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 temp erature annealing. For ultrathin Si layers (similar to1-3 mn thick) crystal lization was not possible even after extensive annealing at temperatures up to 1100 degreesC, because of the high strain fields introduced by the SiO2 layers. However, for thicker layers (similar to4-20 nm thick) a variety of Si nanocrystals ranging in shape from spheres to bricks could be spontaneo usly formed and, in suitable cases, oriented along the < 111 > crystallogra phic direction. This formation of organized nanocrystals is an important st ep towards the construction of Si/SiO2 quantum devices. (C) 2001 Elsevier S cience B.V. All rights reserved.