SiO/AlON stacked gate dielectrics for AlGaN/GaN MOS heterojunction field-effect transistors

Watanabe, Kenta*; Terashima, Daiki*; Nozaki, Mikito*; Yamada, Takahiro*; Nakazawa, Satoshi*; Ishida, Masahiro*; Anda, Yoshiharu*; Ueda, Tetsuzo*; Yoshigoe, Akitaka; Hosoi, Takuji*; et al.

Japanese Journal of Applied Physics, 57(6S3), p.06KA03_1 - 06KA03_6, 2018/06

https://doi.org/10.7567/JJAP.57.06KA03

The advantage of SiO/AlON stacked gate dielectrics over SiO, AlON and AlO single dielectric layers was demonstrated. Our systematic research revealed that the optimized stacked structure with 3.3-nm-thick AlON interlayer is beneficial in terms of superior interface quality, reduced gate leakage current and C-V hysteresis for next-generation high frequency and high power AlGaN/GaN MOS-HFETs.

X-ray absorption spectroscopy in the heavy Fermion compound -YbAlB at high magnetic fields

Terashima, Taku*; Matsuda, Yasuhiro*; Kuga, Kentaro*; Suzuki, Shintaro*; Matsumoto, Yosuke*; Nakatsuji, Satoru*; Kondo, Akihiro*; Kindo, Koichi*; Kawamura, Naomi*; Mizumaki, Masaichiro*; et al.

Journal of the Physical Society of Japan, 84(11), p.114715_1 - 114715_4, 2015/11

https://doi.org/10.7566/JPSJ.84.114715

Synchrotron X-ray spectroscopy study on the valence state and magnetization in -YbAlFeB () at low temperatures and high magnetic fields

Terashima, Taku*; Matsuda, Yasuhiro*; Kuga, Kentaro*; Suzuki, Shintaro*; Matsumoto, Yosuke*; Nakatsuji, Satoru*; Kondo, Akihiro*; Kindo, Koichi*; Kawamura, Naomi*; Mizumaki, Masaichiro*; et al.

Journal of Physics; Conference Series, 592(1), p.012020_1 - 012020_6, 2015/03

https://doi.org/10.1088/1742-6596/592/1/012020

Valence fluctuation phenomena in rare-earth intermetallic compounds have attracted attention because the quantum criticality of the valence transition has been proposed theoretically. Recently, it was found that -YbAlB shows quantum criticality without tuning and has a strong mixed-valence state. In this study, we measured the magnetization curve and X-ray magnetoabsorption in -YbAlFeB (), which is a locally isostructural polymorph of -YbAlB. The magnetization and X-ray experiments were performed in fields up to 55 and 40 T, respectively. A small increase in the Yb valence was observed at fields where the magnetization curve exhibited a change in slope.

Modification of the generic NICA-Donnan model parameter for the modeling of Eu bindings by deep groundwater humic substances

Terashima, Motoki; Saito, Takumi*; Iijima, Kazuki; Yui, Mikazu

no journal, , 

Investigation for colloids in the groundwater of Horonobe URL, 1; Characterization of colloids in the groundwater by using ultra filtration

Amano, Yuki; Amamiya, Hiroki; Murakami, Hiroaki; Iwatsuki, Teruki; Terashima, Motoki; Mizuno, Takashi; Kirishima, Akira*; Kuno, Atsushi*; Sasaki, Takayuki*; Kubota, Takumi*; et al.

no journal, , 

no abstracts in English

Assessing the effect of humic substances on migration of radionuclides in geological disposal system

Terashima, Motoki; Saito, Takumi*; Okazaki, Mitsuhiro*; Tachi, Yukio; Iijima, Kazuki

no journal, , 

no abstracts in English

Electrochemical study on the redox properties of humic substances from deep sedimentary groundwater

Saito, Takumi; Terashima, Motoki; Onuki, Toshihiko

no journal, , 

Redox properties of humic substances extracted from deep sedimentary groundwater was investigated by cyclic voltammetry and bulk electrolysis with a mediator organic molecule. Reversible current-potential curves were observed with the mediator, although electrode reaction of humic substances are slow in general. The redox capacities of various humic substances exhibited positive correlation with their aromaticity; those of deep groundwater humic substances were appreciably smaller than those of surface humic substances.

Ion-binding properties of humic substance in deep sedimentary groundwater

Saito, Takumi*; Terashima, Motoki

no journal, , 

Humic substances (HSs) are ubiquitous in various environments and play an important role for the fate of pollutants. Deep underground environment is not an exception, although physicochemical and ion-binding properties of HSs there are largely unknown due to difficulties of their extraction. Based on limited studies on deep underground HSs, it has been recognized that they are distinctive from their counterparts in surface or shallow sub-surface environments. Thus, we have been studying humic and fulvic acids extracted from sedimentary groundwater at -250 m below ground surface at the Horonobe underground research laboratory, JAEA, including their chemical compositions, size distributions, spectroscopic properties, and ion bindings. The aim of this talk is to demonstrate similarities and differences between the Horonobe HSs and surface HSs.

Characterization and determination of thermodynamic quantities of humic acid dissolved in deep groundwater at Horonobe, Hokkaido, Japan

Kimuro, Shingo*; Kirishima, Akira*; Akiyama, Daisuke*; Sato, Nobuaki*; Nagao, Seiya*; Saito, Takumi*; Amano, Yuki; Miyakawa, Kazuya; Terashima, Motoki

no journal, , 

no abstracts in English

Influence of deposition power and temperature on SiO/AlGaN interface property deposited by PECVD

Terashima, Daiki*; Watanabe, Kenta*; Yamada, Takahiro*; Nozaki, Mikito*; Shih, H.*; Nakazawa, Satoshi*; Anda, Yoshiharu*; Ueda, Tetsuzo*; Yoshigoe, Akitaka; Hosoi, Takuji*; et al.

no journal, , 

Impact of input power and substrate temperature of SiO deposition by plasma-enhanced CVD on SiO/AlGaN interface was investigated by means of electrical characterization of MOS capacitors. Synchrotron radiation photoemission spectroscopy revealed that Ga oxide component on AlGaN surface increases with increasing input power of PECVD. MOS capacitors with SiO gate insulator deposited at low input power shows relatively better SiO/AlGaN interface quality, despite degraded interface quality for the sample with SiO deposited at high input power. These results suggest that AlGaN surface oxidation during oxide deposition should be controlled to obtain good interface property.