Fabrication and characterization of silicon nanocrystals by thermal oxidation of a-Si:H films in air

Hydrogenated amorphous silicon (a-Si:H) and Si–O–H heterogeneous thin films have been examined for their potential to photoluminesce. In this study, 50 nm a-Si:H films were deposited and oxidized to understand how film morphology affects their optical properties. Glancing angle x-ray diffraction (XRD), x-ray reflectivity, x-ray photoelectron spectroscopy, optical absorption spectroscopy in the wavelength range 250–1000 nm, and Fourier transform infrared measurements were used to complement room temperature photoluminescence (PL) studies. The results are discussed in light of the standard models for room temperature visible PL for a-SiOx:H films and silicon nanocrystals. The PL peak at 1.6 eV arises from silicon nanocrystals. Modeling this band to estimate the quantum dot size indicates that the mean silicon crystallite diameter is ∼5 nm, while XRD analysis gives ∼9±1 nm. The discrepancy in the estimation of crystallite size by the XRD method and PL analysis is attributed to the columnar growth of the sili...