High sensitive samarium-doped ZnS thin films for photo-detector applications

Abstract We developed the ZnS and samarium-doped ZnS thin films for photo-detector applications via a simple Nebulizer Spray Pyrolysis technique. The structural, morphological, optical, and photo-detecting behavior of ZnS and Sm-doped (0.5, 1.0, and 1.5%) ZnS thin films were characterized by XRD, Raman, AFM, UV–Vis, and Keithley analyzer measurements. The XRD analysis confirms the hexagonal wurtzite structure with the polycrystalline nature of all the samples. This wurtzite nature of ZnS:Sm was also confirmed by E1 (LO) phonon mode present at 346 cm−1 in the Raman spectrum. AFM images and thickness measurement depicted enrichment of particles on the surface. The presence of constituents in the samples was identified by EDX analysis. The semiconducting nature of the prepared films was exhibited by optical studies and it shows the lowest optical band gap (Eg) value for the 0.5% Sm-doped ZnS (3.35 eV) thin film. Photo-sensing measurements was carried out by Keithley analyzer and showed the enhancement of sensing parameters up to 0.5% of Sm doping and then decreases for higher concentrated ZnS:Sm. The highest value of Responsivity (R), EQE, and Detectivity (D*) was 8.30x10−2AW−1, 28.26%, and 2.42 × 1010 Jones, respectively for as-prepared 0.5% Sm-doped ZnS. Hence, it clearly depicts that the doping of a small amount of samarium highly alters the host lattice and their photoconducting mechanism.