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250 results on '"Kurashima, Yuichi"'

11. Ultra-High Vacuum Cells Realized by Miniature Ion Pump Using High-Efficiency Plasma Source.

Author

Kurashima, Yuichi, Maeda, Atsuhiko, Oshima, Naoto, Motomura, Taisei, Matsumae, Takashi, Watanabe, Mitsuhiro, and Takagi, Hideki

Subjects
*ULTRAHIGH vacuum, *PLASMA sources, *ATOMIC clocks, *QUANTUM computers, *COMPUTER performance, *VACUUM chambers
Abstract

In recent years, there has been significant interest in quantum technology, characterized by the emergence of quantum computers boasting immense processing power, ultra-sensitive quantum sensors, and ultra-precise atomic clocks. Miniaturization of quantum devices using cold atoms necessitates the employment of an ultra-high vacuum miniature cell with a pressure of approximately 10−6 Pa or even lower. In this study, we developed an ultra-high vacuum cell realized by a miniature ion pump using a high-efficiency plasma source. Initially, an unsealed miniature ion pump was introduced into a vacuum chamber, after which the ion pump's discharge current, depending on vacuum pressures, was evaluated. Subsequently, a miniature vacuum cell was fabricated by hermetically sealing the miniature vacuum pump. The cell was successfully evacuated by a miniature ion pump down to an ultra-high vacuum region, which was derived by the measured discharge current. Our findings demonstrate the feasibility of achieving an ultra-high vacuum cell necessary for the operation of miniature quantum devices. [ABSTRACT FROM AUTHOR]

Published
2024
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23. Low-temperature direct bonding of SiC and Ga2O3 substrates under atmospheric conditions.

Author

Matsumae, Takashi, Kurashima, Yuichi, Takagi, Hideki, Umezawa, Hitoshi, and Higurashi, Eiji

Subjects
*WEATHER, *AERODYNAMIC heating, *SURFACE cleaning, *DEHYDRATION reactions
Abstract

In this study, SiC and Ga2O3 substrates were bonded under atmospheric conditions using an extremely thin amorphous layer (∼7 Å). Conventional wafer-bonding techniques employ an oxidizing treatment for surface functionalization, resulting in the formation of an oxide layer at the bonding interface. This study demonstrates the bonding of a hydrofluoric-acid-treated SiC surface with a plasma-activated Ga2O3 substrate, where the –OH groups on the SiC and Ga2O3 surfaces form direct bonding via a dehydration reaction at 250 °C. The interfacial analysis indicates that bonding using the reduction treatment instead of oxidization reduces the thickness of the intermediate layer at the SiC/Ga2O3 interface, which is a thermal and electrical barrier. In addition, it is remarkable that the SiC and Ga2O3 substrates are directly bonded by generally used surface cleaning processes, contacting the surfaces under atmospheric conditions, and annealing at 250 °C. We believe that the bonding process using the reduction process can contribute to future heterogeneous devices based on integrated dissimilar substrates. [ABSTRACT FROM AUTHOR]

Published
2021
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26. 12-inch X-ray optics based on MEMS process

Author

Ishikawa, Kumi, Ezoe, Yuichiro, Numazawa, Masaki, Ogawa, Tomohiro, Sato, Mayu, Nakamura, Kasumi, Ohashi, Takaya, Mitsuda, Kazuhisa, Maeda, Ryutaro, Hiroshima, Hiroshi, Kurashima, Yuichi, and Noda, Daiji

Published
2017
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50. Hydrophilic direct bonding of GaN and Si substrates by wet treatments using H2SO4/H2O2 mixture and NH3/H2O2 mixture.

Author

Fukumoto, Shoya, Matsumae, Takashi, Kurashima, Yuichi, Takagi, Hideki, Hayase, Masanori, and Higurashi, Eiji

Abstract

GaN substrates were directly bonded with Si substrates by wet treatments using H2SO4/H2O2 and NH3/H2O2 mixtures. Under the optimized condition, the tensile strength reached 7.36 MPa, and a part of the Si substrate was fractured within the bulk instead of the bonding interface. There is an amorphous intermediate layer with a thickness of 1.7 nm, which mainly consists of Si oxides, at the bonding interface. It is remarkable that wafer-scale GaN/Si integration was successfully achieved by using common cleaning methods. It is believed that the proposed direct bonding technique would contribute to future heterogeneous integration because the GaN and Si substrates can be bonded through the atomically thin intermediate layer without vacuum processes. [ABSTRACT FROM AUTHOR]

Published
2022
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