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34 results on '"Teii, Kungen"'

4. Special Issue on the APSPT 2021

Author

Chen, Jian-Zhang, primary, Wang, Meng-Jiy, additional, Lin, Kun-Mo, additional, Cheng, Yun-Chien, additional, Teii, Kungen, additional, and Ito, Hiroaki, additional

Published
2023
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10. Effect of Precursor Gas on Growth Temperature and Electrical Conduction of Carbon Nanowalls in Microwave Plasma-Enhanced Chemical Vapor Deposition

Author

Huang, Lei, Ikematsu, Hiroto, Kato, Yoshimine, and Teii, Kungen

Abstract

Moderate-pressure microwave plasmas are used to prepare nitrogen-incorporated carbon nanowalls (CNWs) by chemical vapor deposition using acetylene and methane as precursor gases. The growth temperature range for acetylene is shown to be totally lower than that (>1000 °C) for methane, which is attributed to the difference in degree of hydrogenation of radical species in the two plasmas. The structural order and cluster size of sp2 carbon phase in CNWs characterized by the Raman spectroscopy increase initially and, then, decrease with temperature in each temperature range, showing the same trend as the inverse of the sheet resistance of CNWs. The results indicate that the carrier transport in CNWs depends exclusively on the microstructure of sp2 carbon phase, despite a large difference in the growth temperature range depending on the precursor gas.

Published
2023
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18. Thermal stability of boron nitride/silicon p-n heterojunction diodes.

Author

Teii, Kungen, Mizusako, Yusei, Hori, Takuro, and Matsumoto, Seiichiro

Subjects
*BORON nitride, *SILICON research, *THERMAL stability, *DIODES, *CHEMICAL vapor deposition
Abstract

Heterojunctions of p-type cubic boron nitride (cBN) and n-type silicon with sp2-bonded BN (sp2BN) interlayers are fabricated under low-energy ion impact by plasma-enhanced chemical vapor deposition, and their rectification properties are studied at temperatures up to 573 K. The rectification ratio is increased up to the order of 105 at room temperature by optimizing the thickness of the sp2BN interlayer and the cBN fraction for suppressing the reverse leakage current. A highly rectifying p-type cBN/thick sp2BN/n-type silicon junction diode shows irreversible rectification properties mainly characterized by a marked decrease in reverse current by an order of magnitude in an initial temperature ramp/down cycle. This irreversible behavior is much more reduced by conducting the cycle twice or more. The temperature-dependent properties confirm an overall increase in effective barrier heights for carrier injection and conduction by biasing at high temperatures, which consequently increases the thermal stability of the diode performance. [ABSTRACT FROM AUTHOR]

Published
2015
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21. Biocompatible Cubic Boron Nitride: A Noncytotoxic Ultrahard Material.

Author

Yang, Jason H. C., Teii, Kungen, Chang, Chung‐Chueh, Matsumoto, Seiichiro, and Rafailovich, Miriam

Subjects
*BORON nitride, *PLASMA-enhanced chemical vapor deposition, *BIOMATERIALS, *MINES & mineral resources, *NITROGEN plasmas, *DIAMOND films
Abstract

Cubic boron nitride (c‐BN) has an ultrahardness and a large bandgap energy like diamond. In the last 30 years, most of the attention has been directed towards the mechanical and electronic applications of c‐BN, while its biological potential has been overlooked. The authors report in vitro biocompatibility of high‐quality c‐BN films prepared by plasma‐enhanced chemical vapor deposition using the chemistry of fluorine. c‐BN films become superhydrophilic when chemical‐treated in hydrogen and nitrogen plasmas with or without the impact of low‐energy ions due to a marked increase in polar part of the surface free energy by removal of the fluorine atoms terminating c‐BN surfaces. Satisfactory proliferation and differentiation of osteoblastic cells comparable with a control sample and a superhydrophilic nanocrystalline diamond film, and the formation of mineral deposits by biomineralization are confirmed on the superhydrophilic c‐BN films with negative values of zeta potential. The results demonstrate a high potential of c‐BN as a noncytotoxic ultrahard coating material for biological and biomedical applications. [ABSTRACT FROM AUTHOR]

Published
2021
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34. Formation of nanocrystalline diamond cones by reactive ion etching in microwave plasma for enhancing field emission

Author

Ota, Koki, Kato, Yoshimine, and Teii, Kungen

Abstract

Cone-like nanostructures are formed on nitrogen-incorporated nanocrystalline diamond films by reactive ion etching (RIE) in a moderate-pressure microwave plasma. A thin Au layer is deposited on the film and followed by heating for transformation of an Au layer into Au nanoparticles as the mask for RIE. The diameter and spacing of Au nanoparticles depend upon the heating temperature and the thickness of Au. The smooth film surface is transformed into a number of cone-like protrusions with diameters, heights, and spacings of tens to a few hundreds of nm by RIE in a hydrogen/argon plasma and removal of Au residue in aqua regia. The formation of sharp nanostructures enhances field emission characteristics, so that the current density at high fields is increased largely up to the order of 10[?]3 A cm[?]2 and the turn-on field is reduced down to around 1.8 V um[?]1, comparable to other carbon nanostructures, due to enhancement of local fields.

Published
2019

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