Fundamental gap of luminescent nanocrystalline silicon thin film

Electroreflectance (ER) measurements have been made on luminescent nanocrystalline Si (nc-Si) films which were prepared with a plasma chemical vapor deposition method followed by anodization in HF aqueous solution. The ER features are observed between 1.2 and 1.4, at 2.2 eV and between 3.1 and 3.4 eV from the anodized nc-Si with mean crystal size ranging from <2 to ∼3 nm, and the ER features between 1.2 and 1.4 eV corresponding to the optical transitions at the fundamental gaps of the nc-Si films are affected by a decrease in the mean crystal size. By contrast, the ER spectrum of the as-deposited (not anodized) nc-Si film differs from that of the anodized film. From the chemical shift found in the Si 2p core level spectra, we conclude that the anodization-induced change in the ER spectra is mainly due to oxidation of the nc-Si films.