| Summary: | As a new generation of non-volatile memory, phase change random access memory (PCRAM) has the potential to fill the hierarchical gap between DRAM and NAND FLASH in computer storage. Sb<sub>2</sub>Te<sub>3</sub>, one of the candidate materials for high-speed PCRAM, has high crystallization speed and poor thermal stability. In this work, we investigated the effect of carbon doping on Sb<sub>2</sub>Te<sub>3</sub>. It was found that the FCC phase of C-doped Sb<sub>2</sub>Te<sub>3</sub> appeared at 200 °C and began to transform into the HEX phase at 25 °C, which is different from the previous reports where no FCC phase was observed in C-Sb<sub>2</sub>Te<sub>3</sub>. Based on the experimental observation and first-principles density functional theory calculation, it is found that the formation energy of FCC-Sb<sub>2</sub>Te<sub>3</sub> structure decreases gradually with the increase in C doping concentration. Moreover, doped C atoms tend to form C molecular clusters in sp<sup>2</sup> hybridization at the grain boundary of Sb<sub>2</sub>Te<sub>3</sub>, which is similar to the layered structure of graphite. And after doping C atoms, the thermal stability of Sb<sub>2</sub>Te<sub>3</sub> is improved. We have fabricated the PCRAM device cell array of a C-Sb<sub>2</sub>Te<sub>3</sub> alloy, which has an operating speed of 5 ns, a high thermal stability (10-year data retention temperature 138.1 °C), a low device power consumption (0.57 pJ), a continuously adjustable resistance value, and a very low resistance drift coefficient.
|
|---|