Understanding the role of Zn in improving the phase change behaviors of Sb2Te3 films

The Zn-doped Sb2Te3 films have been investigated systematically during the phase transformation process. It was found that, the increase of crystallization temperature in the Zn-doped Sb2Te3 films leads to its enhanced amorphous stability, and Zn incorporation can increase electrical resistance, widen optical band gap and refine crystalline grain size. The crystallization mechanism can be tuned into nucleation-dominated from growth-dominated type. Moreover, Sb2Te3 film with high Zn-doping concentration such as Zn38.8(Sb2Te3)61.2 film was found to exhibit a higher crystallization temperature (233 °C), better data retention ability (keeping the amorphous state at 146.5 °C for ten years), and wider band gap (0.839 eV). A lower threshold of crystallization (~ 25 ns) can be realized in the Zn38.8(Sb2Te3)61.2 film irradiated at the laser power of 70 mW in comparison with that in the conventional Ge2Sb2Te5 film. We confirm that the Zn doping is responsible for a fast switching and the Zn38.8(Sb2Te3)61.2 compound is stable against segregation with cycling.