| AVS 62nd International Symposium & Exhibition | |
| Electronic Materials and Processing | Tuesday Sessions |
| Session EM-TuP |
| Session: | Electronic Materials and Processing Poster Session |
| Presenter: | Masayuki Takato, Graduate School of Engineering, Nagoya University, Japan |
| Authors: | M. Takato, Graduate School of Engineering, Nagoya University, Japan H. Shirakawa, Graduate School of Engineering, Nagoya University, Japan M. Araidai, Graduate School of Engineering, Nagoya University, Japan K. Shiraishi, Graduate School of Engineering, Nagoya University, Japan |
| Correspondent: | Click to Email |
Superlattice phase change memory (superlattice PCM) consisting of (GeTe)2/Sb2Te3 stacked structure is one of the most promising candidates for next-generation non-volatile memories and has received considerable attention in recent years [1,2]. The memory operations are attributed to small structural change between two atomic configurations before and after switching. Therefore, the energy required for switching between higher and lower resistive states is much lower than that of conventional PCMs utilizing phase transition between crystal and amorphous phases [3]. However, the reaction pathway in switching of superlattice PCM has not yet been clarified and the detailed analyses of the structural transition between high-resistive and low-resistive states are prerequisites for fully understanding the switching mechanism.
In this work, we investigated the switching process of the superlattice (GeTe)2/Sb2Te3 PCM using the first-principles electronic states calculations. The atomic structures and the electronic states were calculated by VASP code [4], which is based on density functional theory with the plane-wave basis sets, a PBE-type exchange-correlation functional and the projector augmented-wave method. For the calculations, k points of 8 x 8 x 4 Monkhorst-Pack grid were used and the cutoff energy was 500eV.
We found that atomic configurations of high-resistive and low-resistive states are not stable but metastable [5]. Therefore, the superlattice (GeTe)2/Sb2Te3 PCM can do cyclic operations due to the metastability. In addition, we clarified the structural transition process between high-resistive and low-resistive states. I will show the detail process in the announcement. Furthermore, the validity of our proposal will be shown from the detailed analyses of the potential energy surface and electron-density distribution.
[1] J. Tominaga, et al., Jpn. J. Appl. Phys. 48, 03A053 (2009).
[2] N. Takaura, et al., IEDM Tech. Dig., p.685 (2014).
[3] R. E. Simpson, et al., Nat. Nanotech. 6, 501 (2011).
[4] G. Kresse and J. Hafner, Phys. Rev. B 47, 558 (1993).
[5] R. Ohyanagi, et al., Appl. Phys. Lett. 104, 252106 (2014).