Weijie Du, Mitsushi Suzuno, M. Ajmal Khan, Katsuaki Toh, Masakazu Baba, Kotaro Nakamura, Kaoru Toko, Noritaka Usami, Takashi Suemasu,
... Toh, Masakazu Baba, Kotaro Nakamura, Kaoru Toko, Noritaka Usami, Takashi Suemasu; Improved photoresponsivity of semiconducting BaSi2 epitaxial films ...
Tópico(s): Semiconductor materials and devices
2012 - American Institute of Physics | Applied Physics Letters
... Chuchird, Shingo Hiramatsu, Ichiro Sugimoto, Makoto Fujie, Shoji Usami, Takashi Yamada Digestion of Chlorella Cells by Chlorovirus-encoded ...
Tópico(s): Marine and coastal plant biology
1936 - University of Chicago Press | The American Naturalist
Masakazu Baba, Kentaro Watanabe, Kosuke O. Hara, Kaoru Toko, Takashi Sekiguchi, Noritaka Usami, Takashi Suemasu,
We have grown a 400-nm-thick undoped n-BaSi2 epitaxial film on an n-Si(001) substrate by molecular beam epitaxy, and evaluated the diffusion length of minority carriers (holes) by an electron-beam-induced-current (EBIC) technique in the edge-scan configuration. The EBIC line-scan profile showed an exponential dependence on the distance from the tungsten probe. The diffusion length of minority carriers in the n-BaSi2 film was found to be approximately 1.5 µm. This value is much smaller than that in ...
Tópico(s): Semiconductor materials and devices
2014 - Institute of Physics | Japanese Journal of Applied Physics
Weijie Du, Masakazu Baba, Kaoru Toko, Kosuke O. Hara, Kentaro Watanabe, Takashi Sekiguchi, Noritaka Usami, Takashi Suemasu,
Current status and future prospects towards BaSi2 pn junction solar cells are presented. As a preliminary step toward the formation of BaSi2 homojunction diodes, diodes with a Cr/n-BaSi2 Schottky junction and an n-BaSi2/p-Si hetero-junction have been fabricated to investigate the electrical properties of the n-BaSi2. Clear rectifying properties were observed in the current density versus voltage characteristics in both diodes. From the capacitance-voltage measurements, the build-in potential, VD, ...
Tópico(s): Integrated Circuits and Semiconductor Failure Analysis
2014 - American Institute of Physics | Journal of Applied Physics
Masakazu Baba, Katsuaki Toh, Kaoru Toko, Noriyuki Saito, Noriko Yoshizawa, Karolin Jiptner, Takashi Sekiguchi, Kosuke O. Hara, Noritaka Usami, Takashi Suemasu,
a-Axis-oriented undoped n-BaSi2 epitaxial films were grown on Si(111) substrates by molecular beam epitaxy, and the crystalline quality and grain boundaries were investigated by means of reflection high-energy electron diffraction, X-ray diffraction, and transmission electron microscopy (TEM). The grain size of the BaSi2 films was estimated to be approximately 0.1–0.3 μm, and straight grain boundaries (GBs) were observed in the plan-view TEM images. Dark-field TEM images under a two-beam diffraction ...
Tópico(s): Integrated Circuits and Semiconductor Failure Analysis
2012 - Elsevier BV | Journal of Crystal Growth
Taketoshi Suzuki, Riku Usami, Takashi Maekawa,
In this paper, we introduce an algorithm for generating collision-free two-lane paths for unmanned vehicles used at mining sites by using quartic (degree 4) B-spline curves. Given the boundary geometry of the haul road area and the positions and orientations of the two-dimensional vehicle at the start and goal points, the algorithm automatically generates a collision-free two-lane path that satisfies the minimum turning radius constraint. Moreover, the resulting path shares the same third derivative ...
Tópico(s): Human Motion and Animation
2018 - Institute of Electrical and Electronics Engineers | IEEE Transactions on Intelligent Vehicles
Daichi Tsukahara, Suguru Yachi, Hiroki Takeuchi, Ryota Takabe, Weijie Du, Masakazu Baba, Yunpeng Li, Kaoru Toko, Noritaka Usami, Takashi Suemasu,
p-BaSi2/n-Si heterojunction solar cells consisting of a 20 nm thick B-doped p-BaSi2 epitaxial layer (p = 2.2 × 1018 cm−3) on n-Si(111) (ρ = 1–4 Ω cm) were formed by molecular beam epitaxy. The separation of photogenerated minority carriers is promoted at the heterointerface in this structure. Under AM1.5 illumination, the conversion efficiency η reached 9.0%, which is the highest ever reported for solar cells with semiconducting silicides. An open-circuit voltage of 0.46 V, a short-circuit current density ...
