Characterization of Copper Sulphide (CuS) Thin Films Synthesized By Electroless Plating,

In this study, metallic copper (Cu) thin film was grown on soda lime glass substrate by electroless plating method and the as-grown Cu thin films were sulfurized using direct solvothermal sulfurization and thereafter annealed at 100 ⁰C, 200 ⁰C, 300 ⁰C, and 400 ⁰C. The film thickness, elemental composition, morphology, optical and electrical properties were investigated by using stylus surface Profilometer, energy dispersive x-ray spectroscopy, scanning electron microscopy, ultraviolet-visible spectroscopy and Four-Point Probe technique respectively. The EDS spectra analysis of CuS thin films confirms the presence of copper (Cu) and sulfur (S) along oxygen as an impurity which was attributed to open air annealing. At low annealing temperature, the material showed a compact smooth surface morphology but as the temperature increased the compact smooth surface of CuS agglomerated to form a dense and rough surface then a tiny popcorn-like structure started to grow. The increase in the annealing temperature demonstrate an improvement in the crystallinity of the material.  The material strongly transmit at the visible region of electromagnetic spectrum but has a poor transmittance at both UV and NIR region except the film annealed to 400 ⁰C, which decreased towards the NIR region but later increased slowly and constantly towards far infrared (FIR) region. This indicated that the films are capable of fairly suppressing UV and IR radiations while transmitting the visible radiations which could be suitable for solar control coatings. Film annealed at 400 ⁰C suppressed transmittance of UV radiation while fairly transmitting the VIS and IR radiations. The energy bandgap values were found to be 2.53 eV, 2.52 eV, 2.48 eV and 2.32 eV for annealing temperature at 100 ⁰C, 200 ⁰C, 300 ⁰C and 400 ⁰C respectively. As a result, the material can find application in many optoelectronic areas where low energy bandgap are desirable. The measured resistivity and evaluated conductivity were found to vary with annealing temperature. The resistivity decreased from 395.26 Ω m to 248.13 Ω m as annealing temperature increases from 100 ⁰C to 400 ⁰C for the CuS thin films. Therefore, the findings of the study shows that the variations in the annealing temperature alter the properties of the deposited copper sulphide thin films.

Keywords: Copper Sulphide (CuS), electroless plating