Dynamic variations of the light-induced effects in a-Ge_xSe_100-x films: experiment and simulation

Abstract

Light-induced effects in aGe x Se 100-x chalcogenide glasses, i.e., photobleaching (PB), photodarkening (PD), and photoinduced structural transformations, have been investigated as a function of composition across the glass-forming region by an optical two-laser-beam technique, Raman analysis, and first-principles simulations. It was found that there is a critical concentration of Ge x≈30% that corresponds to the crossover from transient PB to the mixture of transient PD and metastable PB. At the microscopic level, this corresponds to the change in the photoexcitation process. At low-Ge concentration (<20%), it is governed by the lone pair (LP) excitation, which diminishes with an increase in Ge content, yielding Ge-Se bond breakage at x≈30%. Further, an increase in Ge concentration (x>30%) favors breakage of the Ge-Ge bonds upon photoexcitation and formation of light-induced 3D nanostructures. The bond conversion process is verified by Raman analysis.

Ultrafast light-induced softening of chalcogenide thin films above the rigidity percolation transition

“…After inserting these parameters into Eqn. [1], we found that RC is approximately 20 A o . In an earlier analysis, the effective mass approximation model indicated that the separation between the e-h pair is about 3 A o in the ground state [29].…”

“…The interplay between light-induced effects and network rigidity is a heavily debated topic in several areas of contemporary physics, including optics, photonics, and glass science [1][2][3].…”

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

“…Also for amorphous Ge-chalcogenide films, the excitation of lone-pair electrons causes structural change. 37 In the present study, a white light of xenon lamp is used and the bandgap itself is supposed to change by the addition of Ag in the AgGe-S system. 26 Therefore, we assume that the photo-induced fluidity occurred by the change of the bandgap and the supply of the subgap illumination from the white light of the xenon lamp.…”

Observation of photobleaching in Ge-deficient Ge16.8Se83.2 chalcogenide thin film with prolonged irradiation

“…Previously, Mishchenko et al . ascribed the increase in transient PD amplitude with increasing Ge content to the suppression of the concentration of Se lone pair states, and the final increase in the metastable PB amplitude to the increase in the number of the ETH bonds in Ge 36 Se 64 glasses 14 . In the present experiments, the amplitude of the transient PD increases with increasing irradiation power density as shown in Fig.…”

“…Mishchenko et al . observed dynamic variations of the photo-induced effects in amorphous Ge x Se 100-x films 14 , where a crossover from a transient PD to the mixture of transient PD and metastable PB was found at x = 30 at.%. A.R Barik et al .…”