Tópico(s): Chalcogenide Semiconductor Thin Films
2016 - American Institute of Physics | Applied Physics Letters
Wenjie Du, R. Takabe, Masako Baba, Hiroki Takeuchi, Kosuke O. Hara, Kaoru Toko, Noritaka Usami, Takashi Suemasu,
Heterojunction solar cells that consist of 15 nm thick molybdenum trioxide (MoOx, x < 3) as a hole transport layer and 600 nm thick unpassivated or passivated n-BaSi2 layers were demonstrated. Rectifying current-voltage characteristics were observed when the surface of BaSi2 was exposed to air. When the exposure time was decreased to 1 min, an open circuit voltage of 200 mV and a short circuit current density of 0.5 mA/cm2 were obtained under AM1.5 illumination. The photocurrent density under a ...
Tópico(s): Semiconductor materials and devices
2015 - American Institute of Physics | Applied Physics Letters
Kaoru Toko, Ryohei Numata, Oya N, Naoki Fukata, Noritaka Usami, Takashi Suemasu,
The Al-induced crystallization (AIC) yields a large-grained (111)-oriented Ge thin film on an insulator at temperatures as low as 180 °C. We accelerated the AIC of an amorphous Ge layer (50-nm thickness) by initially doping Ge in Al and by facilitating Ge diffusion into Al. The electron backscatter diffraction measurement demonstrated the simultaneous achievement of large grains over 10 μm and a high (111) orientation fraction of 90% in the polycrystalline Ge layer formed at 180 °C. This result opens ...
Tópico(s): Silicon Nanostructures and Photoluminescence
2014 - American Institute of Physics | Applied Physics Letters
Kaoru Toko, Ryohei Numata, Noriyuki Saitoh, Noriko Yoshizawa, Noritaka Usami, Takashi Suemasu,
By controlling the Si thickness and the annealing temperature used for Al-induced crystallization, we controlled the fraction of (100) and (111) orientations of polycrystalline Si (poly-Si) grains grown on glass. Changing the proportions of crystal orientation strongly influenced the average grain size of the poly-Si layer. By growing a 99% (111)-oriented poly-Si layer, formed with a 50-nm-thick Si layer at 375 °C, we produced a Si layer with grains nearly 40 μm in size. We discuss the growth mechanism ...
Tópico(s): Silicon and Solar Cell Technologies
2014 - American Institute of Physics | Journal of Applied Physics
Ryota Takabe, Kosuke O. Hara, Masakazu Baba, Weijie Du, Naoya Shimada, Kaoru Toko, Noritaka Usami, Takashi Suemasu,
We have fabricated approximately 0.5-μm-thick undoped n-BaSi2 epitaxial films with various average grain areas ranging from 2.6 to 23.3 μm2 on Si(111) by molecular beam epitaxy, and investigated their minority-carrier lifetime properties by the microwave-detected photoconductivity decay method at room temperature. The measured excess-carrier decay curves were divided into three parts in terms of decay rate. We characterized the BaSi2 films using the decay time of the second decay mode, τSRH, caused ...
Tópico(s): Chalcogenide Semiconductor Thin Films
2014 - American Institute of Physics | Journal of Applied Physics
R. Takabe, Kotaro Nakamura, Masakazu Baba, Weiji Du, M. Ajmal Khan, Kaoru Toko, Masato Sasase, Kosuke O. Hara, Noritaka Usami, Takashi Suemasu,
We attempted to fabricate a -axis-oriented BaSi 2 epitaxial films up to 2180 nm in thickness. First, we investigated the influence of growth temperature and growth rate on the crystalline quality of approximately 400-nm-thick BaSi 2 layers, and then optimized the above two growth conditions based on X-ray diffraction measurements. We next grew BaSi 2 films with various layer thicknesses at 580 °C in the range between 100 and 2180 nm, and characterized their properties. The a -axis-oriented BaSi 2 thick ...
