First-principles molecular dynamics simulation reveals the effects of electronic excitation in the amorphization of Ge-Sb-Te. The excitation makes the phase change an element-selective process, lowers the critical amorphization temperature considerably, for example, to below 700 K at a 9% excitation, and reduces the atomic diffusion coefficient with respect to that of melt by at least 1 order of magnitude. Noticeably, the resulting structure has fewer wrong bonds and significantly increased phase-change reversibility. Our results point to a new direction in manipulating ultrafast phase-change processes with improved controllability.

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On the basis of ab initio molecular dynamics modeling, we show that Ge-Sb-Te alloy under excitation can realize amorphization without going through a liquid phase. The electronic structure analysis further reveals that the excitation mainly involves the Ge s-like states near the valence band maximum. After the phase transition, the coordination number of Ge is reduced from six to four, while the change in the coordination number for Sb is noticeably less.