R&D: Quasicrystalline Phase-Change Memory

Nature Scientific Reports has published an article written by Eun-Sung Lee, Joung E. Yoo, Du S. Yoon, Sung D. Kim, Material Research Center, SAIT, Samsung Electronics, Suwon, 16678, Republic of Korea,Yongjoo Kim, Department of Materials Science and Engineering, Yonsei University, Seoul, 03722, Republic of Korea,Soobin Hwang, Dasol Kim, Department of Physics, Yonsei University, Seoul, 03725, Republic of Korea, Hyeong-Chai Jeong, Department of Physics and Astronomy, Sejong University, Seoul, 05006, Republic of Korea, Won T. Kim, Department of Optical Engineering, Cheongju University, Cheongju, 28503, Republic of Korea, Hye J. Chang, Hoyoung Suh, Advanced Analysis Center, Korea Institute of Science and Technology, Seoul, 02792, Republic of Korea, Dae-Hong Ko, Choonghee Cho, Yongjoon Choi, Do H. Kim, Department of Materials Science and Engineering, Yonsei University, Seoul, 03722, Republic of Korea, and Mann-Ho Cho, Department of Physics, Yonsei University, Seoul, 03725, Republic of Korea.

Abstract: “Phase-change memory utilizing amorphous-to-crystalline phase-change processes for reset-to-set operation as a nonvolatile memory has been recently commercialized as a storage class memory. Unfortunately, designing new phase-change materials (PCMs) with low phase-change energy and sufficient thermal stability is difficult because phase-change energy and thermal stability decrease simultaneously as the amorphous phase destabilizes. This issue arising from the trade-off relationship between stability and energy consumption can be solved by reducing the entropic loss of phase-change energy as apparent in crystalline-to-crystalline phase-change process of a GeTe/Sb₂Te₃ superlattice structure. A paradigm shift in atomic crystallography has been recently produced using a quasi-crystal, which is a new type of atomic ordering symmetry without any linear translational symmetry. This paper introduces a novel class of PCMs based on a quasicrystalline-to-approximant crystalline phase-change process, whose phase-change energy and thermal stability are simultaneously enhanced compared to those of the GeTe/Sb₂Te₃ superlattice structure. This report includes a new concept that reduces entropic loss using a quasicrystalline state and takes the first step in the development of new PCMs with significantly low phase-change energy and considerably high thermal stability.“