Effect of thiourea concentration on the growth and properties of Cu$_{3}$SnS$_{4}$ thin films prepared by spray pyrolysis

Abstract

$\hbox {Cu}_{3}\hbox {SnS}_{4}$ thin films were deposited onto soda-lime glass substrates held at $360\,^{\circ }$C using spray pyrolysis technique. The influence of thiourea concentration on the growth and properties of these films is studied by varying the thiourea concentration (0.04–0.09 M) and keeping cupric chloride (0.015 M) and stannic chloride (0.005 M) concentrations as constant in solution. These films were analyzed by studying their elemental composition, structural, microstructural, optical and electrical properties using appropriate characterization techniques. X-ray diffraction and Raman spectroscopy analyses revealed that the films deposited from solutions with 0.04 and 0.05 M thiourea concentrations contain CuS and $\hbox {Cu}_{2}\hbox {SnS}_{3}$ (CTS) phases, respectively. Nanocrystalline $\hbox {Cu}_{3}\hbox {SnS}_{4}$ films with cubic structure could be obtained by increasing the thiourea concentration from 0.07 to 0.09 M in the starting solution. The lattice parameter and crystallite size of these films are found to be 0.540 and 6 nm, respectively. The direct optical band gap of these films is found to decrease from 1.75 to 1.70 eV with increasing the thiourea concentration from 0.07 to 0.09 M in the solution. The room temperature electrical resistivity of these films is found to lie in the range $1.9\times 10^{-3}$–$0.9\times 10^{-3}\Omega$ cm.