Abstract
Nanocrystalline silicon (ns-Si) thin films deposited through plasma-enhanced chemical vapor deposition technique were studied. These films were grown at low deposition temperature of 200 degrees C and at different silane flow rates ([SiH4]). Characterization of these films with Raman spectroscopy, x-ray diffraction and atomic force microscopy revealed that no films deposited at [SiH4] = 0.0 sccm. In addition, the structural change from an amorphous to a nanocrystalline phase at [SiH4] = 0.2 sccm. The Fourier transform infrared spectroscopic analysis showed at low values of [SiH4] (0.1 sccm), no hydrogen incorporated in the nc-Si thin film. However, the intensity of the spectra around 2100 cm (1) is likely to decreases with increasing [SiH4]. We have observed photoluminescence (PL) at room temperature in the range of 1.7 eV to 2.4 eV for all the films. Presence of the very small crystallites (the size less than 20 nm) responsible for quantum confinement effect. Variations of the PL intensity, width and position are well correlation with the structural properties of the films such as crystalline size, crystalline volume fraction, and hydrogen content. Furthermore, the PL emissions also showed correlation with the distribution of spherical grains with the size below 50 nm distributed on the films surface.