Structural characterization of nc-Sia-SiO_2 superlattices subjected to thermal treatment

摘要

The morphology of nanocrystalline (nc)-Si/amorphous (a)-SiO_2 superlattices (SLs) is studied using Raman spectroscopy in the acoustic and optical phonon ranges, transmission electron microscopy (TEM), and atomic force microscopy (AFM). It is demonstrated that high temperature annealing (up to 1100deg C) and oxidation in O_2/H_2O ambient do not destroy the SL structure, which retains its original periodicity and nc-Si/a-SiO_2 interface abruptness. It is found that oxidation at high temperatures reduces the defect density in nc-Si/a-SiO_2 SLs and induces the lateral coalescence of Si nanocrystals (NCs). The size, shape, packing density, and crystallographic orientation of the Si nanocrystals are studied as a function of the oxidation time.