Atomistic modelling of the interface structure of Si nanocrystals in silica

Abstract

Silicon as the basis of the conventional microelectronics industry is expected to be able to integrate both optical and electronic functionalities, leading to optics on silicon chips. Nevertheless, the long radiative lifetimes have until now obstructed efficient light amplification in this material. A novel nano-crystalline approach has disclosed a new prospect for silicon in the laser application field. The observed superior light emitting properties (compared to regular and porous silicon) of silicon nanocrystals (Si-nc's) embedded into amorphous silica (a-SiO2) are associated with more stable Si/SiO2 interfaces in the new structures. However, the mechanism of this phenomenon still remains unclear, in part since the atomic structure of the Si-nanocrystal interface has not been known. In the present work, by means of molecular dynamics atomistic models, small Si-nc's embedded into defect-free a-SiO2 are constructed using two different classical interatomic potentials. After series of annealing runs, the interface structure and defects were carefully analyzed. The results show a thin suboxide layer, along with mostly undercoordinated defects at the interface region.