Analysis of Zinc Sulphide (ZnS) and Cadmium Sulphide (CdS) thin films deposited by improved solution growth method at 300K

Abstract

We successfully deposited good quality semi conducting thin films of zinc sulphide (ZnS) and cadmium sulphide (CdS) on glass slides at 300K and pH values of 8, 10 and 12 by improved solution growth method. Ethylenediamine-tetra acetate (EDTA), another complexing agent, with pH oppose that of bath constitutions was added to bath reagents to enhance control and stabilize the deposition pH at different values suitable for film growth. X-ray diffraction method was used to confirm the depositions. Electron micrographs of the films reveal uniform surface deposition. Absorbance (A) spectra data were measured by a single beam spectrophotometer at wavelength range 200nm to 900nm. Other optical and solid state properties were calculated using the data and compared with other deposited thin films. Average optical and solid state properties of ZnS thin films include absorbance ranging from 0.049 to 0.110, transmittance 0.776 to 0.893, refractive index 1.63 to 2.02, film thickness 0.035 to 0.056μm and band gap 2.30 to 2.62 +0.05eV. For CdS thin films, the absorbance ranges from 0.067 to 0.080, transmittance 0.832 to 0.857, refractive index 1.76 to 1.84, film thickness 0.002 to 0.017μm and band gap 1.62 to 2.25 +0.05eV. Films with refractive index lower than 1.9 could be used in antireflection coatings, eyeglass coating and solar thermal control coatings. Those with refractive index greater than 1.9, could be useful in construction of poultry production, anti dazzling coatings and thin films solar cells.

Journal of the Nigerian Association of Mathematical Physics Vol. 9 2005: pp. 529-540