Stimulated Surface Relief Erasing in Amorphous As-Se Layers: Thermal- and Light Induced Effects

Here the kinetics of erasing surface relief gratings (SRGs) in amorphous As₂₀Se₈₀ thin films are studied under various temperatures (in the range 298–408 K) and continuous-wave illumination by band gap light of various intensities (0–2.5 W cm⁻²) and polarizations. The SRGs with 3.5 and 15 μm periods and 300 nm amplitudes are recorded by two beam interference. By the measurements of erasing kinetics on the grating of two the different periods, the authors are able to separate contributions of viscous flow and photo-induced (PI) diffusion flow, which the authors consider as independent mechanisms of mass transfer. The authors detect that band gap light illumination does not change the viscosity of chalcogenide films. In contrast to previous results, the authors suggest that mass transport is accelerated by light due to contribution of PI diffusion flow, not by decrease of “pure” viscous flow. Contribution of PI diffusion flow, as well as anisotropy of mass transport under illumination by polarized light, drops with increasing temperature, whereas contribution of viscous flow grows with temperature. By separation of contributions of PI diffusion and viscous flow in mass transfer, the authors can determine PI diffusion coefficients and their temperature dependences.