Doping effects of Ru on Sb2Te and Sb2Te3 as phase change materials studied by first-principles calculations

In order to meet the requirements of phase change random access memory (PCRAM) for re-writing capability, stability and crystallization rate, phase change materials (PCMs) need to be optimized and modified. In the previous experimental work, we found that Ru doping can significantly improve the stability and reading/writing speed of Sb2Te and Sb2Te3. In order to clarify the underlying physical mechanism of Ru doping effects on the improvement of PCRAM performance of Sb2Te and Sb2Te3, in this work, we further used the First-principles method to systematically calculate and analyze the crystal microstructure and electronic structure of Rudoped Sb2Te and Sb2Te3. In the crystal of Sb2Te and Sb2Te3, the substitution doping of Ru occupying the Sb site inside the [Sb2Te3] penta-atomic layer is the most stable. Ru forms strong covalent bonds with Sb and Te in the matrix, which can improve the structural stability and crystallization temperature. The substitution doping of Ru at Sb site increases the band gap and carrier effective mass of Sb2Te and Sb2Te3, resulting in the increase of their resistivity. At the same time, this doping mode can also maintain the excellent rapid reversible phase transition properties of Sb2Te and Sb2Te3.