Controllable crystal growth and fast reversible crystallization-to-amorphization in Sb2Te-TiO2 films

The structure evolution and crystallization processes of Sb2Te-TiO2 films have been investigated. The Sb2Te-rich nanocrystals, surrounded by TiO2 amorphous phases, are observed in the annealed Sb2Te-TiO2 composite films. The segregated domains exhibit obvious chalcogenide/TiOx interfaces, which elevate crystallization temperature, impede the grain growth and increase crystalline resistance. Compared with that in conventional Ge2Sb2Te5 film, the shorter time for onset crystallization (25 ns) and amorphization (100 ns) has been achieved in as-deposited (Sb2Te)94.7(TiO2)5.3 film under 60 mW laser irradiation. The corresponding recrystallization and re-amorphization can also be realized in the film. From Johnson-Mehl-Avrami (JMA) analysis, it is further found that the one-dimensional grain growth with controlled interface is dominant for the film during the fast phase-change process. Therefore, (Sb2Te)94.7(TiO2)5.3 film with improved crystallization mechanism is promising for high-stable and fast-speed memory applications.