Self-organization and ordering in nanocrystalline Si/SiO2 superlattices

The solid phase crystallization of nanometer-thick layers of disordered Si confined between layers of amorphous SiO2 has been achieved using high temperature annealing. For ultrathin Si layers (∼1–View the MathML source thick) crystallization was not possible even after extensive annealing at temperatures up to 1100°C, because of the high strain fields introduced by the SiO2 layers. However, for thicker layers (∼4–View the MathML source thick) a variety of Si nanocrystals ranging in shape from spheres to bricks could be spontaneously formed and, in suitable cases, oriented along the 〈111〉 crystallographic direction. This formation of organized nanocrystals is an important step towards the construction of Si/SiO2 quantum devices.