Yttrium-Doped Sb2Te3: A Promising Material for Phase-Change Memory.

Sb2Te3 exhibits outstanding performance among the candidate materials for phase-change memory; nevertheless, its low electrical resistivity and thermal stability hinder its practical application. Hence, numerous studies have been carried out to search suitable dopants to improve the performance; however, the explored dopants always cause phase separation and thus drastically reduce the reliability of phase-change memory. In this work, on the basis of ab initio calculations, we have identified yttrium (Y) as an optimal dopant for Sb2Te3, which overcomes the phase separation problem and significantly increases the resistivity of crystalline state by at least double that of Sb2Te3. The good phase stability of crystalline Y-doped Sb2Te3 (YST) is attributed to the same crystal structure between Y2Te3 and Sb2Te3 as well as their tiny lattice mismatch of only ∼1.1%. The significant increase in resistivity of c-YST is understood by our findings that Y can dramatically increase the carrier's effective mass by regulating the band structure and can also reduce the intrinsic carrier density by suppressing the formation of SbTe antisite defects. Y doping can also improve the thermal stability of amorphous YST based on our ab initio molecular dynamics simulations, which is attributed to the stronger interactions between Y and Te than that of Sb and Te.