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Journal Articles

Mass transport in the PdCu phase structures during hydrogen adsorption and absorption studied by XPS under hydrogen atmosphere

Tang, J.*; Yamamoto, Susumu*; Koitaya, Takanori*; Yoshigoe, Akitaka; Tokunaga, Takuma*; Mukai, Kozo*; Matsuda, Iwao*; Yoshinobu, Jun*

Applied Surface Science, 480, p.419 - 426, 2019/06

 Times Cited Count:2 Percentile:22.92(Chemistry, Physical)

Mass transports during hydrogen adsorption and absorption processes of PdCu alloys that has advantages of higher hydrogen diffusivity and economically lower-cost than the other Pd-alloys were studied. The research was made with a comparison of the well-known ordered phase of the bcc structure (the B2 phase) and a mixed phase of the fcc and B2 structures. ${it In-situ}$ ultrahigh vacuum X-ray photoelectron spectroscopy and ambient pressure X-ray photoelectron spectroscopy using synchrotron radiation were carried out to trace the chemical states of the Pd and Cu atoms as a function of temperatures. It is elucidated that the initial adsorption and absorption processes were similar in the two phases, but a hydrogen diffusion rate to the bulk was higher in the ordered phase than in the mixed one. We found the dynamics of the Pd and Cu atoms during the hydrogen adsorption/absorption processes largely depend on temperature. In the hydrogen atmosphere, the Pd atoms segregate at the surface below 373 K and Cu atoms segregate at the surface above 373 K. The present results agree well with the previous theoretical calculations and, thus, provide appropriate inputs toward developments of the hydrogen permeation materials.

Journal Articles

Radiation response of silicon carbide metal-oxide-semiconductor transistors in high dose region

Oshima, Takeshi; Yokoseki, Takashi; Murata, Koichi; Matsuda, Takuma; Mitomo, Satoshi; Abe, Hiroshi; Makino, Takahiro; Onoda, Shinobu; Hijikata, Yasuto*; Tanaka, Yuki*; et al.

Japanese Journal of Applied Physics, 55(1S), p.01AD01_1 - 01AD01_4, 2016/01

 Times Cited Count:10 Percentile:49.94(Physics, Applied)

Journal Articles

A Development of super radiation-hardened power electronics using silicon carbide semiconductors; Toward MGy-class radiation resistivity

Hijikata, Yasuto*; Mitomo, Satoshi*; Matsuda, Takuma*; Murata, Koichi*; Yokoseki, Takashi*; Makino, Takahiro; Takeyama, Akinori; Onoda, Shinobu; Okubo, Shuichi*; Tanaka, Yuki*; et al.

Proceedings of 11th International Workshop on Radiation Effects on Semiconductor Devices for Space Applications (RASEDA-11) (Internet), p.130 - 133, 2015/11

Journal Articles

Effect of humidity and temperature on the radiation response of SiC MOSFETs

Takeyama, Akinori; Matsuda, Takuma; Yokoseki, Takashi; Mitomo, Satoshi; Murata, Koichi; Makino, Takahiro; Onoda, Shinobu; Tanaka, Yuki*; Kandori, Mikio*; Yoshie, Toru*; et al.

Proceedings of 11th International Workshop on Radiation Effects on Semiconductor Devices for Space Applications (RASEDA-11) (Internet), p.134 - 137, 2015/11

Oral presentation

$$gamma$$-ray irradiation effect on SiC MOSFETs with gate-bias voltage

Murata, Koichi; Mitomo, Satoshi; Matsuda, Takuma; Yokoseki, Takashi; Makino, Takahiro; Abe, Hiroshi; Onoda, Shinobu; Okubo, Shuichi*; Tanaka, Yuki*; Kandori, Mikio*; et al.

no journal, , 

no abstracts in English

Oral presentation

The Electrical characteristics of SiC-MOSFETs irradiated with $$gamma$$-rays at elevated temperature

Matsuda, Takuma; Yokoseki, Takashi; Mitomo, Satoshi; Murata, Koichi; Makino, Takahiro; Abe, Hiroshi; Onoda, Shinobu; Okubo, Shuichi*; Tanaka, Yuki*; Kandori, Mikio*; et al.

no journal, , 

no abstracts in English

Oral presentation

Difference by the oxide fabrication process of the $$gamma$$-ray irradiation effect on SiC-MOSFET

Mitomo, Satoshi*; Matsuda, Takuma*; Murata, Koichi*; Yokoseki, Takashi; Makino, Takahiro; Abe, Hiroshi; Onoda, Shinobu; Oshima, Takeshi; Okubo, Shuichi*; Tanaka, Yuki*; et al.

no journal, , 

no abstracts in English

Oral presentation

Electrical properties of SiC MOSFETs irradiated with $$gamma$$-rays at elevated temperature

