Abstract:
Synthesis of cobalt sulphide thin films (t ≈ 537 nm) in an aqueous alkaline medium (pH = 11) on the glass micro slides using liquid phase chemical deposition process is presented. Cobalt sulphate and thiourea were used as the precursors. The deposition temperature and time were 56 0 C and 80 minutes, respectively. The possible growth mechanism and reaction kinetics are suggested. Dark green coloured, tightly adhered, uniform, and diffusely reflecting deposits are obtained using this technique. An EDS analysis suggests that the deposits are Co-rich. The structural studies revealed hexagonal wurtzite structure of the CoS films with excellent match of the d-values and lattice parameters. The average crystallite size determined using FWHM method is in the nano range (≈ 15 nm). The absorption coefficient of the CoS thin film is high (α ≈ 10 4 – 10 5 cm-1 ) and a direct band gap of 1.13 eV has been observed. The room temperature dc electrical conductivity is 5.25 x 10-6 (Ω cm)-1 and activation energy of the intrinsic conduction is found to be 0.671 eV. The thermo probe measurements showed n-type conduction of the sample. Surface morphology shows a network of elongated thread like crystallites tapered at both ends, randomly oriented and threaded into each other.
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