Studies of silver photo diffusion dynamics in Ag/Ge
S
(
=0.2 and 0.4) films using neutron reflectometry
Sakaguchi, Yoshifumi*; Asaoka, Hidehito
; Uozumi, Yuki; Kawakita, Yukinobu
; Ito, Takayoshi*; Kubota, Masato
; Yamazaki, Dai
; Soyama, Kazuhiko
; Ailavajhala, M.*; Latif, R.*; Mitkova, M.*
We report our recent results of neutron reflectivity measurements for Ag/a-Ge
S
(x=0.2, 0.4) films under light illumination. The neutron reflectivity measurements have been performed on a polarized neutron reflectometer (BL17, SHARAKU) at Japan Proton Accelerator Research Complex (J-PARC), Japan. By using the time-of flight instrument with intensive pulsed neutrons produced by 300kW proton beams, time evolution of the neutron reflectivity under a light illumination has been revealed, with at least 2-min time resolution. From the detailed analysis, it was found for Ag 50nm/Ge
S
150nm films under a light illumination from the Ag layer side that there are two types of diffusion processes: a fast change observed in the first 10 min after illumination using a xenon lamp, which is then followed by a slow change observed after a 1 hour of additional light exposure. The result indicates that there is a comparatively stable (metastable) state in the Ag-doped Ge
S
layer in terms of Ag composition, and the next silver diffusion process occurs by affecting the Ag-doped Ge
S
layer / interface. This coincides with the Ge
S
results of Wagner et al. obtained for Ag/As-S films. These results are also in accord with the results reported by some of us by modeling of the Ag transport in Ge-Se glass showing the presence of slow and fast moving Ag ions. Our result demonstrated that the idea of a two-step reaction process can be applied to Ge-chalcogenide system. We also discuss illumination-side dependence and Ge-composition dependence of reaction process.