IJSRSET173484 | Received : 26 July 2017 | Accepted : 05 August July- 2017 | July-August-2017 [(3)5: 321-323] © 2017 IJSRSET | Volume 3 | Issue 5 | Print ISSN: 2395-1990 | Online ISSN : 2394-4099 Themed Section: Engineering and Technology 321 Preparation and Physical Characterization of CDS thin Films Deposited by Chemical Spray Pyrolysis Hadi Ahmed Hussin Physics Department, Education College, Al-Mustansiriyah University, Baghdad, Iraq ABSTRACT Optical absorbance spectra of CdS thin films were recorded from UV-Visible spectrophotometer in the range 380- 900 nm. The films were prepared by chemical spray pyrolysis by spraying an aqueous solution of cadmium chloride (CdCl 2 ) and thiourea [(NH 2 ) 2 CS] with de-ionized water. The absorbance, refractive index, absorption coefficient increased with the increasing of CdS film thickness, while the extinction coefficient decreased. The energy gap decreased from 2.4 eV for thickness 500 nm to 2.37 eV for thickness 700 nm. Keywords: CdS Thin Film, Chemical Spray Pyrolysis, Optical Properties, Energy Gap. I. INTRODUCTION Cadmium sulphide (CdS) is one of the most promising II-VI compound semi-conductor materials because of its wide range of applications in different kind of hetero junction solar cells such as cadmium telluride (CdTe), copper indium diselenide/sulphide (CIS) and copper indium gallium diselenide/sulphide (CIGS) solar cells [1, 2]. CdS is a direct band gap of 2.42 eV II – IV semiconductor compound at room temperature and it has been studied for many years for various optoelectronic applications. Some applications of CdS thin films including photo detectors, piezoelectric transducers, bolo meters, solar cells, etc. [3]. Many techniques have been reported for the deposition of CdS thin films. These include thermal evaporation [4], sputtering [5], chemical bath deposition [6], spray pyrolysis [7], metal organic chemical vapour deposition (MOCVD) [8], molecular beam epitaxial technique [9], electro deposition [10], photochemical deposition [11] etc. In this work, the optical properties are studied for CdS thin films prepared by chemical spray pyrolysis. II. METHODS AND MATERIAL Experimental Details The CdS thin films were prepared by spraying an aqueous solution of cadmium chloride (CdCl2) and thiourea [(NH2)2 CS] with de-ionized water to form the final spray solution, a few drops of HCl were added to make the solution clear. A total volume of 100 ml was used in each deposition. The spray pyrolysis was done by using a glass atomizer, which has an output nozzle of 1 mm. The glass substrates at a temperature of 350 °C with the optimized conditions that concern the following parameters: spray time was 10 sec, the stopping period 3 minutes to avoid excessive cooling of glass substrate. The carrier gas (filtered compressed air) was maintained at a pressure of 105 Pascal, distance between nozzle and substrate was about 30 cm, solution flow rate 8 ml/min. Thickness of the sample was measured using the gravimetric method and was found to be 300 ± 20 nm. The optical properties are calculated from recording the absorbance spectra via UV-Visible spectrophotometer in the wavelength range (380-900) nm. III. RESULTS AND DISCUSSION From UV-Visible spectrophotometer, we recording the absorbance spectra in the range of 380-900 nm and then calculating the optical properties of CdS thin films. The absorbance spectra relationship with the wavelength is