The Study of Annealing  and Dopping Effect of Zn  on Structural and Optical Properties for CdTe Thin Films

	The Study of Annealing and Dopping Effect of Zn on Structural and Optical Properties for CdTe Thin Films
Ibn Al-Haitham Journal For Pure And Applied Science
Article 1, Volume 25, Issue 1, 2012, Pages 127-134
Abstract
In this research thin films of (CdTe) have been prepared as pure and doped by Zn with different ratios (1,2,3,4,5)% at thickness (400+25)nm with deposition rate (2±0.1)nm , deposited on glass substrate at R.T. by using thermal evaporation in vacuum . All samples were annealed at temperature (523,573,623,673)K at 1h. The structural properties of all prepared thin films, doped and undoped have been studied by using XRD. The analysis reveals that the structures of the films were polycrystalline and typed cubic with a preferred orientation along (111) plane for the undoped films with (2,3)% of zinc , and shifting (2Ɵ) for doped films . The annealing films at temperature 573 K and Zn:3% show decreasing in intensity at orientation along (111) with appearing new peaks for ZnTe & Te. Transmittance spectra recorded a function of wavelength (400-1100) nm for all films in order to calculate (know) the energy gap, kind of transitions and optical constants like absorption coefficient, refractive index as a function of photon energy. It is found that the energy gap for the allowed direct transition decreases as the doping percentage increase, such that its value for allowed direct transition was (1.62) eV for pure thin films , it decreased to (1.585) eV when it doped with 4% . It is found that the annealing process increases the energy gap.

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