Influence of argon dilution on growth and properties of hydrogenated nanocrystalline silicon films

The effect of argon concentration (66–87%) in total gaseous mixture (SiH4+H2+Ar) on growth and properties of hydrogenated nanocrystalline silicon films deposited by RF (13.56 MHz) PECVD technique was investigated. Raman and XRD measurements revealed increasing argon fraction favored enhancement of crystallinity, enlargement of crystallites and relaxation of strained bonds. Photoluminescence spectra of nc-Si:H films exhibited two radiative transitions in the photon energy ranges of 2.8–3.1 eV and 1.6–2.1 eV. The high energy PL peaks are attributed to surface effect of the films whereas peaks in the range of 1.6–2.1 eV are due to nanocrystallinity in the films. Argon dilution also helped enhancement of deposition rate and conductivity of the films. A film deposited at 81% of argon fraction possesses high crystallinity (75%), conductivity in the order of 10−5 (Ω cm)−1, size of the crystallite (Raman=12 nm, XRD=18 nm), and low residual stress (125 MPa).