Mitrofanov Kirill V, Fons Paul, Makino Kotaro, Terashima Ryo, Shimada Toru, Kolobov Alexander V, Tominaga Junji, Bragaglia Valeria, Giussani Alessandro, Calarco Raffaella, Riechert Henning, Sato Takahiro, Katayama Tetsuo, Ogawa Kanade, Togashi Tadashi, Yabashi Makina, Wall Simon, Brewe Dale, Hase Muneaki
Nanoelectronics Research Institute, National Institute of Advanced Industrial Science &Technology (AIST), Tsukuba Central 5, Higashi 1-1-1,Tsukuba 305-8562, Japan.
RIKEN SPring-8 Center, 1-1-1 Kouto, Sayo-cho, Hyogo 679-5148, Japan.
Sci Rep. 2016 Feb 12;6:20633. doi: 10.1038/srep20633.
Phase-change materials based on Ge-Sb-Te alloys are widely used in industrial applications such as nonvolatile memories, but reaction pathways for crystalline-to-amorphous phase-change on picosecond timescales remain unknown. Femtosecond laser excitation and an ultrashort x-ray probe is used to show the temporal separation of electronic and thermal effects in a long-lived (>100 ps) transient metastable state of Ge2Sb2Te5 with muted interatomic interaction induced by a weakening of resonant bonding. Due to a specific electronic state, the lattice undergoes a reversible nondestructive modification over a nanoscale region, remaining cold for 4 ps. An independent time-resolved x-ray absorption fine structure experiment confirms the existence of an intermediate state with disordered bonds. This newly unveiled effect allows the utilization of non-thermal ultra-fast pathways enabling artificial manipulation of the switching process, ultimately leading to a redefined speed limit, and improved energy efficiency and reliability of phase-change memory technologies.
基于锗锑碲合金的相变材料广泛应用于非易失性存储器等工业领域，但皮秒时间尺度上从晶体到非晶态相变的反应路径仍不清楚。利用飞秒激光激发和超短X射线探针，展示了在Ge2Sb2Te5的长寿命（>100 ps）瞬态亚稳态中电子和热效应的时间分离，这种亚稳态通过共振键减弱诱导原子间相互作用减弱。由于特定的电子态，晶格在纳米尺度区域经历可逆的非破坏性修饰，保持4 ps的低温状态。一项独立的时间分辨X射线吸收精细结构实验证实了存在键无序的中间态。这种新揭示的效应允许利用非热超快路径，实现对开关过程的人工操控，最终导致重新定义速度极限，并提高相变存储技术的能量效率和可靠性。
