lower thermal conductivity of superlattice thin films compared to that of bulk materials. [8][9][10] In recent years, superlattice structure PCM has drawn the most attention in the field since they reduce the energy consumption while can still maintain other good performances (such as density, speed, endurance, and signal contrast) and realize controllable multilevel storage to increase storage density. [11][12][13] From the viewpoint of thermodynamics, the smaller the cell size, the less the input energy can be, thus superlattice structure phase change materials were theoretically designed based on suppressing the ratio of a mixing entropy from the beginning and reducing the energy consumption. [14] The explanation for these improvements is still under debate, their atomic structure and switching mechanism need to be explored. [15] Materials with two or three metastable intermediate resistance levels are promising candidates for multi-level data storage devices. [16][17][18] A multilayer PCM thin film generally comprises two PCM constituents alternatively deposited, with one phase of high phase change speed and the other phase of good amorphous stability. Most PCM materials are compounds located in pseudo-binary line GeTe-Sb 2 Te 3 showing high distinguishable phases and cyclability, scalability. [19][20][21] However, a few studies showed that superlattice-like structures of GeTe-Sb 2 Te 3 exhibit the tendency to intermix during deposition. [22][23][24][25][26] Searching for new compositions with other elements should be a promising way to further optimize the superlattice-based PCM. The crystallization temperature of Sb 2 Te 3 is too low to be utilized in practical products. [27] Ge 2 Sb 2 Te 5 is the core composition in almost all PCMs owing to comprehensive properties, it was reported by Yamada et al. [28,29] GaSb layer has also been proposed for phase change materials since their unique crystallization process is effective in enhancing thermal stability. [30][31][32] Especially, Ga-Sb thin films exhibited an unusual behavior with a decreasing mass density upon crystallization compared to GeTe thin films, [33] which can compensate for an increased density of GST thin films. The recent studies [9,34] evidenced that the superlattice PCM provides an effective means to tune and balance the properties such as thermal stability and read/write speed of the device. On the other hand, the mechanical properties of superlattice thin films have been proved to show abnormal effects with super-hardness and super-modulus in certain ranges.