Article
Materials Science, Multidisciplinary
Sara Conti, Samira Saberi-Pouya, Andrea Perali, Michele Virgilio, Francois M. Peeters, Alexander R. Hamilton, Giordano Scappucci, David Neilson
Summary: By confining holes in a compressively strained Germanium quantum well and electrons in a lattice-matched tensile strained Silicon quantum well in a lattice-matched strained Si/Ge bilayer embedded into a Germanium-rich SiGe crystal, observable mass-imbalanced electron-hole superfluidity and BEC can be achieved, potentially leading to superfluidity at experimentally accessible temperatures.
NPJ QUANTUM MATERIALS
(2021)
Article
Chemistry, Multidisciplinary
Buqing Xu, Guilei Wang, Yong Du, Yuanhao Miao, Yuanyuan Wu, Zhenzhen Kong, Jiale Su, Ben Li, Jiahan Yu, Henry H. Radamson
Summary: This manuscript investigates the integration of a strained Ge channel with Si-based FinFETs, focusing on high-AR fin structure preparation, appropriate etching topography, and highly compressive strain growth of Ge. The study compared wet etching and in situ dry etching methods for better etching topography, and performed selective epitaxial growth of Ge on a patterned substrate. Results showed benefits in dislocation suppression and pMOS transport characteristics enhancement. The pattern dependency of Ge growth on patterned wafer was measured, discussing solutions for uniform epitaxy.
Article
Materials Science, Multidisciplinary
Tyler Stabile, Yize Stephanie Li
Summary: This study investigates the deposition of strained alpha-Sn thin films on highly lattice-mismatched Ge (100) substrates by physical vapor deposition, using different cleaning methods. The results show that the morphology of thin films is significantly influenced by the cleaning method. It is demonstrated that the alpha-Sn thin films deposited on Ge substrates exhibit n-type electrical properties and may hold potential for advanced electronics and photonics applications.
MATERIALS TODAY ADVANCES
(2021)
Article
Nanoscience & Nanotechnology
M. G. Bartmann, M. Sistani, S. Glassner, B. Salem, T. Baron, P. Gentile, J. Smoliner, A. Lugstein
Summary: In this study, the impact of strain on intrinsic germanium nanowires was investigated, and the analysis was conducted through optical and electrical characterization. Experimental results showed a decrease in resistivity by almost three orders of magnitude at a strain level of approximately 5%. Additionally, we calculated the band gap narrowing of germanium for moderate strain levels.
Article
Multidisciplinary Sciences
Leila Balaghi, Si Shan, Ivan Fotev, Finn Moebus, Rakesh Rana, Tommaso Venanzi, Rene Hubner, Thomas Mikolajick, Harald Schneider, Manfred Helm, Alexej Pashkin, Emmanouil Dimakis
Summary: Semiconductor nanowires have potential for novel transistor concepts with higher electron mobility in strained coaxial nanowire heterostructures than in bulk crystals. Core/shell heterostructures, especially with a thick shell under strain, show significantly enhanced electron mobility compared to unstrained nanowires or bulk crystals, making strained gallium arsenide nanowires a unique candidate for advancing transistor technology.
NATURE COMMUNICATIONS
(2021)
Article
Materials Science, Multidisciplinary
Andrew J. Miller, Will J. Hardy, Dwight R. Luhman, Mitchell Brickson, Andrew Baczewski, Chia -You Liu, Jiun-Yun Li, Michael P. Lilly, Tzu-Ming Lu
Summary: Lithographic quantum dots in strained-Ge/SiGe have rapidly advanced from the realization of a single-hole quantum dot to multiqubit devices. This study presents a measurement of the out-of-plane g factor for a single-hole quantum dot in this material and validates the expected g-factor anisotropy.
Article
Chemistry, Physical
Hui Yan, Meng Zhang, Shuang Wang, Heng Li, Sandor Kunsagi-Mate, Shougen Yin
Summary: Graphene's exceptional mechanical flexibility and strength make it an ideal platform for strain engineering, allowing for versatile modulation and enhancement of its optical properties. By transferring monolayer graphene onto monodisperse Au nanoparticles, both uniaxial and biaxial strain can be achieved with negligible charge doping. This study examines the phonon frequency and crystallographic orientation of graphene wrinkles under strain, showing significant red shifts in the G and 2D peaks under tensile strain.
