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/TiO_x 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.