Realization of multi-level phase-change in Sb7Se3/Ge50Te50 bilayer films via decoupling interlayer coupling between Sb7Se3 and Ge50Te50 layers

Multi-level phase-change can not only increase the storage density of phase-change memory, but also has important applications in neuromorphic computing. However, its realization is still very challenging. Here, we study the phase-change behaviors of four bilayer films, Sb7Se3(x nm)/Ge50Te50(90 nm), with x = 30, 50, 70, and 100. The expected three-level phase change is not observed at all. Raman and XRD characterizations reveal the occurrence of interlayer coupling between Sb7Se3 and Ge50Te50 layers. De-coupling structure films, Sb7Se3(x nm)/Si(50 nm)/Ge50Te50(90 nm), are proposed and prepared, where the amorphous Si layer serves as de-coupling the interlayer coupling. Three-level phase change is observed in all de-coupling Sb7Se3(x nm)/Si(50 nm)/Ge50Te50(90 nm) films. Our works demonstrate the effect of interlayer coupling on multi-level phase-change, and the de-coupling idea provides a design way for multi-level phase-change materials.