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[Display omitted] • Design strategy of phase change material properties are developed for low-energy memory application. • Low operation energy condition is explored automatically through Bayesian optimization. • Operation energy is lowered by decreasing thermal conductivity, ratio of volume resistance to contact resistance and phase change temperature. • According to the developed design strategy, operation energy of typical Ge-Sb-Te can be decreased to less than 1/100 in phase change memory application. Aiming at reducing energy consumptions in data writing, the development of new memory materials is highly required. To develop new phase change materials (PCMs) with extremely low operation energy used in non-volatile memory, such as storage-class memory, we performed Bayesian optimization for the physical properties of PCMs through numerical simulations. In this numerical simulation, the electrical potential and temperature distribution were solved simultaneously. It was found that a PCM with low thermal conductivity, low melting temperature, and low ratio of contact resistance to volumetric resistance results in a low operation energy of a PCM-based memory application. Finally, we developed a design strategy for PCMs. New PCMs should be developed by lowering the operation energy E , described as E = κ (1 + C)Δ T /Δ z , where κ is the thermal conductivity of the PCM, Δ T is the melting temperature, C is the ratio of contact resistance to the volumetric resistance, and Δ z is the thickness of the PCM. The present results clarify the relationship between thermal and electrical properties for lowering operation energy ever hidden in previous studies. According to the design strategy, an operation energy in phase change memory application can be decreased to less than 1/100 compared with conventional Ge-Sb-Te compounds. [ABSTRACT FROM AUTHOR]

[Display omitted] • GeSb/HfO 2 superlattice-like films were prepared by magnetron sputtering. • The thermal stability of GeSb/HfO 2 is greatly improved. • Under the influence of HfO 2 , the grain size of the film decreases to 3.34 nm. • The density of the film decreased to 4.27% before and after phase transition. • The energy required for RESET operation of Ge 1 Sb 9 /HfO 2 superlattice-like film is low. This paper focused the effect of the recombination of HfO 2 on the phase change behavior and crystalline properties of Ge 1 Sb 9 /HfO 2 superlattice-like phase change films. Compared with pure Ge 1 Sb 9 , the Ge 1 Sb 9 /HfO 2 superlattice-like film has higher crystallization temperature, better data retention ability and larger activation energy, indicating excellent thermal stability. With the increase of HfO 2 thickness ratio, the band gap becomes wider. Atomic force microscopy and X-ray diffraction tests illustrate that HfO 2 composite layers can inhibit the growth of grain, reduce the grain size and have a smoother surface. X-ray reflectivity tests show that Ge 1 Sb 9 /HfO 2 film has a small volume fluctuation during the crystallization process. Raman spectroscopy is used to observe the molecular vibration. Phase change memory devices based on Ge 1 Sb 9 /HfO 2 thin film are fabricated to evaluate its electrical performance. The results reveal that HfO 2 composite layers play a significant role in improving thermal stability, refining grain size and reducing power consumption on Ge 1 Sb 9 phase change film. [ABSTRACT FROM AUTHOR]