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

Abstract

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 Ge 33 S 67 /Ag/Si substrate stacks change under light exposure in the depth by measuring timeresolved neutron reflectivity. It was found from the measurement that Ag ions diffuse all over the matrix Ge 33 S 67 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. Published by AIP Publishing. [http://dx

Silver photodiffusion into Ge-rich amorphous germanium sulfide—neutron reflectivity study

“…This means that the Ag ions immediately diffuse all over the Ch host layer once they dissolve into the Ch host layer upon light exposure. This diffusion process is the same as that of the stoichiometric Ge 33 S 67 /Ag/Si substrate, 29 and is in contrast to the S-rich case of Ag/Ge 20 S 80 (Ref. 25) and Ag/Ge 25 S 75 .…”

“…Therefore, we expect that Ag can dissolve into the Ch host layer by 8.9% by more extended light exposure. In our previous study on the Ge 33 S 67 /Ag/Si substrate, 29 the saturated content of Ag was estimated to be 20% (Ag 0.20 Ge 0.27 S 0.53 ). Kawaguchi and Maruno 10 also demonstrated that the total amount of photodoped Ag for Ag/Ge 33 S 67 is about twice that of Ag/Ge 40 S 60 .…”

“…A detailed measurement and analysis of the stoichiometric composition, Ge 33 S 67 /Ag/Si substrates, revealed the time variation of the thicknesses of Ag and the reaction layers, and a clear Ch layer thickness dependence on the silver diffusion was found from the study. 29 In this paper, we focus on a Ge-rich compound, which is considered to show different behavior from the stoichiometric composition, and report the detailed results of neutron reflectivity measurements of Ag/Ge 40 S 60 /Si substrate films. In addition, we discuss the mechanism of silver photodiffusion into the Ge-rich compound layer, based on the experimental result.…”

“…In addition, it was found from the present study and the previous study on Ge 33 S 67 /Ag that more Ag ions can dissolve into the thicker Ch layer. 29 Considering the compositional dependence and the Ch layer thickness dependence, the content of dissolved Ag ions seems to be determined by the content of sulfur atoms. This is consistent with the intercalation model, proposed by Kluge.…”

“…However, silver diffusion can also be induced by a strong X-ray beam, 24 and the use of neutron beams is considered safer. Recently, we performed neutron reflectivity measurements of Ag/Ge chalcogenide films [25][26][27][28][29] and found that this technique is quite useful to observe the time-dependent changes in the films in the depth direction without inducing the silver diffusion by the probe beam itself. From the preliminary results of the Ag/Ge 20 S 80 /Si substrate, the Ag/Ge 25 S 75 /Si substrate, and the a)…”