**1. Introduction**

Cadmium oxide (CdO) thin films are one of the transparent conducting oxide (TCO) materials and have been fascinated the investigators for their remarkable properties such as tunable band structure, high extinction coefficient, possible multiple exciton generation, electronic and transport properties [1–4]. CdO is a degenerate n-type semiconductor with a wide energy gap and high electrical conductivity [5]. Its high electrical conductivity is due to the increased grain size at high substrate temperature, moderate electron mobility, and high carrier concentration. The properties of CdO can be controlled to a suitable value to for the suit particular applications by controlling some of the process parameters viz. film thickness, the temperature of the substrate, pH value of the solution, Wt.% and solution flow rate etc. Though CdO is a first transparent conducting oxide film studied by Bedekar in 1907, not many investigations have been done for quite a long time. During last few years CdO is being extensively investigated in bulk and

thin film form. CdO has interesting properties like large band gap, low electrical resistivity and high transmission in the visible region etc. These characteristics make it suitable for a variety of applications, including photodiodes, phototransistors, photovoltaic transparent electrodes, liquid crystal displays, IR detectors, and anti-reflection coatings [6–10].

For the last few decades various techniques such as chemical vapor deposition, sputtering, chemical bath deposition, sol–gel, SILAR, thermal evaporation, layer by layer assembly, spin coating, activated reactive evaporation, metal organic chemical vapor deposition (MOCVD), pulsed laser deposition and spray pyrolysis techniques are employed for the preparation of CdO thin film [11–29]. Among these routes, spray pyrolysis technique is a simple and low cost chemical method for the preparation of thin films with large area of coating. In this work the simplified perfume atomizer spray pyrolysis homemade setup is used for prepare a CdO thin films. The usage of a perfume atomizer offers a number of advantages over traditional spray gun assembly: low cost, no need for carrier gas, fine atomization, better wettability between sprayed micro particles, and nearly no loss of the precursor to the environment. We recently demonstrated that by effectively synthesizing CdO films, this simplified spray process can be a desirable alternative to the standard spray technique. The structure, morphology and optical behavior of the film depend on molarity, solution pH, substrate temperature, age of solution and solution volume. The precursor solution pH affects the hydrolysis and condensation behavior of the solution, which, in turn, influences the structure of the resultant film, morphological and optical behavior of the films. The role of the solution aging on the properties of thin films and interesting photo luminescent characteristics had been already reported [30–32]. In general, the properties of coated film depend on pH of the precursor solution, substrate temperature, molarity of the starting solution and solution volume. In this chapter, the effect of volume of solution on the structural, morphological and optical properties of CdO films prepared by perfume atomizer spray pyrolysis deposition method were investigated and reported in detail (Section 2).

### **2. Experimental**

CdO films have been prepared by using cadmium acetate dihydrate as a source material of Cd and double distilled water was used as solvent. The glass substrates of 1.5 cm × 1.5 cm were used for the CdO deposition. The substrates were cleaned following a well-established methodology consisting on an initial washing step with soap and water followed by a washing procedure using acetone and isopropyl alcohol in an ultrasonically bath and a final rinsing step with distilled water [33]. For the implementation of the perfume atomizer spray pyrolysis method, homemade system was designed and implemented (**Figure 1**).

The system consists on a perfume atomizer, a power supply and a heating plate. The optimized deposition parameters such as substrate – spray nozzle distance (25 cm), spray angle (about 45°), spray time (5 s) and spray interval (30 s) were kept constant. The precursor solution was prepared at room temperature and kept on a container attached to the atomizer. Once the precursor solution was prepared, cleaned glass substrates were positioned onto the heating plate and heated until the temperature of the substrates reached to the desired value. The glass substrates were positioned at a horizontal separation distance of 25 cm from the perfume atomizer. The CdO thin films have been prepared by spraying a solution (30, 40 and 50 mL) composed of cadmium acetate dissolved in double distilled water and when the droplets of sprayed solution reached the preheated substrate, owing to the *Structural, Morphological and Optical Properties of Perfume Atomizer Spray Pyrolysis CdO… DOI: http://dx.doi.org/10.5772/intechopen.99906*

**Figure 1.** *Perfume atomizer spray setup.*

pyrolytic decomposition of solution, a well adherent, pinhole free, uniform yellowish colored films of cadmium oxide are formed on the substrate surface according to the following reaction [34, 35].

$$\text{Cd(CH}\_3\text{COO)}\_2 + \text{3H}\_2\text{O} \rightarrow \text{CdO} \downarrow + \text{CH}\_4 \uparrow + 4\text{H}\_2 \uparrow + \text{3CO}\_2 \uparrow \tag{1}$$

After the CdO deposition on the glass substrate, the samples were cooled down at room temperature and stored in dry conditions for further characterization. For the present study, the appropriate chemical and physical parameters were changed to study the effect of solution volume such as 30, 40 and 50 mL on structural, morphological and optical properties of CdO thin film.
