Effect of Reaction Temperature on Structural Growth, Optical, and Electrical Properties of Cu-doped ZnS Thin Film Synthesized via Spray Pyrolysis Technique

Abstract

Cu-doped ZnS (CuZnS) thin films were deposited via chemical spray pyrolysis, and the effect of substrate temperature on their structural, optical, and electrical properties was investigated. XRD and Raman analysis were conducted to study the structural properties of the grown CuZnS thin films and the analysis revealed a moderate polycrystalline structure with mixed phase of hexagonal and less cubic phases. The strain of about 3.29 × 10−2 and the density of dislocation of about 8.436 × 1016 lines/m2 were found at 410 °C. Double bandgaps of about 3.4 eV and 3.1 eV were obtained from Tauc’s plots of the utilized substrate temperatures. From the modified Scherrer equation, crystallite sizes of about 4.427 nm and 3.443 nm at the substrate temperatures of 380 °C and 410 °C respectively were obtained.  The structural analysis and the obtained Urbach energy showed the presence of imperfections and residue stresses in the grown CuZnS thin films which revealed the unattained thermodynamic stability in the phase transitioning to a dominant hexagonal phase in grown CuZnS even at 410 °C. The analysis results indicated that CuZnS thin films grown via spray pyrolysis for optoelectronic applications including UV photodetectors and LEDs, are best deposited at a substrate temperature above 410 °C and under sufficiently controlled surrounding environment within the enclosure of the machine to avoid unnecessary oxidation at elevated temperatures