Sb-rich Si-Sb-Te phase change material for multilevel data storage: The degree of disorder in the crystalline state

The phase change memory with monolayer chalcogenide film (Si ₁₈Sb₅₂Te₃₀) is investigated for the feasibility of multilevel data storage. During the annealing of the film, a relatively stable intermediate resistance can be obtained at an appropriate heating rate. The transmission electron microscopy in situ analysis reveals a conversion of crystallization mechanism from nucleation to crystal growth, which leads a continuous reduction in the degree of disorder. It is indicated from the electrical properties of the devices that the fall edge of the voltage pulse is the critical factor that determines a reliable triple-level resistance state of the phase change memory cell.