Electrically Driven Reversible Phase Change in Layered In2Se3 Crystalline Film
- Electrically Driven Reversible Phase Change in Layered In2Se3 Crystalline Film
- 정병기; 이수연; Min Sup Choi; Chang Ho Ra; Jee-Hwan Bae; Sungwoo Lee; Gun-Do Lee; Cheol-Woong Yang; James Hone; Won Jong Yoo
- Reversible Phase Changes; Phase-Change Memory; indium selenides; layered materials; metal-to-insulator transition; phase
changes; vacancy layers
- Issue Date
- Advanced materials
- VOL 2017-1703568-8
- An unconventional phase-change memory (PCM) made of In2Se3, which utilizes reversible phase changes between a low-resistance crystalline β phase and a high-resistance crystalline γ phase is reported for the first time. Using a PCM with a layered crystalline film exfoliated from In2Se3 crystals on a graphene bottom electrode, it is shown that SET/RESET programmed states form via the formation/annihilation of periodic van der Waals’ (vdW) gaps (i.e., virtual vacancy layers) in the stack of atomic layers and the concurrent reconfiguration of In and Se atoms across the layers. From density functional theory calculations, β and γ phases, characterized by octahedral bonding with vdW gaps and tetrahedral bonding without vdW gaps, respectively, are shown to have energy bandgap value of 0.78 and 1.86 eV, consistent with a metal-toinsulator transition accompanying the β-to-γ phase change. The monolithic In2Se3 layered film reported here provides a novel means to achieving a PCM based on melting-free, low-entropy phase changes in contrast with the GeTe– Sb2Te3 superlattice film adopted in interfacial phase-change memory.
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