CdS Thin Films Deposited by a Modified Chemical Bath Deposition Method
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Abstract
Cds thin films were deposited on glass slide substrates by a modified chemical bath deposition technique using CdSO4 as the cadmium source. SC (NH2)2 as the sulfur source and NH3 as the complexing agent in deionized water bath. The modification to the traditional technique consists in applying the rotated substrate holder with controlled speed instead of using magnetic stirrer or a bath stirred by an impeller. As-deposited films were thermally annealed in a controlled N2 atmosphere. The annealing temperature was varied from 100-500 °C. Scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS) and X-ray diffraction (XRD) techniques were used to determine the morphology, compositions and crystalline structure of the films. The gradual structural transition from zincblende for the as-deposited CdS to wurtzite structure for the film annealed at 400 °C, the critical point of the phase transformation, was observed by XRD and optical transmission studies. Electrical sheet resistance of CdS thin films as a function of annealing temperature were also investigated. The appearance of the minimum sheet resistance of samples annealed at 200 – 300 °C, being around 4.6 x 104 Ω/square, was obtained in the darkness and under illumination conditions by using an ELH halogen lamp.
Keywords: Cds thin films, chemical bath deposition, optical transmission
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