Thermal crystallization of amorphous Si/SiO2 superlattices

Abstract

Annealing of amorphous ${\mathrm{Si/SiO}}_{\mathrm{2}}$ 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. Decreasing the $\mathrm{a-}\mathrm{Si}$ layer thickness increases the inhomogeneous strain by one order of magnitude. The origin of the strain in the crystallized structure is discussed. The crystallization temperature increases rapidly with decreasing $\mathrm{a-}\mathrm{Si}$ layer thickness. An empirical model that takes into account the Si layer thickness, the ${\mathrm{Si/SiO}}_{\mathrm{2}}$ interface range, and a material specific constant has been developed.