Effect of annealing temperature on SnS thin films for photodetector applications

Tin sulfide (SnS) thin films were deposited at room temperature (RT) by thermal evaporation method and subsequently annealed at 150–350 °C in N2 atmosphere. The influence of annealing temperature on composition, structural, morphological and optical properties of the thin films has been investigated. X-ray diffraction (XRD) analysis and Raman studies confirmed the formation of single phase SnS films at RT and annealed up to 300 °C. The crystallite size increased from 24 nm for as-deposited film to 37 nm for the 300 °C annealed film and further reduced to 18 nm for the 350 °C annealed film. The film annealed at 200 °C was found to have better morphological features with (111) preferred oriented crystallites. The absorption coefficient, optical band gap (Eg) of the deposited films were estimated from the optical transmittance measurements. Photodetectors are fabricated by depositing Ag contacts on SnS thin films using a metal mask and photo response was tested under dark and illumination conditions using 532 nm laser of varying power intensities. The photodetectors performance is evaluated using responsivity (R), external quantum efficiency (EQE), and specific detectivity (D*). The specific detectivity of 6.8 × 1010 Jones obtained in the present study is nearly two orders of magnitude greater than that reported earlier.