Transformation of cadmium hydroxide to cadmium oxide thin films synthesized by SILAR deposition process: Role of varying deposition cycles

Abstract

Successive Ionic Layer Adsorption and Reaction (SILAR) was used to deposit nanocrystalline cadmium oxide (CdO) thin films on microscopic glass substrates for various cycles (40–120). This is based on alternate dipping of the substrate in CdCl2 solution made alkaline (pH _12) with NaOH, rinsing with distilled water, followed by air treatment with air dryer and annealing at 300 _C for 1 h in air. The prepared films were characterized by X-ray diffraction (XRD), UV–Visible Spectrophotomer (UV–Vis) and Scanning Electron Microscopy (SEM). The 80th cycle was observed to be the saturation stage for this reaction. The XRD results confirmed the films to be CdO with some Cd(OH)2 phase at higher deposition cycles. The films were polycrystalline in nature having high orientation along (111) and (200) planes. As the number of cycles increases the calculated average crystallite sizes increase gradually up till the 80th cycle after which a gradual decrease in the crystallite size was observed with increasing number of cycles. The films’ transmittance in the visible and near infrared region decreased as the number of cycles increased and ranged between 25 and 80%. This work shows the feasibility of using simple SILAR method at room temperature to obtain Cd(OH)2 films which are transformed to CdO thin films after annealing.