Infrared vibrational spectra of rf-sputtered hydrogenated amorphous silicon

We report the vibrational absorption spectra between 200 and 4000 cm^-1 of a series of amorphous sputtered Si_1-xHₓ alloys prepared under different conditions of substrate temperature, and hydrogen, oxygen, and argon partial pressures. The spectra show stretching and wagging vibrational modes of the Si-H bond, and bending modes attributable to Si-H₂ configurations. Multiple features in the stretching vibrational spectrum are interpreted in terms of two different configurations of a single H atom. The integrated stretching vibrational absorption is correlated with the H content estimated from experiments on gas evolution upon heating. Finally, it is shown that different preparation conditions can lead to the same total H content but different vibrational spectra.