Investigation of samarium-doped PbS thin films fabricated using nebulizer spray technique for photosensing applications

Lead sulfide (PbS) and samarium-doped (1, 3, and 5 wt%) PbS thin film layers were coated facilely on glass slides using the nebulizer spray procedure. To investigate the doping effect on the crystal structure, morphology, light absorption, and emission features of the deposited films X-ray diffraction, Raman, Scanning electron microscope, UV-Visible absorption, and photoluminescence spectroscopic analyses were carried out. A Keithley source meter was used to study the electrical characteristics of the thin film coatings. All the prepared films reveal the fcc lattice structure of PbS. Additional diffraction peaks related to the Sm2O3 phase are observed when 5 wt % of Sm was added to PbS. From Raman analysis, the peaks observed at 192, 235, and 465 cm(-1) confirm the presence of the PbS phase. The scanning electron micrograph of the PbS thin film reveals that it has tightly packed grains of spherical shape. In the case of Sm-doped PbS films, the mean grain size increases with the Sm doping concentration. The energy dispersive X-ray analysis shows the existence of Pb, S, and Sm which authenticates the presence of the Sm element in the PbS matrix. The optical studies reveal that the 5 wt% Sm-doped PbS thin film has lower transmittance and higher absorption value. Moreover, the optical band gap value is decreased from 2.15 to 1.58 eV when Sm doping concentration increases from 0 to 5 wt%. The highest photocurrent is observed for the 3 wt% Sm-doped PbS thin film sample. The photocurrent enhancement due to the samarium doping with PbS makes it a potential candidate for the photosensor applications.