first principles investigation

Among phase change materials based on Ge, Sb, and Te, Sb₂Te₃ (ST) has been paid attention to due to its faster operation speed and lower power consumption than Ge₂Sb₂Te₅. However, its poor stability prevents its application to commercial memory devices. As a solution to resolve such poor stability issue while maintaining its advantages, various doping conditions has been proposed that would provide significant improvement in phase change characteristics including enhanced thermal stability and lowered operation energy. Using first-principles density functional calculations, we investigate the effects of several dopants such as Ti, C, and Se on the phase change properties of ST. First, we identify preferred sites of dopants in ST by evaluating and comparing their formation energies. Then we explore the modification of bonding characters of ST due to dopants to understand the roles of dopants in the enhancement of the phase change characteristics. Our study suggests that Sb₂Te₃ under certain doping conditions would have sufficient potential for practical phase-change memory devices with high stability and fast operation speed