APPLIED SURFACE SCIENCE
(2023)
Article
Chemistry, Physical
Yong-Lie Sun, Wipakorn Jevasuwan, Naoki Fukata
Summary: Germanium (Ge) nanowire arrays are considered as promising channel materials for high-performance field-effect transistors (FETs) due to their excellent electronic transport properties, silicon (Si) compatibility, and high integration. Highly ordered Ge nanowires with low contamination are produced using nanoimprint lithography (NIL) and Bosch etching. Ge/Si core-shell nanowires are prepared by forming p-Si shells on Ge nanowires, demonstrating good crystalline quality and sharp interfaces. The accumulation of hole gas inside the Ge nanowires is investigated using Raman scattering.
APPLIED SURFACE SCIENCE
(2024)
Article
Chemistry, Physical
Jiarun Geng, Zhuo Zhu, Youxuan Ni, Haixia Li, Fangyi Cheng, Fujun Li, Jun Chen
Summary: Surface strain engineering is an effective strategy to enhance the electrocatalytic properties of noble metal nanocrystals. A dual-phase palladium-copper (DP-PdCu) bimetallic electrocatalyst with remarkable biaxial strain was constructed via a wet-chemical approach, showing superior activity towards formic acid oxidation. Density functional theory calculations revealed the downshift of d-band center of Pd atoms due to interfacial strain, weakening the adsorption strength of undesired intermediates.
Article
Chemistry, Multidisciplinary
Qinghua Zhang, Fanqi Meng, Ang Gao, Xinyan Li, Qiao Jin, Shan Lin, Shengru Chen, Tongtong Shang, Xing Zhang, Haizhong Guo, Can Wang, Kuijuan Jin, Xuefeng Wang, Dong Su, Lin Gu, Er-Jia Guo
Summary: This study investigates the migration pathways of oxygen ions in cobaltites under strain conditions, revealing anisotropic oxygen-ion migration behavior. The research highlights the crucial role of the tolerance factor in the stability of oxygen vacancy channels and establishes a strain-dependent phase diagram. The findings provide valuable insights for engineering the orientation of oxygen vacancy channels in ionic-oxide electronics.
Article
Astronomy & Astrophysics
Alessandro Nagar, Piero Rettegno, Rossella Gamba, Sebastiano Bernuzzi
Summary: Dynamical capture is a formation channel for binary black hole mergers resulting in eccentric dynamics and unique gravitational wave signals, requiring precise predictions and waveform models. A state of the art effective one-body model is presented for such mergers, demonstrating reliable characterization of the parameter space and potential for improving accuracy through further analysis. Numerical-relativity simulations can inform waveform models for present and future gravitational wave detectors.
Article
Nanoscience & Nanotechnology
Qimiao Chen, Liyao Zhang, Yuxin Song, Xiren Chen, Sebastian Koelling, Zhenpu Zhang, Yaoyao Li, Paul M. Koenraad, Jun Shao, Chuan Seng Tan, Shumin Wang, Qian Gong
Summary: Highly tensile-strained Ge quantum dots emitting structures with different sizes were successfully grown on InP substrates by molecular beam epitaxy. The photoluminescence from direct band-gap-like transitions of TS-Ge-QDs was achieved, and the band structure of the TS-Ge-QDs emitting structures was calculated to support the experimental results. These results provide encouraging evidence for the future photonics applications of this promising highly tensile strained semiconductor-nanostructure-based platform such as integrated light sources.
ACS APPLIED NANO MATERIALS
(2021)
Article
Chemistry, Multidisciplinary
Diana Zapata Dominguez, Christopher L. Berhaut, Anton Buzlukov, Michel Bardet, Praveen Kumar, Pierre-Henri Jouneau, Antoine Desrues, Adrien Soloy, Cedric Haon, Nathalie Herlin-Boime, Samuel Tardif, Sandrine Lyonnard, Stephanie Pouget
Summary: Germanium is a promising active material for high energy density anodes in Li-ion batteries, and a deep understanding of its (de)lithiation mechanism requires advanced characterizations. By using operando X-ray diffraction and ex situ Li-7 solid-state NMR, researchers have revealed the structural and chemical evolution of crystalline germanium nanoparticles during charge and discharge cycles. The study shows the reversible lattice strain behavior of crystalline germanium, as well as the formation of amorphous and crystalline lithiated phases.