Tópico(s): Semiconductor materials and devices
2014 - Institute of Physics | Japanese Journal of Applied Physics
Kaoru Toko, Kimitaka Nakazawa, Noriyuki Saitoh, Noriko Yoshizawa, Noritaka Usami, Takashi Suemasu,
The crystal orientation of a polycrystalline Ge thin film is controlled by selecting the underlayer material during Al-induced low-temperature (325 °C) crystallization. A TiN underlayer yields highly (111)-oriented Ge with large grains (nearly 100 μm), which is useful as a buffer layer for III–V compound semiconductors and other advanced materials.
Tópico(s): Semiconductor materials and devices
2014 - Royal Society of Chemistry | CrystEngComm
M. Ajmal Khan, Kotaro Nakamura, Wenjie Du, Kaoru Toko, Noritaka Usami, Takashi Suemasu,
Precipitation free boron (B)-doped as-grown p+-BaSi2 layer is essential for the BaSi2 p-n junction solar cells. In this article, B-doped p-BaSi2 layers were grown by molecular beam epitaxy on Si(111) substrates, and the influence of substrate growth temperature (TS) and B temperature (TB) in the Knudsen cell crucible were investigated on the formation of B precipitates and the activation efficiency. The hole concentration, p, reached 1.0 × 1019 cm−3 at room temperature for TS = 600 and TB = 1550 °C. However, ...
Tópico(s): Chalcogenide Semiconductor Thin Films
2014 - American Institute of Physics | Applied Physics Letters
M. Ajmal Khan, Kosuke O. Hara, Kotaro Nakamura, Weijie Du, Masakazu Baba, Katsuaki Toh, Mitsushi Suzuno, Kaoru Toko, Noritaka Usami, Takashi Suemasu,
We have successfully grown a-axis-oriented p-type BaSi 2 films on Si(111) by in situ boron (B) doping using molecular beam epitaxy (MBE).The hole concentration in B-doped BaSi 2 was controlled in the range between 10 17 and 10 19 cm -3 at room temperature by changing the temperature of the B Knudsen cell crucible.The acceptor level was estimated to be approximately 23 meV.
Tópico(s): Silicon and Solar Cell Technologies
2013 - Elsevier BV | Journal of Crystal Growth
Ryohei Numata, Kaoru Toko, Koki Nakazawa, Noritaka Usami, Takashi Suemasu,
Al-induced crystallization (AIC) enables low-temperature crystallization of amorphous Ge thin films on insulators. We investigated growth promotion of Ge thin films using Ge membranes (1–10 nm thickness) that are initially inserted below the Al layer. These Ge insertion layers enhanced supersaturation of Al with Ge, which results in low-temperature AIC (275 °C). However, thick (≥ 3 nm) insertion layers result in small grains because of the high nucleation frequency. A 1-nm-thick insertion layer accomplished ...
Tópico(s): Semiconductor materials and devices
2013 - Elsevier BV | Thin Solid Films
Kimitaka Nakazawa, Kaoru Toko, Noriyuki Saitoh, Noriko Yoshizawa, Noritaka Usami, Takashi Suemasu,
Low-temperature (350°C) crystallization of amorphous Ge films on SiO2 was investigated using Al-induced layer exchange (ALILE) process. Thicknesses of Ge and catalytic Al layers were varied in the range of 30–300 nm, which strongly influenced the ALILE growth morphology. Based on the study, the Ge thickness was adjusted to 40 nm while the Al thickness was adjusted 50 nm. This sample satisfied both of the surface coverage of polycrystalline-Ge and the annihilation of randomly oriented Ge regions. Moreover, ...
Tópico(s): Nanowire Synthesis and Applications
2013 - Institute of Physics | ECS Journal of Solid State Science and Technology
Masakazu Baba, Sadahiro Tsurekawa, Kentaro Watanabe, Weijie Du, Kaoru Toko, Kosuke O. Hara, Noritaka Usami, Takashi Sekiguchi, Takashi Suemasu,
Potential variations around the grain boundaries (GBs) on the surface in undoped n-BaSi2 epitaxial films on Si(111) and Si(001) were analyzed using Kelvin prove force microcopy. The potentials were higher at GBs than those in the BaSi2 grains on Si(111). The average barrier height was approximately 30 meV at the GBs, indicating that the enhanced potentials repulse photogenerated holes so that the charge carrier recombination can be effectively reduced. In contrast, the potentials were smaller at ...
