Optical and electrical properties of thin films of MnS/metal/MnS for photocatalysis and gas sensing applications

Abstract

Thin films of manganese sulfide (MnS) with interlayers of silver and copper were prepared using the thermal evaporation technique for applications in photocatalysis and gas sensing. The structure, morphology, optical, and electrical properties of the deposited films were described by X-ray diffraction (XRD), field emission scanning electron microscope (FE-SEM), UV/VIS/NIR spectrophotometer, and two-probe technique. Various parameters such as crystallite size, micro-deformation, dislocation density, optical energy gap, refractive index, extinction coefficient, Urbach energy, dielectric constants, dispersion parameters, activation energy, mobility and, Seebeck coefficient were determined. According to the experimental results, XRD analysis revealed that the MnS powder has a crystalline structure with a cubic phase. While the pure MnS thin films exhibited an amorphous structure, the addition of metals (Ag and Cu) as interlayers resulted in a distinct crystallinity. The pure MnS films had a direct optical energy gap of 3.17 eV, which changed to an indirect transition with energy gaps of 2.43 eV and 2.50 eV when Ag and Cu interlayers were added, respectively. The refractive index values and dispersion of the films depended on the type of interlayer, with all films exhibiting normal dispersion. The temperature dependence of the sheet resistance indicates a semiconducting behavior of the samples, and the addition of the interlayer metal reduced the sheet resistance. Overall, the results suggest that thin films of MnS and MnS/metal/MnS hold promise for organic photocatalysis and gas sensor applications, respectively.