Article
Optics
Nageswara Lalam, Hari Bhatta, Xiaoguang Sun, Ping Lu, Paul Ohodnicki, Michael p. Buric, Ruishu Wright
Summary: This paper presents a multi-parameter fiber sensing system based on a double-Brillouin peak specialty fiber with enhanced Brillouin gain response. Compared to other multi-Brillouin peak fibers, the proposed fiber significantly reduces measurement errors and improves strain and temperature accuracy. Successful discriminative measurement of strain and temperature is achieved by utilizing the sensitivity values of each Brillouin gain spectrum peak. The double-Brillouin peak fiber can serve as an alternative to other fibers for strain and temperature measurement, eliminating the need for complex monitoring setups and reducing measurement errors. It is highly recommended for long-distance natural gas pipeline monitoring where discriminative strain and temperature measurement is crucial.
Article
Optics
Nageswara Lalam, Hari Bhatta, Xiaoguang Sun, Ping Lu, Paul Ohodnicki, Michael p. Buric, Ruishu Wright
Summary: In this paper, a multi-parameter fiber sensing system based on stimulated Brillouin scattering in a double-Brillouin peak specialty fiber is demonstrated. The system enhances the Brillouin gain response and achieves discriminative measurement of strain and temperature.
Article
Nanoscience & Nanotechnology
Michinobu Fujiwara, Kazuma Takahashi, Yoshihiko Nakagawa, Kazuhiro Gotoh, Takashi Itoh, Yasuyoshi Kurokawa, Noritaka Usami
Summary: The effect of low growth rate deposition (LGD) of BaSi2 on the film quality and performance of silicon heterojunction solar cells was investigated. It was found that LGD improved the crystalline structure and performance of the solar cells, with a maximum conversion efficiency of 10.62%. This improvement is attributed to the rearrangement of atoms during LGD.
Article
Physics, Applied
Haitao Wang, Yasuyoshi Kurokawa, Kazuhiro Gotoh, Shinya Kato, Shigeru Yamada, Takashi Itoh, Noritaka Usami
Summary: Effective strategies for improving the performance of a droplet-based electricity generator (DEG) are proposed, including introducing an intermediate layer of cyclic transparent optical polymer (CYTOP) by adjusting the thickness, injecting ionized ions into the surface, and increasing the surface area. Positive effects of the introduction of a CYTOP layer on outputs, especially with a greater thickness, surface ionized-air modification, and larger surface area, were observed, which could promote the practical application of DEG in energy harvesting.
JAPANESE JOURNAL OF APPLIED PHYSICS
(2023)
Article
Physics, Applied
Takumi Deshimaru, Kenta Yamakoshi, Kentaro Kutsukake, Takuto Kojima, Tsubasa Umehara, Haruhiko Udono, Noritaka Usami
Summary: The growth mechanism of multicrystalline Mg2Si crystal was analyzed using optical reflection image analysis and crystal orientation measurement. It was found that grains with higher surface energy competitively expanded during crystal growth, possibly due to the difference in growth rate caused by high supercooling.
JAPANESE JOURNAL OF APPLIED PHYSICS
(2023)
Article
Physics, Applied
Keisuke Shibata, Shinya Kato, Masashi Kurosawa, Kazuhiro Gotoh, Satoru Miyamoto, Noritaka Usami, Yasuyoshi Kurokawa
Summary: Boron-doped silicon nanocrystals/amorphous silicon oxide multilayers were prepared and their properties were investigated. The electrical conductivity of the multilayers increased with a thickness of the a-SiOx layer and saturated at a certain value. The Seebeck coefficient remained constant and the thermal conductivity was independent of the a-SiOx layer thickness, with a maximum power factor obtained at a specific thickness.
