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8 results on '"Komatsu, Hibiki"'

6. Influence of Cr2O3 Concentration on the Green Color of Flux Synthesized Emeralds Using the CIE1976 Color System.

Author

Kozaki, Daisuke, Yanagisawa, Kazumichi, Oishi, Shuji, Nishiwaki, Yoshinori, Komatsu, Hibiki, Kobiro, Kazuya, Ito, Akitaka, Taniguchi, Ayano, and Matsuzaki, Takuya

Abstract

The color of emeralds is predominantly influenced by the concentration of Cr3+. However, the evaluation of the trend of green color depth of emeralds, based on the practical single crystal synthesis with several instrumental analysis is not investigated in previous researches. Specifically, if the Cr2O3 content is controlled to be in the range of 0.2–0.4 wt%, then emeralds can be synthesized with the most esthetically pleasing color. Therefore, the effect of Cr2O3 concentration within the aforementioned range on the color of emeralds is studied using powder X‐ray diffractometry, digital microscopy, electron probe microanalysis, and micro‐spectrophotometry to understand how to achieve the most esthetically pleasing color. As a result, detailed behaviors relating to the absorbances, L*, a*, and b* values, and the relationship between the emerald crystal color changes and increases in Cr2O3 concentration are elucidated. Notably, the absorbance, L* and a* values change significantly when the Cr2O3 concentration is low (0.00–0.236 wt%). However, the changes in these values are moderate when the Cr2O3 concentration is higher (0.236–0.504 wt%). [ABSTRACT FROM AUTHOR]

Published
2023
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8. Hydrogen-included plasma-assisted reactive sputtering for conductivity control of ultra-wide bandgap amorphous gallium oxide

Author

Takenaka, Kosuke, Komatsu, Hibiki, Sagano, Taichi, Ide, Keisuke, Toko, Susumu, Katase, Takayoshi, Kamiya, Toshio, and Setsuhara, Yuichi

Abstract

Conductivity control of a-Ga2Oxfilms by cation/anion off-stoichiometry such as oxygen vacancy formation and hydrogen doping have been achieved by hydrogen-included plasma-assisted reactive sputter deposition system and physical and electrical properties of a-Ga2Oxfilms formed by this system have been investigated. The change in resistivity of a-Ga2Oxthin films deposited by the hydrogen-included plasma-assisted reactive sputtering was then investigated by changing the H2flow rate ratio H2/(Ar + H2). The a-Ga2Oxthin films with semiconducting properties with a resistivity as low as 102 Ωcm was demonstrated using the plasma-assisted reactive sputtering system with addition to H2. Along with the low resistivity, the a-GaOxthin films with high film density and band gap energy of 5.2 g cm−3and 4.8 eV were realized. The electrical resistivity of the a-Ga2Oxthin films can be controlled from 102 Ωcm to 105 Ωcm by appropriately controlling the amount of hydrogen introduced from the plasma. The results indicate that the hydrogen acts as a shallow donor, which increases the carrier concentration, can be efficiently introduced by using the plasma-assisted reactive sputtering system with addition to H2.

Published
2024
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