On nanometer ordering in thin amorphous hydrogenated silicon

Abstract

We investigated thin films of amorphous hydrogenated silicon (a-Si:H) deposited by PECVD under increasing dilutions of silane plasma by hydrogen. We found out that under increasing additional hydrogen at the depositions, thin films obtain less hydrogen bonded to silicon. The optical band gap energies determined from UV Vis transmittance and reflectance spectra were found to be increasing function of the dilution. We deduce that optical band gaps expanse due to the decreasing dimensions of silicon nanocrystals. They were calculated to be of 2 – 4 nm which proves the medium-range order in a-Si:H.