CdS Thin Films Deposited by a Modified Chemical Bath Deposition Method

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

Corresponding author: E-mail:  kwngamni@kmitl.ac.th