Electrical and optical characterization of CdxZn1-xs thin films deposited by chemical bath deposition in alkaline conditions

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Date
2014-04Author
John, Okumu
Njoroge, Walter N.
Mosiori, Cliff Orori
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In this work ternary CdZnS thin films were prepared by chemical bath deposition by doping CdS with different
concentrations of Zn ions. The chemical bath comprised of cadmium nitrate [Cd(NO3)2], as a source of Cd2+, zinc
nitrate [ZnNO3)2]as source of Zn2+, thiourea [(NH2)2CS] as a source of sulphide ions [S2-]in the presence of ammonia
[NH3] as a complexing agent. The competition mechanisms of Cd2+ and Zn+2 with the complexing agent [NH3] to
form complex ions usually plays a critical role in the formation of CdxZn1-xS thin films and therefore the influence of
Zn2+ on the formation mechanisms of the CdxZn1-xS was discussed. Optical and electrical properties of these
samples were analysed. Parameters like band gap (Eg), extinction coefficient (k), absorption coefficient (α),
dielectric constant (ε), refractive index, (n)and resistivity (ρ) were calculated using the data obtained from different
measurements. Optical band gap tunability of the deposited films for various Zn2+ concentrations was successfully
demonstrated by UV-VIS-NIR spectroscopy. Transmittance inCdxZn1-xSwas found to be above 80%, optical band
gap of 2.47-2.72 eV, refractive index of 2.58 – 2.39, and sheet resistivity of 1.09– 1.36 × 102 -cm for x = 1.0 – 0.6.
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- RP-Department of Physics [100]