An optical study of the athermal photo-amorphization of As50Se50 thin films

In this paper we report on a study of a novel photo-induced structural effect in amorphous chalcogenide materials, namely the reversible and athermal light-induced vitrification of As50Se50 thin films. The first optical analysis of this phenomenon presented here was done by applying two different non-destructive methods. One is based on the optical transmittances of the interference maxima and minima at normal incidence, and takes into account the lack of thickness uniformity of the chalcogenide glass films. The other optical method, however, is based only on the shift undergone by the wavelengths of the interference extrema when the incidence changes from normal to oblique. On the other hand, the refractive-index behaviour of the as-evaporated, crystallized and photo-vitrified films under study is analyzed within the oscillator framework proposed by Wemple and DiDomenico. Finally, the absorption edge is described using the non-direct transition model proposed by Tauc.