. Toth, Nobuhiro Tsuji, Ruslan Z. Valiev, Gerhard Wilde, Michael J. Zehetbauer, Xinkun Zhu
Summary: This article comprehensively reviews recent advances in the development of ultrafine-grained and nanostructured materials through severe plastic deformation and provides a brief history of this field. Severe plastic deformation methods have been effective in producing materials with advanced mechanical and functional properties, and the field of NanoSPD has experienced significant progress in the past two decades.
MATERIALS RESEARCH LETTERS
(2022)
Article
Nanoscience & Nanotechnology
Eunwook Jeong, Taehyeong Lee, Dooho Choi, Seung Min Yu, Sang-Geul Lee, Jong-Seong Bae, Seung Zeon Han, Gun-Hwan Lee, Yoshifumi Ikoma, Eun-Ae Choi, Jungheum Yun
Summary: This study demonstrates the effectiveness of atomic oxygen-mediated growth in synthesizing an ideal Au-layered structure with exceptional optoelectrical performance. The 4-nm-thick, quasi-single-crystalline Au layer exhibits record-low resistivity and minimal optical loss.
ACS APPLIED MATERIALS & INTERFACES
(2022)
Article
Materials Science, Multidisciplinary
Mitsuhiro Muta, Suguru Nishikawa, Ataru Ichinose, Yukio Sato, Makoto Arita, Yoshifumi Ikoma, Masashi Mukaida
Summary: Preferred orientation and optical responses were investigated for BaBiO3 films grown by pulsed laser deposition. The films exhibited monoclinic symmetry I2/m and a (110) preferred orientation. The estimated optical bandgaps were around 2.3 eV for direct transition and 2.1 eV for indirect transition. The decay time of photoconductivity was found to be approximately 0.48 sec. The relationship between ultraviolet light-induced photoconductivity and film crystallinity was clarified, with high-quality crystalline BaBiO3 films exhibiting lower photoconductivity, contrary to TiO2 films.
Article
Physics, Applied
Yoshifumi Ikoma, Kensuke Matsuda, Keigo Yoshida, Marina Takaira, Masamichi Kohno
Summary: We studied the electric, thermal, and optical properties of Si after severe plastic deformation. The processed samples consisted of metastable phases, diamond-cubic Si-I, and amorphous phases. The resistivity of the samples increased and then decreased with increasing the processing times. The thermal conductivity was significantly reduced after processing. Photoluminescence peak from nanograins appeared after annealing. These results suggest that the properties of the processed Si are strongly influenced by the formation of metastable phases and grain refinement.
JOURNAL OF APPLIED PHYSICS
(2022)
Article
Nanoscience & Nanotechnology
Kazutoshi Takahashi, Yuki Umeda, Masaki Imamura, Marina Takaira, Yoshifumi Ikoma, Yasutomo Arai
Summary: The composition and structure of SiGe alloys play a key role in their electronic band structure, allowing for a wide range of applications. This study used high-resolution core-level and angle-resolved photoemission spectroscopy to investigate the surface of unstrained SiGe single crystals. The results showed a double domain reconstruction with an asymmetric dimer composed of Ge atoms and Si atoms located below the subsurface region. Additionally, three-dimensional ARPES measurements using synchrotron radiation revealed the compositional dependence of the valence bands.
Article
Materials Science, Multidisciplinary
Yoshifumi Ikoma
Summary: We investigated the effects of high-pressure torsion (HPT) processing on Si and related semiconducting materials, focusing on their phase transformations and electrical, thermal, and optical properties. The experiments revealed that HPT processing induced phase transformations in Si, resulting in the appearance of metastable phases such as Si-III, Si-XII, and Si-IV. The resistivity of Si decreased after HPT processing, and the thermal conductivity was significantly reduced. In addition, the HPT processing of Si0.5Ge0.5 crystal resulted in the formation of a metastable semimetallic phase, bc8-Si0.5Ge0.5. These findings suggest that HPT processing offers new opportunities for the development of novel devices utilizing nanograins and metastable phases.
MATERIALS TRANSACTIONS
(2023)
Article
Chemistry, Physical
Bin Xu, Yuxuan Liao, Zhenglong Fang, Yifei Li, Rulei Guo, Ryohei Nagahiro, Yoshifumi Ikoma, Masamichi Kohno, Junichiro Shiomi
Summary: By applying a moderate high-pressure torsion (HPT) process on nanocrystalline silicon, the lattice thermal conductivity is further reduced by introducing finer nanostructures and internal strain. This study demonstrates a practical and feasible strain engineering strategy for achieving low thermal conductivity in various nanocrystalline materials.
JOURNAL OF MATERIALS CHEMISTRY A
(2023)
Article
Materials Science, Multidisciplinary
Yoshifumi Ikoma, Terumasa Yamasaki, Takahiro Shimizu, Marina Takaira, Masamichi Kohno, Qixin Guo, Martha R. McCartney, David J. Smith, Yasutomo Arai, Zenji Horita
MATERIALS CHARACTERIZATION
(2020)