Transmission electron microscopy study of amorphous Ge ₂ Sb ₂ Te ₅ films induced by an ultraviolet single-pulse laser

Crystallization behaviors of α-GST films with the thickness of 80 and 30 nm induced by an ultraviolet pulse laser were investigated by using TEM integrated with SAED. Firstly, crystalline phase morphologies were shown and analyzed. Both plate grains and spherical grains were found for 80 nm thick film, while only plate grains were found for 30 nm thick film. Then the relationship between the grain size and laser fluence for the 80 nm thick film was studied and the effects of film thickness on crystallization morphology were analyzed. Finally a crystallization process model based on the relationship of the crystallization starting temperature and heating temperature was constructed to elucidate how the solid-phase crystallization and melt-cooling crystallization occurred and developed. It also unified the crystallization starting temperature under static conditions and the crystallization starting temperature under laser inducing conditions.