JAPANESE JOURNAL OF APPLIED PHYSICS
(2023)
Article
Materials Science, Multidisciplinary
Hao Luo, Van Hoang Nguyen, Kazuhiro Gotoh, Saya Ajito, Tomohiko Hojo, Yasuyoshi Kurokawa, Eiji Akiyama, Noritaka Usami
Summary: This study investigates the effect of post-oxidizing treatment (POT) on the structural, optical, and passivation performances of titanium oxide coated crystalline Si (c-Si) heterostructures prepared by the solution process. The results show that POT improves the passivation performance by oxidizing the TiOx film, c-Si surface, and forming POx.
Article
Materials Science, Multidisciplinary
H. Kojima, T. Nishihara, K. Gotoh, N. Usami, T. Hara, K. Nakamura, Y. Ohshita, A. Ogura
Summary: We evaluated the damage caused by plasma enhanced chemical vapor deposition (PECVD) of hydrogenated amorphous silicon (a-Si:H) to crystalline silicon (c-Si). The damaged layer on the c-Si surface under the a-Si:H film was measured by lifetime measurements and was approximately 2.8 nm thick. The damage did not disappear even after annealing at 200 degrees C for 30 min in the air atmosphere. Photoluminescence (PL) measurements revealed that the damage was a non-luminescent defect. We found that the difference in H-2 flow rate during a-Si:H deposition affected the depth of damage penetration into c-Si. Our conclusion is that the damage introduced into c-Si during a-Si:H deposition by PECVD is primarily caused by H atoms.
ECS JOURNAL OF SOLID STATE SCIENCE AND TECHNOLOGY
(2023)
Article
Physics, Applied
Shohei Fukaya, Kazuhiro Gotoh, Takuya Matsui, Hitoshi Sai, Yasuyoshi Kurokawa, Noritaka Usami
Summary: In this study, a simple method was proposed to investigate the effect of metallization on the surface passivation of titanium oxide (TiO x )/Si heterostructures. The relationship between implied open-circuit voltage (iV (OC)) and photoluminescence (PL) intensity imaging of solar cell precursors before metallization was studied using PL imaging technique. Based on this relationship, the quantitative evaluation of the change in iV (OC) before and after metallization on the TiO x was performed. The results showed that the iV (OC) predicted by the PL measurement decreased by 23-104 mV after metal deposition and had a good agreement with the measured V (OC) in the finished solar cells. The evaluation of iV (OC) by PL measurement provides a useful prediction of V (OC) after metallization, which helps in analyzing the passivation degradation induced by metallization.
JAPANESE JOURNAL OF APPLIED PHYSICS
(2023)
Article
Physics, Applied
Kazuhiro Gotoh, Ryo Ozaki, Motoo Morimura, Aki Tanaka, Yoshiko Iseki, Kyotaro Nakamura, Kazuo Muramatsu, Yasuyoshi Kurokawa, Yoshio Ohshita, Noritaka Usami
Summary: We investigated the effect of B2H6 plasma treatment on p-type hydrogenated amorphous silicon (p-a-Si:H) surfaces for high-performance silicon heterojunction (SHJ) solar cells. The boron concentration at the p-a-Si:H surface increased after the B2H6 plasma treatment, and the specific contact resistance decreased by about one-third. The power conversion efficiency of SHJ solar cells improved due to increased fill factor (FF) resulting from decreased series resistance and increased shunt resistance, which was attributed to the enhanced upward band bending at the heterointerface between transparent conductive oxide (TCO) and p-a-Si:H caused by the B2H6 plasma treatment.
JAPANESE JOURNAL OF APPLIED PHYSICS
(2023)
Article
Crystallography
T. Keerthivasan, Xin Liu, M. Srinivasan, Noritaka Usami, G. Anbu, G. Aravindan, P. Ramasamy
Summary: Numerical simulations were used to investigate the growth of multicrystalline silicon. By partially replacing the bottom of the susceptor with an insulation block, a better quality and lower power consumption multicrystalline silicon ingot was obtained.
