Dispersion Parameters and Energies of CdTe Nanostructure Thin Films for Optical Devices Applications

Document Type : Research Paper

Authors

1 Department of Physics, College of Education for Pure Sciences, University of Babylon, Hilla, Iraq

2 Department of Physics, College of Education for Pure Sciences, University of Babylon, Iraq

Abstract

There are numerous optoelectronic uses for semiconductor thin films II-VI. One such substance that has proven effective in creating solar cells, photodetectors, and other optical device applications is cadmium telluride (CdTe). In the current study, CdTe thin films were created by thermally vaporizing the material under a high vacuum and depositing them on glass substrates with different thicknesses. The effect of film thickness on structural, morphological, and optical properties was investigated. The thermal evaporated CdTe films were found to be polycrystalline with a cubic structure from the XRD test. Considerable improvement in the crystallinity was observed with the increase in thickness. The morphology of the film is examined by X-ray diffraction (XRD) and an atomic force microscope (AFM) confirming that the films grown had a good homogeneous surface. The roughness, root mean square value, and average diameter increased with the increasing thickness. The absorbance increased with the increasing thickness, while the transmittance decreased. The direct energy gap decreased from 3.35 to 3.1 eV with increased thickness. The dispersion parameters of the films were also evaluated using Wemple– DiDomenico (WDD) single oscillator model. The dispersion energy (Ed) and oscillator energy (Εo) of the films were evaluated and varied in the range of 4.9–2.1 eV and 5.09 –6.09 eV respectively. Moreover, the optical dispersion moments (M-1 and M-3) were also calculated that varied from 0.4 to 0.8 and from 0.017 to 0.022 respectively.

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