半导体中自放大局域动力学不稳定性引起的光致非热熔化的晶种和均匀形核
The seeds and homogeneous nucleation of photoinduced nonthermal melting in semiconductors due to self-amplified local dynamic instability
摘要：
激光诱导半导体非热熔化在过去的四十年里一直在研究，但其基本机制仍在争论中。在这里，通过利用先进的实时时间相关的密度泛函理论模拟，我们发现，光激发诱导的超快非热熔化硅发生通过均匀成核与随机种子起源于自放大的局部动态不稳定性的光激发态，而不是同时打破所有的债券，如建议的惯性模型，声子不稳定性，或库仑排斥机制。由于这种局部动力学不稳定性，原子的任何初始小的随机热位移可以通过光激发载流子的电荷转移来放大，这反过来又为激发载流子产生局部自陷中心并产生随机成核种子。这一发现为光诱导超快非热熔融提供了新的见解。
英文摘要：
Laser-induced nonthermal melting in semiconductors has been studied over the last four decades, but the underlying mechanism is still under debate. Here, by utilizing an advanced real-time time-dependent density functional theory simulation, we reveal that the photoexcitation-induced ultrafast nonthermal melting in silicon occurs via homogeneous nucleation with random seeds originating from a self-amplified local dynamic instability at the photoexcited states rather than by simultaneously breaking of all bonds, as suggested by the inertial model, phonon instability, or Coulombic repulsion mechanisms. Due to this local dynamic instability, any initial small random thermal displacements of atoms can be amplified by a charge transfer of photoexcited carriers, which in turn creates a local self-trapping center for the excited carriers and yields the random nucleation seeds. This finding provides fresh insights into photoinduced ultrafast nonthermal melting.
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