Size-Controlled Si Nanocrystals Fabricated by Electron Beam Evaporation

Multilayers consisting of silicon nanocrystals (Si NCs) and SiO2 are successfully fabricated by electron beam evaporation, using pure Si and SiO2 targets in an oxygen-rich atmosphere for alternately depositing silicon-rich oxide (SRO) layers and SiO2 barriers, respectively. A post-deposition annealing process is carried out at different temperatures in order to achieve the Si precipitation in the form of nanocrystals. The stoichiometry of the layers is determined by X-ray photoelectron spectroscopy, which confirms the controlled silicon oxidation in order to attain SRO layers. Transmission electron microscopy and Raman-scattering measurements confirm the presence of crystalline Si-nanoprecipitates. Photoluminescence spectra from the Si NC samples can be deconvolved into two contributions, whose dynamics suggest that two different luminescent centers are responsible for the optical emission of the samples.