Free energy molecular dynamics simulations of pulsed-laser-irradiated SiO2: Si-Si bond formation in a matrix of SiO2

Recent experiments have shown that pure Si structures in a matrix of SiO2 can be formed by electron excitation techniques, with appealing applications in nanotechnology. Our ab initio simulations provide an insight into the underlying mechanism, showing that electron excitations weaken Si-O bonds in SiO2, dislodge O atoms and allow Si dangling bonds to reconstruct in stable Si-Si structures below the melting temperature. Differences in diffusivity of O (fast) and Si (slow) are shown to play a decisive role in the process.