Co-evaporated SnS thin films for visible light photodetector applications
SnS thin films with different thicknesses have been deposited on glass substrates at a substrate temperature of 300 °C. The influence of thickness on structural, morphological, optical and electrical properties of the thin film has been investigated. X-ray diffraction (XRD) analysis and micro-Raman studies confirm the formation of single phase SnS films. Variation of surface morphology, roughness and average grain size of the as-deposited films have been examined by scanning electron microscopy (SEM) and atomic force microscopy (AFM). The optical properties such as film thickness (d), absorption coefficient (α), optical band gap (Eg), refractive index (n) and extinction coefficient (k) of the deposited thin films are estimated from the optical transmittance measurements. The optical energy band gap decreases from 1.51 eV to 1.24 eV with increase of film thickness. The electrical conductivity and photo-conductivity of the films increase by more than two orders with increase of film thickness from 170 nm to 915 nm. The visible photoresponsivity and specific detectivity of the films also increase with increase of film thickness. Hall effect measurements confirm the p-type nature of the as-prepared SnS thin films.