Laser-induced amorphous-to-crystalline phase transition in SbxSe1−x alloys

Laser-induced transitory changes in the optical properties (photodarkening) and a phase transformation to crystalline modification (photocrystallization) were studied in amorphous selenium (a-Se) containing relatively small amounts (≤5 at.%) of antimony additives. It was shown that the photoeffects observed critically depends on exposure (intensity) and exhibit threshold behavior. At low values of illumination intensity, the observed behavior is attributed to an alteration of structural defect states giving rise to deep levels in mobility gap. On the contrary, when the irradiation intensity is more than the threshold value photoinduced crystallization takes place. The origin of these different phenomena is discussed on the basis of microcrystalline model.