Optical properties of silicon nanocrystal superlattices

The many interesting and unique physical properties of nanocrystalline-Si/amorphous-SiO2 superlattices stem from their vertical periodicity and nearly defect-free, atomically flat, and chemically abrupt nanocrystalline-Si/SiO2 interfaces. By combining a less than 5% variation in the initial as-grown amorphous-Si layer thickness with control over the Si nanocrystal shape and crystallographic orientation produced via an appropriate annealing process, systems of nearly identical Si nanocrystals having remarkably different shapes (spheres, ovoids, bricks, etc.) have been produced. Such details governing the fabrication of nanocrystalline-Si/amorphous-SiO2 superlattices have dramatic effects on their structural and optical-Raman scattering and photoluminescence-properties. The reliable fabrication of Si-based nanostructures with control over the nanocrystal size, shape, and crystallographic orientation is an important first step in their applications in Si photonics.