Matsuda, Takuma; Yokoseki, Takashi; Mitomo, Satoshi; Murata, Koichi; Makino, Takahiro; Takeyama, Akinori; Onoda, Shinobu; Okubo, Shuichi*; Tanaka, Yuki*; Kandori, Mikio*; et al.

no journal, , 

Silicon carbide (SiC) is expected to be applied to Metal-Oxide-Semiconductor (MOS) FETs used in harsh radiation environments to decommission TEPCO Fukushima Daiichi nuclear reactors. To develop radiation resistant SiC MOS FETs, clarification of their radiation response under elevated temperature is required. We measured capacitance-voltage (C-V) characteristics of SiC MOSFETs irradiated with $$gamma$$-rays at 423 K in nitrogen atmosphere. The samples were vertical power 4H-SiC MOSFETs with the blocking voltage of 1200 V and the rated current of 20 A with the gate oxide thickness of 45 nm. Typical C-V curve of a SiC MOSFET irradiated even up to 5 kGy was shifted to negative voltage side, suggesting that the positive charges generated in gate oxide by irradiation. While, no significant change in the slope of the curve was observed, indicating that interface traps between the gate oxide and SiC were merely generated. The radiation response of SiC MOS FETs under elevated temperature predominantly depends on the amount of positive charges generated in the gate oxide.

Oral presentation

Influence of $$gamma$$-ray irradiation under high temperature and humidity circumstance on the electrical characteristics of SiC MOSFETs

Takeyama, Akinori; Matsuda, Takuma; Yokoseki, Takashi; Mitomo, Satoshi; Murata, Koichi; Makino, Takahiro; Onoda, Shinobu; Okubo, Shuichi*; Tanaka, Yuki*; Kandori, Mikio*; et al.

no journal, , 

no abstracts in English

Oral presentation

Effect of high temperature and humidity on dose dependence of charges generated in SiC MOSFETs due to $$gamma$$-ray irradiation

Takeyama, Akinori; Matsuda, Takuma*; Yokoseki, Takashi*; Mitomo, Satoshi*; Murata, Koichi*; Makino, Takahiro; Onoda, Shinobu; Okubo, Shuichi*; Tanaka, Yuki*; Kandori, Mikio*; et al.

no journal, , 

Effect of $$gamma$$-ray irradiation under high temperature and humidity circumstances on the electrical characteristics of Silicon Carbide (SiC) Metal-Oxide-Semiconductor Field Effect Transistors (MOSFETs) was investigated. In the case of irradiation under high humidity circumstance, trapped oxide and interface charges densities generated due to irradiation were smaller than those for irradiation in dry circumstance. It is concluded that humidity circumstance suppressed the degradation of the electrical properties due to irradiation including threshold voltage shift and leakage current.

Oral presentation

Optimum structures for $$gamma$$-ray radiation resistant SiC-MOSFETs

Takeyama, Akinori; Mitomo, Satoshi*; Matsuda, Takuma*; Murata, Koichi*; Yokoseki, Takashi*; Makino, Takahiro; Onoda, Shinobu; Oshima, Takeshi; Okubo, Shuichi*; Tanaka, Yuki*; et al.

no journal, , 

Oxide thickness dependence of $$gamma$$-ray irradiation response on Silicon Carbide (SiC) Metal-Oxide-Semiconductor Field Effect Transistors (MOSFETs) was investigated. As a result of irradiation, the threshold voltage V$$_{th}$$ for both SiC MOSFETs with gate oxide of 30 nm or 60 nm thick shifted to negative voltage-side gently. However, the V$$_{th}$$ for 60 nm thick more immediately decreased over 400 kGy. It is found that SiCMOSFETs with smaller thickness has a higher radiation tolerance.

Oral presentation

Influence of gate bias on $$gamma$$-ray radiation response of SiC MOSFETs

Takeyama, Akinori; Murata, Koichi*; Mitomo, Satoshi*; Matsuda, Takuma*; Yokoseki, Takashi*; Makino, Takahiro; Onoda, Shinobu; Okubo, Shuichi*; Tanaka, Yuki*; Kandori, Mikio*; et al.

no journal, , 

Deterioration of electrical property of SiCMOSFETs due to irradiation was reduced compared with no biased ones, when the SiC MOSFETs with switching bias were irradiated. In order to clarify this mechanism, SiCMOSFETs were irradiated up to 50 kGy with switching bias applied to gate oxide from 4.5 to 0 V. As a result, the large negative shift of threshold voltage V$$_{th}$$ due to irradiation with positive bias significantly recovered in the cases that the bias switched to zero. It shows electrical property of SiCMOSFETs were immediately relieved when applied bias was removed by switching.

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