Impact of post-nitridation annealing in CO ambient on threshold voltage stability in 4H-SiC metal-oxide-semiconductor field-effect transistors

Hosoi, Takuji*; Osako, Momoe*; Moges, K.*; Ito, Koji*; Kimoto, Tsunenobu*; Sometani, Mitsuru*; Okamoto, Mitsuo*; Yoshigoe, Akitaka; Shimura, Takayoshi*; Watanabe, Heiji*

Applied Physics Express, 15(6), p.061003_1 - 061003_5, 2022/06

https://doi.org/10.35848/1882-0786/ac6f42

The combination of NO annealing and subsequent post-nitridation annealing (PNA) in CO ambient for SiO/SiC structures has been demonstrated to be effective in obtaining both high channel mobility and superior threshold voltage stability in SiC-based metal-oxide-semiconductor field-effect transistors (MOSFETs). N atoms on the SiO side of the SiO/SiC interface incorporated by NO annealing, which are plausible cause of charge trapping sites, could be selectively removed by CO-PNA at 1300C without oxidizing the SiC. CO-PNA was also effective in compensating oxygen vacancies in SiO, resulting high immunity against both positive and negative bias-temperature stresses.

Characteristics of radiation-induced bystander effect; Participation of nitric oxide

Yokota, Yuichiro; Funayama, Tomoo; Ikeda, Hiroko; Kobayashi, Yasuhiko

Isotope News, (741), p.21 - 25, 2016/01

http://www.jrias.or.jp/books/pdf/201601_TENBO_YOKOTA_HOKA.pdf

Our article published on the International Journal of Radiation Biology (2015) was reviewed. We investigated the dependence of the bystander cell-killing effect on radiation dose and quality, and related molecular mechanisms. Human fibroblasts were irradiated with -rays or carbon ions and co-cultured with non-irradiated cells. Survival rates of non-irradiated cells decreased and nitrite concentrations in co-culture medium increased with dose. Their dose responses were similar between -rays and carbon ions. Treatment of the specific nitric oxide (NO) radical scavenger prevented reductions in survival rates of non-irradiated cells. Negative relationships were observed between survival rates and nitrite concentrations. From these results, it was concluded that the bystander cell-killing effect mediated by NO radicals depends on irradiation doses, but not on radiation quality. NO radical production appears to be an important determinant of bystander effects.

Bystander effect mediated by nitric oxide depends on irradiation dose but not on radiation quality

Yokota, Yuichiro; Funayama, Tomoo; Ikeda, Hiroko; Sakashita, Tetsuya; Suzuki, Michiyo; Kobayashi, Yasuhiko

JAEA-Review 2014-050, JAEA Takasaki Annual Report 2013, P. 75, 2015/03

https://doi.org/10.11484/jaea-review-2014-050

We investigated the bystander effect induced by -rays or carbon ions and analyzed the role of nitric oxide (NO) in the effect. Normal human fibroblasts were used. Cells inoculated on a porous membrane were irradiated with varying doses of -rays or carbon ions. Irradiated cells were then non-contact co-cultured with non-irradiated cells for 24 h. After co-culture, the survival rates of non-irradiated bystander cells co-cultured with irradiated cells decreased with increasing dose and bottomed out at 0.5 Gy or higher doses. This indicates that the bystander effect is dependent on irradiation dose but independent of radiation quality. Next, a specific NO scavenger c-PTIO was added to the culture medium during irradiation and co-culture. This treatment prevented the reduction in survival rates of bystander cells, clearly indicating that NO has an important role in the bystander effect.

None

Endo, Hideo; ; ; ; ; Nagai, Shuichiro

PNC TN8410 93-065, 192 Pages, 1993/04

PNC-TN8410-93-065.pdf:4.77MB

None

Bystander cell-killing effect mediated by nitric oxide in normal human fibroblasts depends in part on irradiation dose but not on radiation quality

Yokota, Yuichiro; Funayama, Tomoo; Ikeda, Hiroko; Kobayashi, Yasuhiko

no journal, , 

To get the whole picture of bystander effects is necessary to better understand the effect of low-dose irradiation. Normal human fibroblasts were irradiated with carbon ions or rays. After irradiation, irradiated and non-irradiated cells were co-cultured in the upper and lower parts of porous membrane, respectively. The survival rates of bystander cells decreased with dose and bottomed out at around 80%. In addition, the survival rates of bystander cells were not different between carbon ions and rays at the same doses. These indicate that the bystander effect depends in part on irradiation dose but not on radiation quality. Treatment of a specific scavenger of nitric oxides suppressed the reduction of survival rates of bystander cells. There were also negative relationships between the survival rates of bystander cells and the nitrite concentrations of the medium, suggesting that the amounts of nitric oxide released are an important factor related to the bystander effect.

Analysis of medium-mediated bystander effects induced by carbon-ion irradiation between human lung normal and cancer cells

Ikeda, Hiroko; Yokota, Yuichiro; Funayama, Tomoo; Kanai, Tatsuaki*; Nakano, Takashi*; Kobayashi, Yasuhiko

no journal, , 

In this study, human lung normal fibroblasts WI-38 and human lung cancer cells H1299/wt were used. Cells were irradiated with carbon-ion broad beams, then survival rates of bystander cells after co-culture with irradiated cells were measured using colony assay. The survival rates of non-irradiated bystander cancer cells co-cultured with 0.13 Gy irradiated normal cells increased after 6-hours co-culture. On the other hand, the bystander cells co-cultured with 0.5 Gy irradiated normal cells showed decreased survival rates. These results indicated that the bystander responses of the cancer cells changes according to the irradiation dose on the normal cells. In addition, the survival rates of bystander cancer cells showed a tendency to increase by the addition of Carboxy-PTIO to the co-culture medium, when co-cultured with 0.5 Gy irradiated normal cells. From these results, reduction of survival rates is likely to be caused by NO radical as a mediator in bystander effects.

Radiation quality-independent bystander effect and its molecular mechanism

Yokota, Yuichiro; Funayama, Tomoo; Ikeda, Hiroko; Muto, Yasuko*; Suzuki, Michiyo; Sakashita, Tetsuya; Kobayashi, Yasuhiko

no journal, , 

We investigated the influence of irradiated dose and radiation quality on bystander effect. Human normal fibroblasts were irradiated with carbon-ion beam and -rays, and then co-cultured with non-irradiated cells. Following co-culture for 24 h with or without c-PTIO, a scavenger of nitric oxide (NO), the survival rates of non-irradiated cells and the concentrations of nitrite, an oxide of NO, in the co-culture medium were measured. Survival of the non-irradiated cells decreased with increasing dose and reached around 80% at 0.5 Gy. The dose-response curves were similar between carbon-ion beam and -rays, indicating the bystander effect depended on dose but not on radiation quality. c-PTIO suppressed reduction of survival rates of the non-irradiated cells. Furthermore, there were negative relationships between survival rates of the non-irradiated cells and nitrite concentrations. In summary, the amounts of produced NO might be a determinant of the bystander effect.