Tópico(s): Integrated Circuits and Semiconductor Failure Analysis
2013 - American Institute of Physics | Applied Physics Letters
Kaoru Toko, Koki Nakazawa, Noriyuki Saitoh, Noriko Yoshizawa, Noritaka Usami, Takashi Suemasu,
A large-grained (111)-oriented Ge thin film is achieved on a SiO2 glass substrate using an Al-induced crystallization (AIC) technique. Low-temperature (350 °C) AIC of an amorphous Ge thin film (50 nm thickness) resulted in a self-organized double-layered structure of polycrystalline Ge layers. The top Ge layer consisted of randomly oriented small grains (1 μm diameter) with a high defect density; in contrast, the bottom Ge layer was of high quality. Based on the growth model, we annihilated the top Ge ...
Tópico(s): Semiconductor materials and interfaces
2013 - American Chemical Society | Crystal Growth & Design
Ryohei Numata, Kaoru Toko, Noriyuki Saitoh, Noriko Yoshizawa, Noritaka Usami, Takashi Suemasu,
The thickness-modulated Al-induced crystallization technique enables us to control the orientation of polycrystalline Si films on insulators. The amorphous Si film on a SiO2 substrate was crystallized at a low temperature (425 °C) through the layer exchange between Si and catalytic Al layers. Electron backscattering diffraction (EBSD) measurements revealed that the crystal orientation of the grown Si layer varied significantly depending on the Al/Si thickness: The [111]-orientation fraction reached ...
Tópico(s): Silicon and Solar Cell Technologies
2013 - American Chemical Society | Crystal Growth & Design
M. Ajmal Khan, Kosuke O. Hara, Weijie Du, Masako Baba, Kotaro Nakamura, Mitsushi Suzuno, Kaoru Toko, Noritaka Usami, Takashi Suemasu,
B-doped p-BaSi2 layer growth by molecular beam epitaxy and the influence of rapid thermal annealing (RTA) on hole concentrations were presented. The hole concentration was controlled in the range between 1017 and 1020 cm−3 at room temperature by changing the temperature of the B Knudsen cell crucible. The acceptor level of the B atoms was estimated to be approximately 23 meV. High hole concentrations exceeding 1 × 1020 cm−3 were achieved via dopant activation using RTA at 800 °C in Ar. The activation ...
Tópico(s): Semiconductor materials and devices
2013 - American Institute of Physics | Applied Physics Letters
Atsushi Okada, Kaoru Toko, Kosuke O. Hara, Noritaka Usami, Takashi Suemasu,
We have fabricated poly-Si thin films on fused silica substrates by the Al-induced crystallization (AIC) method with SiO2 insertion layers of various thicknesses (0–20 nm). The growth morphologies of poly-Si layers were dramatically changed by the SiO2 thickness, i.e., thin layers (2 nm) provided high growth rates and (100) orientations, and thick layers (10 nm) provided low growth rates and (111) orientations. These results showed that the crystal orientation of AIC-Si significantly depends on the diffusion ...
Tópico(s): Semiconductor materials and interfaces
2012 - Elsevier BV | Journal of Crystal Growth
Naoto Isono, Hiroka Hayakawa, Atsuko Usami, Takashi Mishima, Makoto Hisamatsu,
The ability of 13 strains of multi-stress-tolerant Issatchenkia orientalis yeast to produce ethanol was examined under different stress conditions, including conditions of elevated H2SO4 and Na2SO4 concentrations and increased heat. The MF-121 strain produced a significant amount of ethanol after the incubation in acidic media containing high concentrations of salt, e.g., 50 g/l Na2SO4 at pH 2.0, or at high temperatures, e.g., 43°C, when compared with other strains.
Tópico(s): Fungal and yeast genetics research
2011 - Elsevier BV | Journal of Bioscience and Bioengineering
Hiroaki Minegishi, Masahiro Kamekura, Tomomi Kitajima‐Ihara, Kaoru Nakasone, Akinobu Echigo, Yasuhiro Shimane, Ron Usami, Takashi Itoh, Kunio Ihara,
In many prokaryotic species, 16S rRNA genes are present in multiple copies, and their sequences in general do not differ significantly owing to concerted evolution. At the time of writing, the genus Haloarcula of the family Halobacteriaceae comprises nine species with validly published names, all of which possess two to four highly heterogeneous 16S rRNA genes. Existence of multiple heterogeneous 16S rRNA genes makes it difficult to reconstruct a biological phylogenetic tree using their sequence ...
