Order-disorder phase change in embedded Si nano-particles

TL;DR

This study explores the temperature-dependent phase stability of embedded Si nanoparticles, revealing size-dependent order-disorder transitions and core-shell structures that differ from bulk silicon behavior.

Contribution

It demonstrates the size-dependent phase transition behavior of Si nanoparticles and details their internal structure, highlighting differences from bulk silicon.

Findings

Small nanoparticles are amorphous at low T and crystallize at high T.

Large nanoparticles are crystalline at low T and amorphous at high T.

Crystalline nanoparticles have an ordered core with a disordered shell.

Abstract

We investigated the relative stability of the amorphous vs crystalline nanoparticles of size ranging between 0.8 and 1.8 nm. We found that, at variance from bulk systems, at low T small nanoparticles are amorphous and they undergo to an amorphous-to-crystalline phase transition at high T. On the contrary, large nanoparticles recover the bulk-like behavior: crystalline at low T and amorphous at high T. We also investigated the structure of crystalline nanoparticles, providing evidence that they are formed by an ordered core surrounded by a disordered periphery. Furthermore, we also provide evidence that the details of the structure of the crystalline core depend on the size of the nanoparticle