A close investigation into the microstructure of SiO₂-doped Ge₂Sb₂Te₅ as a phase-changing material for nonvolatile memory application

Ge₂Sb₂Te₅ (GST) is widely employed as a functional material for phase-change random-access memory and SiO₂ doping has been reported to have a favorable effect on its characteristics for memory operations. This study is devoted to the formation mechanism of layered structures in SiO₂-doped GST (SGST)-a phasechange material with a high thermal efficiency due to its reduced thermal conductivity-with a particular focus on the microstructure of SGST thin films. Transmission electron microscopy and X-ray diffraction results demonstrate that LSs in SGST stem from an anisotropic driving force. Stress measurements performed during cyclic annealing clearly verify that the increase in tensile stress due to the presence of SiO₂ gives rise to an anisotropic driving force in the direction parallel to the substrate. Increased stress by SiO₂ doping is therefore shown to be essential to the formation of a layered microstructure.