Effect of Ar and H₂ mixture gas on SnS thin films deposited by radio frequency (RF) magnetron sputtering

The effect of hydrogen on the deposition of SnS films was investigated using conventional radio frequency (RF) magnetron sputtering. The structure of the deposited SnS films was transformed from amorphous to polycrystalline by increasing the partial pressure of H₂ gas. Simultaneously, the H₂ supply suppressed the formation of an extra S-rich phase and enabled the Sn/S composition to be controlled by exploiting the reaction between hydrogen and sulfur atoms. By increasing the H₂ supply, the Sn/S atomic ratio changed from 0.85 (S-rich) to 1.25 (Sn-rich). As the composition changes as a result of hydrogen supplementation, the carrier concentration of the SnS films decreases with increasing H₂ gas supply, which may be due to the increase in the enthalpy of formation of tin vacancies. The incorporation of hydrogen in the films was observed using secondary ion mass spectrometry measurements. The amount of incorporated hydrogen did not strongly depend on the amount of H₂ supplied. This suggests that hydrogen may not act as a carrier, but simply serves to modify the Sn/S ratio of SnS films using RF magnetron sputtering.