Tópico(s): Protist diversity and phylogeny
2011 - Microbiology Society | INTERNATIONAL JOURNAL OF SYSTEMATIC AND EVOLUTIONARY MICROBIOLOGY
Dai Tsukada, Yuta Matsumoto, Ryo Sasaki, Michitoshi Takeishi, Takanobu Saito, Noritaka Usami, Takashi Suemasu,
We have prepared (1 1 1)-oriented Si layers on SiO2 (fused silica) substrates from amorphous-Si(a-Si)/Al or Al/a-Si stacked layers using an aluminum-induced crystallization (AIC) method. The X-ray diffraction (XRD) intensity from the (1 1 1) planes of Si was found to depend significantly on growth conditions such as the thicknesses of Si and Al, deposition order (a-Si/Al or Al/a-Si on SiO2), deposition technique (sputtering or vacuum evaporation) and exposure time of the Al layer to air before the deposition ...
Tópico(s): Silicon and Solar Cell Technologies
2009 - Elsevier BV | Journal of Crystal Growth
Dai Tsukada, Yuta Matsumoto, Ryo Sasaki, Michitoshi Takeishi, Takanobu Saito, Noritaka Usami, Takashi Suemasu,
Polycrystalline BaSi2 layers with 300 nm thickness were grown by molecular beam epitaxy on (111)-oriented 100-nm-thick polycrystalline Si layers fabricated by an aluminum-induced crystallization method on SiO2. Photocurrents were clearly observed for photons with energies greater than 1.25 eV when bias voltage was applied between the 1.5-mm-spacing striped Al electrodes formed on the surface. The photoresponsivity increased sharply with increasing photon energy, attaining a maximum at approximately ...
Tópico(s): Semiconductor materials and devices
2009 - Institute of Physics | Applied Physics Express
Tetsuya Oishi, Aritoshi Iida, Shigeru Otsubo, Yoichiro Kamatani, Masayuki Usami, Takashi Takei, Keiko Uchida, Ken Tsuchiya, Susumu Saito, Yozo Ohnisi, Katsushi Tokunaga, Kosaku Nitta, Yasushi Kawaguchi, Naoyuki Kamatani, Yuta Kochi, Kenichi Shimane, Kazuhiko Yamamoto, Yusuke Nakamura, Wako Yumura, Koichi Matsuda,
Systemic lupus erythematosus (SLE) is one of the common autoimmune diseases with complex genetic components. To identify a gene(s) susceptible to SLE, we performed a case-control association study using genome-wide gene-based single nucleotide polymorphisms (SNPs) in Japanese population. Here we report that an SNP (rs3748079) located in a promoter region of the inositol 1,4,5-triphosphate receptor type 3 (ITPR3) gene on chromosome 6p21 was significantly associated with SLE in two independent Japanese ...
Tópico(s): Diabetes and associated disorders
2008 - Springer Nature | Journal of Human Genetics
Takeru Kawasaki, Mio Shimizu, Hideki Satsuma, Akiko Fujiwara, Makoto Fujie, Shoji Usami, Takashi Yamada,
PhiRSB1 is a wide-host-range, T7-like bacteriophage that infects and efficiently lyses the phytopathogenic bacterium Ralstonia solanacearum. The phiRSB1 genome comprises 43,079 bp of double-stranded DNA (61.7% G+C) with 325-bp terminal repeats and contains 47 open reading frames. Strong activity of tandem early promoters and wide specificity of phage promoters of phiRSB1 were demonstrated.
Tópico(s): Genomics and Phylogenetic Studies
2008 - American Society for Microbiology | Journal of Bacteriology
Takeru Kawasaki, Shoko Nagata, Akiko Fujiwara, Hideki Satsuma, Makoto Fujie, Shoji Usami, Takashi Yamada,
The genomic DNA sequences were determined for two filamentous integrative bacteriophages, phiRSS1 and phiRSM1, of the phytopathogen Ralstonia solanacearum. The 6,662-base sequence of phiRSS1 contained 11 open reading frames (ORFs). In the databases, this sequence showed high homology (95% identity) to the circular double-stranded DNA plasmid pJTPS1 (6,633 bp) isolated from a spontaneously occurring avirulent mutant of R. solanacearum. Two major differences between the two sequences were observed within ...
Tópico(s): Genomics and Phylogenetic Studies
2007 - American Society for Microbiology | Journal of Bacteriology
Takeru Kawasaki, Hideki Satsuma, Makoto Fujie, Shoji Usami, Takashi Yamada,
Tópico(s): Plant-Microbe Interactions and Immunity
2007 - Elsevier BV | Journal of Bioscience and Bioengineering