Stretched exponential parameterization of in-situ photodarkening kinetics in amorphous As–Se films

The governed kinetics describing in-situ photodarkening in amorphous As100 − xSex films of different compositions (x = 40, 50, 60) and thicknesses (0.54–2.04 μm) were analyzed within stretched exponential parameterization algorithm. It was found that this kinetics strongly depended on penetration depth of pumping light. In case of films thicker than penetration depth, the governed kinetics attained a character stretched exponential behavior, while in thinner films (with thickness less than penetration depth) the stretched exponential relaxation tented towards single exponential one. These peculiarities were described in terms of photon-assisted site switching facilitating percolative growth of atomic clusters in the ground state activated under the influence of absorbed pumping light.

► Kinetics of in-situ photodarkening in As–Se films is non-dispersive in nature.
► Transition to stretched exponential kinetics depends on penetration depth of light.
► Fitting parameters of this kinetics are guided by film composition and thickness.