Structure and thermal stability of noncrystalline silicon nanoparticles during heating and melting

Abstract

The changes in the structure and kinetic properties of glassy and amorphous Si{300}, Si{400}, and Si{500} nanoparticles during heating from 300 to 1700 K are studied by molecular dynamics simulation. The nano-particle density increases with temperature and approaches the density of bulk solid silicon. As the temperature increases to 1400 K, a unimodal bond length distribution changes into a bimodal distribution, which is more pronounced for glassy nanoparticles. The average bond length in an amorphous nanoparticle is, as a rule, longer than in a glassy nanoparticle, and the average number of bonds per atom in it is smaller than in the glassy nanoparticle at almost all temperatures. The excess potential energy is negative in the central concentric layers of nanoparticles. In the vicinity of melting, liquid layers form in the near-surface region of nanoparticles. A kinetic criterion indicating the beginning of melting of nanoparticles is formulated.