Ultra-low Energy Phase Change Memory with Improved Thermal Stability by Tailoring the Local Structure through Ag Doping

Abstract

Although Sb₂Te₃, as a candidate material for next-generation memory devices, has attractive properties such as higher operation speed and lower power consumption than Ge₂Sb₂Te₅, its poor stability prevents its application to commercial memory devices. Transition metal dopants provide enhancements in its phase change characteristics, improving both thermal stability and operation energy. However, the enhancement mechanism remains to be sufficiently investigated, and standard properties need to be achieved. Herein, the phase change properties of Sb₂Te₃ are confirmed to be enhanced by the incorporation of a heavy transition metal element such as Ag. The crystallization temperature increases by nearly 40%, and the operation energy is reduced by approximately 60%. These enhancements are associated with the changes in the local Sb₂Te₃ structure caused by Ag incorporation. As the incorporated Ag atoms substitute Sb in the Sb-Te octahedron, this turns into a Ag-Te defective tetrahedron with a strong Ag-Te bond that induces distortion in the crystal lattice. The formation of this bond is attributed to the electron configuration of Ag and its fully filled d orbital. Thus, Ag-doped Sb₂Te₃ is a promising candidate for practical phase change memory devices with high stability and high operation speed.