Electron Microscopic Study of the Influence of Annealing on Ge–Sb–Te Thin Films Obtained by Vacuum Thermal Evaporation

Abstract

Using transmission electron microscopy it is demonstrated that the annealing of amorphous Ge₂Sb₂Te₅ films deposited by vacuum thermal evaporation at 250°C leads to the formation of a hexagonal phase with a peculiar block structure. Herewith, island defects are formed on their surface representing the cubic modification of Sb₂O₃. The sizes of these defects and portion of the surface area occupied by them are estimated using images of scanning electron microscopy. The formation of antimony-oxide crystallites can be attributed to enrichment of the surface area of the initial film with antimony which is oxidized during annealing. Due to the formation of defects, the film composition in adjacent local areas varies and becomes close to the stoichiometric values for Ge₃Sb₂Te₆.