JOURNAL OF CRYSTAL GROWTH
(2023)
Article
Engineering, Electrical & Electronic
Yasuyoshi Kurokawa, Kaisei Sato, Keisuke Shibata, Shinya Kato, Satoru Miyamoto, Kazuhiro Gotoh, Takashi Itoh, Noritaka Usami
Summary: By thermal evaporation of Mg and face-to-face annealing (FTFA), Mg2Si thin films were obtained on a crystalline Si substrate and a P-doped hydrogenated amorphous Si thin films on a quartz substrate. FTFA suppressed Mg evaporation, Mg2Si oxidation, and Mg2Si decomposition, resulting in the formation of polycrystalline Mg2Si thin film with large grain size. The effects of annealing temperature (TA) on crystal structure and thermoelectric properties of Mg2Si thin films were investigated. A relatively high ZT value of 0.68 was achieved at 712 K for a sample prepared at TA = 623 K, attributed to increased electrical conductivity, high Seebeck coefficient of -235 mu V center dot K-1, and low thermal conductivity of 1.4-1.7 W center dot m- 1 center dot K- 1.
MATERIALS SCIENCE IN SEMICONDUCTOR PROCESSING
(2023)
Article
Energy & Fuels
Masashi Matsumi, Kazuhiro Gotoh, Markus Wilde, Yasuyoshi Kurokawa, Katsuyuki Fukutani, Noritaka Usami
Summary: A two-step hydrogen plasma treatment was used to improve the passivation performance of Si nanocrystals/silicon oxide compound passivating contacts. This treatment enhanced the hydrogenation of the Si nanocrystals/silicon oxide compound layer, leading to an improved implied open-circuit voltage. However, it also resulted in an increase in contact resistivity.
SOLAR ENERGY MATERIALS AND SOLAR CELLS
(2023)
Article
Chemistry, Multidisciplinary
Yuqing Li, Hitoshi Sai, Calum Mcdonald, Zhihao Xu, Yasuyoshi Kurokawa, Noritaka Usami, Takuya Matsui
Summary: This study investigates the influence of nanoscale Si pyramid textures on the performance of perovskite/Si tandem solar cells. It is found that excessive texture size leads to non-uniform top-cell formation and reduced performance. However, reducing the texture size within a certain range can suppress reflection and enhance the open-circuit voltage and current of the cell.
ADVANCED MATERIALS INTERFACES
(2023)
Article
Chemistry, Physical
Kosuke O. Hara, Ryota Takagaki, Keisuke Arimoto, Noritaka Usami
Summary: In this study, the microstructure and its effects on the electrical and optoelectronic properties of BaSi2 films grown by close-spaced evaporation were investigated. It was found that using Si(100) substrates, increasing film thickness and growth temperature can decrease the density of epitaxial domain boundaries, improve carrier lifetime, and enhance the performance of BaSi2 films for photovoltaic applications.
JOURNAL OF ALLOYS AND COMPOUNDS
(2023)
Article
Nanoscience & Nanotechnology
Yuto Kimata, Kazuhiro Gotoh, Satoru Miyamoto, Shinya Kato, Yasuyoshi Kurokawa, Noritaka Usami
Summary: Vehicle-integrated photovoltaics (VIPV) is a promising technology for achieving a decarbonized society in the future. The solar cells used in VIPV require low cost, high efficiency, and the ability to be applied to curved surfaces. One way to meet these requirements is by reducing the thickness of the silicon substrate, although it may result in lower near-infrared light absorption and efficiency. To address this issue, a nanoimprinting method was employed in this study to fabricate submicron-sized light trapping structures (LTSs) on solar cells over a large area. By controlling the parameters such as silica coverage, diameter of silica particles, and etching time, the density, height, and size of LTSs can be controlled, leading to improved light absorption and potential short-circuit current gain.
Article
Chemistry, Multidisciplinary
Kenta Yamakoshi, Yutaka Ohno, Kentaro Kutsukake, Takuto Kojima, Tatsuya Yokoi, Hideto Yoshida, Hiroyuki Tanaka, Xin Liu, Hiroaki Kudo, Noritaka Usami
Summary: A comprehensive analysis of optical and photoluminescence images from multicrystalline silicon wafers is conducted using machine learning models, resulting in the establishment of a realistic 3D model that includes the generation point of dislocation clusters. The study reveals the mechanism of dislocation generation and its importance in materials science.
ADVANCED MATERIALS
(2023)
