Thermal crystallization of amorphous Si/SiO2 superlattices

Annealing of amorphous Si/SiO2 superlattices produces Si nanocrystals. The crystallization has been studied by transmission electron microscopy and x- ray analysis. For a Si layer thinner than 7 nm, nearly perfect nanocrystals are found. For thicker layers, growth faults and dislocations exist. Decre asing the a-Si layer thickness increases the inhomogeneous strain by one or der of magnitude. The origin of the strain in the crystallized structure is discussed. The crystallization temperature increases rapidly with decreasi ng a-Si layer thickness. An empirical model that takes into account the Si layer thickness, the Si/SiO2 interface range, and a material specific const ant has been developed. (C) 1999 American Institute of Physics. [S0003-6951 (99)02618-2].