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

Abstract

Silver diffuses into chalcogenide films upon light exposure, and the kinetics of photodiffusion has been a subject of various investigations because of the difficulties in the in situ determination of the time-dependent Ag reaction and diffusion development in the chalcogenide layers. In this paper, we report the results of time-resolved neutron reflectivity measurement of Ag/Ge 40 S 60 /Si substrates under light exposure to clarify the kinetics of Ag photodiffusion into Ge-rich Ge chalcogenides. It reveals that Ag ions diffuse all over the Ge chalcogenide host layer once Ag dissolves into the layer without forming a metastable reaction layer unlike the case of S-rich Ge chalcogenide such as Ge 20 S 80. The decay curve suggests that the Ag dissolution is determined by two types of Ag capturing chalcogen sites. Also, the observed relaxation time showed anomalous chalcogenide layer thickness dependence. This is attributed to an additional diffusion-driven accelerating factor, which is unique to the silver photodiffusion. Furthermore, we observed indicative changes in the formation of an inhomogeneous in-plane structure at the Ag/chalcogenide interface. This would be related to the nucleation and growth of the Ag-dissolved reaction product.

Kinetics of Silver Photodiffusion Into Amorphous Ge20S80 Films: Case of Pre‐Reaction

“…As for the peak of Ag (111) at 38.1°, its intensity decreases with increasing the chalcogenide layer thickness from 450 to 775 Å. This is consistent with our previous experiment on the chalcogenide thickness dependence and with the intercalation model proposed by Kluge, suggesting that more silver dissolves into the thicker chalcogenide layer. According to the model, intercalation of Ag occurs by the creation of Ch − Ag + bonds (Ch: chalcogen atom) at the site of the Ch‐Ch or Ge‐Ch bond.…”

“…In Ge 33 S 67 /Ag/Si substrate and Ag/Ge 40 S 60 /Si substrate, Ag ions dissolve into the chalcogenide layer and immediately diffuse all over the layer upon the light exposure, without forming a metastable layer between the Ag layer and the chalcogenide layer . Also, the reaction rate shows anomalous chalcogenide thickness dependence, which is considered to occur due to a diffusion‐driven accelerating factor in the reaction rate . The chalcogenide thickness dependence on the reaction rate was observed in Ge 33 S 67 /Ag/Si substrate and Ag/Ge 40 S 60 /Si substrate.…”

“…On the other hand, use of neutron beam is safer to eliminate possible changes by the probe beam itself. Recently, we focused on neutron reflectivity and the technique was applied to the investigations on silver photo‐diffusion into Ge chalcogenide . It was found from these measurements that the kinetics of the silver photo‐diffusion markedly depends on the Ge composition in amorphous germanium sulfide.…”

“…In Ag 500 Å/Ge 20 S 80 /Si substrate, Ag dissolution occurs in the first 2 min, forming a metastable Ag‐rich reaction layer between the Ag layer and the Ge 20 S 80 layer, and a subsequent slow Ag diffusion occurs from the metastable layer to the Ge 20 S 80 host layer in the next 20 min . In Ge 33 S 67 /Ag/Si substrate and Ag/Ge 40 S 60 /Si substrate, Ag ions dissolve into the chalcogenide layer and immediately diffuse all over the layer upon the light exposure, without forming a metastable layer between the Ag layer and the chalcogenide layer . Also, the reaction rate shows anomalous chalcogenide thickness dependence, which is considered to occur due to a diffusion‐driven accelerating factor in the reaction rate .…”

Плазмон-стимулированное фотолегирование в тонкослойной структуре As-=SUB=-2-=/SUB=-S-=SUB=-3-=/SUB=---Ag

“…Фотостимулированное взаимодействие в тонкопленочной структуре ХС−Ag является сложным явлением, включающим фотоэлектрические процессы, фотостимулированный массоперенос, химическое взаимодействие диффундирующих компонентов [10,11]. Эта сложность процесса обусловила и разную терминологию, которая применялась в литературе для данного явления, в частности, фотолегирование (photodoping) [10,12], фотодиффузия [11,13], фоторастворение [14]. Каждый из этих терминов отражает определенные особенности процесса и все они могут использоваться как синонимы.…”