Dynamics of silver photo-diffusion into Ge-chalcogenide films; Time-resolved neutron reflectometry

時間分解中性子反射率によるGeカルコゲナイド薄膜への銀光拡散

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.*; Latif, M. R.*; 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.*; Latif, M. R.*; 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)とISIS(INTER)の中性子反射率測定を用いて、拡散界面の解析を行った。その結果、光照射によって初期の急速なAg拡散によるAg-rich層の形成された後、その界面をほぼ一定に保ちながら、緩やかな拡散による第2のAg-poor層が形成される2段階のプロセスが進行していることが明らかになった。

We report the results of time-resolved neutron reflectivity measurements of Ag/a- GeS/Si and a- GeSe/Ag/ Si films taken while the films are exposed to visible light. Silver diffuses into an amorphous (a-) chalcogenide layer while visible light illuminates Ag/a-chalcogenide films. Neutron reflectometry is a suitable technique probing time evolution of the multi-layer structure without damaging the sample by the probe beam itself. It was found from the measurements of Ag/a-GeS/Si films that a relatively stable Ag-rich phase in the reaction layer is first formed, and then, slower diffusion occurs at the interface between Ag-rich and Ag-poor layers. This result is in contrast to the previously reported model of silver diffusion that suggests a mechanism involving progression of the diffusion front. From the measurements of a-GeSe/Ag/ Si films, we found enormous changes in the neutron reflectivity profile, including loss of total reflection region, with continuous illumination even after forming one homogeneous layer, which was about 60 min after starting illumination. At this stage, clear off-specular scattering was observed by a linear detector and a surface roughness was observed with naked eyes.