Yuki Uozumi

Silver photo-diffusion and photo-induced macroscopic surface deformation of Ge33S67/Ag/Si substrate

Ge-chalcogenide films show various photo-induced changes, and silver photo-diffusion is one of them which attracts lots of interest. In this paper, we report how silver and Ge-chalcogenide layers in Ge33S67/Ag/Si substrate stacks change under light exposure in the depth by measuring time-resolved neutron reflectivity. It was found from the measurement that Ag ions diffuse all over the matrix Ge33S67 layer once Ag dissolves into the layer. We also found that the surface was macroscopically deformed by the extended light exposure. Its structural origin was investigated by a scanning electron microscopy.

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

Study on photo-induced changes for specific light-sensitive materials is fascinating from both academic and application points of view because it is one of the frontiers in materials science including concepts of electron-excitation and non-equilibrium state, and the materials can be controlled spatially by illuminated area from distant place [1]. With the aid of significant development of light source equipment such as femtosecond ultra-short pulsed laser systems, attractive photo-induced phenomena have been found in many materials in these days. In the leading-edge field, it is quite natural to be interested in finding the structural origin of the photo-induced changes. Although neutron scattering technique has always a difficulty in beam intensity, it is highly expected to be utilized in structural determination for magnetic materials, hydrogenated materials, and X-ray sensitive materials. At the Materials and Life Science Experimental Facility (MLF) of the Japan Proton Accelerator Research Complex (J-PARC), the proton beam intensity is now 300kW, and it is planned to go to 1MW in