Mechanism of argon treatment on a growing surface in layer-by-layer deposition of hydrogenated amorphous silicon

Hydrogenated amorphous silicon (a-Si:H) samples were deposited by plasma-enhanced chemical vapor deposition at 50 MHz, using the layer-by-layer (LBL) technique. Thin sub-layer deposition at a high deposition rate of ∼0.9 nm/s (γ′ – or dust regime) was alternated by an Ar-treatment period. The density of deposited a-Si:H can be improved by Ar treatment. Some Ar is incorporated into the material and the band gap varies between 1.66 and 1.84 eV, by changing the Ar-treatment time from 0 to 50 s. This article demonstrates that changes in the band gap in a LBL process have no correlation with the total hydrogen content.