Fast in Situ Ultrahigh-Voltage Electron Microscopy Observation of Crystal Nucleation and Growth in Amorphous Antimony Nanoparticles

Abstract

Electron-irradiation-induced crystallization processes and the mechanisms in amorphous antimony nanoparticles have been investigated by microsecond temporal and picometer spatial resolution in situ observations. Electron irradiation experiments and the simultaneous in situ observations were carried out with an ultrahigh-voltage electron microscope operating at an accelerating voltage of 1 MV, which has a temporal resolution of 625 μs per frame. At the early stage of the crystallization in approximately 20 nm amorphous nanoparticles, a small crystal nucleus on the surface repeats between formation and annihilation. When the nucleus size becomes more than the critical size of 6.3 nm in diameter, crystal growth takes place in the whole nanoparticle. The crystal growth rate estimated was approximately 20 μm s–1. The growth rate depends on the particle size, and it was confirmed that the smaller the particle size, the faster the growth rate. It was suggested that the crystallization driven by long-range elastic interaction due to small crystal nucleus formation in amorphous nanoparticles is induced by short-range atomic rearrangements.