Measurement of transient photo-induced changes in thin films at J-PARC; Time-resolved neutron reflectivity measurements of silver photo-diffusion into Ge-chalcogenide films

J-PARCでの光照射による過渡的変化の測定; Geカルコゲナイド薄膜への銀光拡散に関する時間分解中性子反射率測定

坂口 佳史*; 朝岡 秀人  ; 魚住 雄輝; 川北 至信  ; 伊藤 崇芳*; 久保田 正人 ; 山崎 大  ; 曽山 和彦  ; Ailavajhala, M.*; Wolf, K.*; Mitkova, M.*; Skoda, M. W. A.*

Sakaguchi, Yoshifumi*; Asaoka, Hidehito; Uozumi, Yuki; Kawakita, Yukinobu; Ito, Takayoshi*; Kubota, Masato; Yamazaki, Dai; Soyama, Kazuhiko; Ailavajhala, M.*; Wolf, K.*; Mitkova, M.*; Skoda, M. W. A.*

アモルファスGeカルコゲナイド/銀の界面において光を照射すると拡散が促進される。非破壊かつ時間分解で観測できるJ-PARC(写楽)の中性子反射率測定を用いて、光照射によってAgが、初期の急速な拡散によるAg-richな層の形成と、緩やかな拡散によるAg-poorな層の形成と、2段階のプロセスを経て拡散が進行していることを明らかにした。

We report recent results of time-resolved neutron reflectivity measurements for silver photo-diffusion into GeS (x=0.20, 0.33, 0.40) films performed on BL17 (SHARAKU). It is well known that silver diffuses into Ge-chalcogenide layer by visible light exposure with a distinct diffusion front, where the silver concentration abruptly drops off. Using an event recording system at the Materials and Life Science Experimental Facility, neutron reflectivity profiles were collected with a time-resolution of 30 seconds in the shortest case. It was found from the measurements that a relatively stable Ag-rich phase in the reaction layer is firstly formed, and then, slower diffusion occurs at the interface between Ag-rich and Ag-poor layers. Fourier transform analysis showed that the position of the interface is essentially fixed. This result is in contrast to the previously reported model of silver diffusion that postulates a mechanism involving progression of the diffusion front. The results of the measurements on Ag/Ge-Se films performed on the INTER instrument at ISIS are also reported.