Ge/Sb2Te3 nanocomposite multilayer films for high data retention phase-change random access memory application

The amorphous-to-crystalline transition of Ge/Sb2Te3 nanocomposite multilayer films with various thickness ratios of Ge to Sb2Te3 were investigated by utilizing in situ temperature-dependent film resistance measurements. The crystallization temperature and activation energy for the crystallization of the multilayer films increased with the increase in thickness ratio of Ge to Sb2Te3. The difference in sheet resistance between amorphous and crystalline states could reach as high as 104 Ω/□. The crystallization temperature and activation energy for the crystallization of Ge/Sb2Te3 nanocomposite multilayer films was proved to be larger than that of conventional Ge2Sb2Te5 film, which ensures a better data retention for phase-change random access memory (PCRAM) use. A data retention temperature for 10 years of the amorphous state [Ge (2 nm)/Sb2Te3 (3 nm)]40 film was estimated to be 165 °C. Transmission electron microscopy (TEM) images revealed that Ge/Sb2Te3 nanocomposite multilayer films had layered structures with clear interfaces.