Effect of Layer Sequence on Formation of CdTe Thin Film Prepared by Stacked Elemental Layers

Three different sequences of Cd and Te were stacked to prepare polycrystalline CdTe thin films by the effect of annealing. X-ray diffraction analysis was used to characterize the prepared films. Although under some preparation conditions annealed films exhibit traces of Tellurium oxides, films of single polycrystalline CdTe phase have been successfully obtained even with annealing in air as an easy and simple manner. The best condition was sequence of glass/Te/Cd/Te and annealing at 200o C for 30 minutes. The grain size was determined by line profile analysis using WinFit computer program and Fourier analysis. It was proved that film with grains in the nanoscale region can be fabricated using this technique. It was found that the average crystallite size ≈ 9.4 nm and the cumulative size distribution showed that there are no grains larger than 30 nm. Transmission and reflection for thin film contain only CdTe were measured in the wavelength range 300-2500 nm. Optical energy gap was extracted from the manipulation of transmission and reflection data. The values of energy gaps (1.5-1.65 eV) verify that, the films under consideration are a polycrystalline CdTe films