Influence of Cu doping on physical properties of sol-gel processed SnS thin films

Copper-doped tin sulfide thin films (Cu-SnS) with different Cu doping concentrations were prepared by using the spin coating technique and their structural, electrical, and optical properties were studied. All the prepared films were polycrystalline and exhibited diffraction peaks corresponding to orthorhombic SnS with the preferred (111) orientation. The XRD spectra revealed improvement in the preferential orientation and crystalline quality with up to 4% Cu doping concentration, whereas Cu doping concentrations above 4% deteriorate the preferential orientation and crystalline quality. It has been observed that upon Cu doping the band gap decreased significantly from 1.46 eV (pure SnS) to 1.37 eV (4% of Cu-doped SnS). Hall measurements revealed the p-type semiconducting nature of the SnS thin films. The observations revealed that doping of SnS with Cu causes a noticeable drop in the room-temperature resistivity value from 105 Ω-cm for pure SnS to 103 Ω-cm for 4% Cu-doped SnS.