The effect of titanium doping on the structure and phase change characteristics of Sb₄Te

As a growth-dominated phase change material, Sb₄Te (ST) has fast crystallization speed while thermal stability is very poor, which makes it unsuitable for application in phase change random access memory (PCRAM). After doping Ti, the crystallization temperature is greatly improved to 210.33 °C, which is much higher than that of conventional Ge₂Sb ₂Te₅ (∼150 °C), and the melting point is reduced to 540.27 °C. In addition, grain size of crystalline Ti-doped Sb ₄Te (TST) film is significantly decreased to nanoscale. Ti atom is believed to occupy the lattice site of Sb atom in TST. With good thermal stability, TST-based PCRAM cell also has fast crystallization rate of 6 ns. Furthermore, the energy consumption is also lower than that of Ge ₂Sb₂Te₅-based one. Endurance of exceeding 2E5 cycles is obtained with a resistance ratio of one order of magnitude. Therefore, Ti doping seems to be a good way to solve the contradiction between thermal stability and fast crystallization speed of Sb-Te alloys.