Reversible crystalline–amorphous phase transitions in silicon under electron-beam irradiation: A unified beam-heating perspective

This preprint presents an updated, comprehensive study on reversible crystalline–amorphous phase transitions in silicon under electron-beam irradiation. Prior studies have independently reported electron-beam-induced crystallization of amorphous silicon (a-Si) and amorphization of crystalline silicon (c-Si), yet a unified explanation for these opposing transitions remains elusive. Conventional models invoke knock-on atomic displacement or bond breaking via electronic excitation, though it is counterintuitive that both could arise from the same athermal mechanisms. Using in situ transmission electron microscopy, we present the first direct observation of reversible transitions—from a-Si to c-Si and back—under constant irradiation. These findings challenge prevailing assumptions, suggesting distinct driving forces. To assess the possible contribution of beam heating to the driving forces, we employed a combination of Monte Carlo simulations and finite element analysis, incorporating Auger excitation as a plausible heating mechanism. The results reveal that heat accumulation becomes increasingly pronounced as thermal conductivity decreases from c-Si to a-Si. This trend suggests that crystallization in a-Si is driven by beam-induced heating, whereas amorphization in c-Si is primarily governed by knock-on atomic displacements. This study establishes a coherent framework for understanding electron–matter interactions and enables phase control in amorphous materials at the nanoscale.