Thickness Dependence of Structural and Optical Properties of CdTe Films

Zarei Moghadam, R.; Ehsani, M.H.; Rezagholipour Dizaji, H.; Sazideh, M.R.

doi:10.22068/ijmse.15.3.21

Volume 15, Issue 3 (September 2018) IJMSE 2018, 15(3): 21-31 | Back to browse issues page

‎ 10.22068/ijmse.15.3.21

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Zarei Moghadam R, Ehsani M, Rezagholipour Dizaji H, Sazideh M. Thickness Dependence of Structural and Optical Properties of CdTe Films. IJMSE 2018; 15 (3) :21-31
URL: http://ijmse.iust.ac.ir/article-1-1101-en.html

Thickness Dependence of Structural and Optical Properties of CdTe Films

R. Zarei Moghadam

, M.H. Ehsani

, H. Rezagholipour Dizaji

, M.R. Sazideh

Abstract: (16822 Views)

In this work, Cadmium Telluride (CdTe) thin films were deposited on glass substrates at room temperature by vacuum evaporation technique. The deposited CdTe thin films were characterized by X-ray diffraction, UV-Visible spectroscopy and Field emission scanning electron microscope (FESEM) techniques. Structural studies revealed that the CdTe films deposited at various thicknesses are crystallized in cubic structure. The results showed the improvement of the film crystallinity upon grain size increment. Optical constants such as refractive index (n), extinction coefficient (k), real and imaginary parts of dielectric constant, volume energy loss function (VELF), and surface energy loss function (SELF) were calculated using UV-Vis spectra. In addition, band gap and Urbach energies were calculated by Tauc and ASF methods. The band gap energy of the specimens was found to decrease from 1.8 to 1.4eV with increasing the thickness of films. The absorption coefficient, computed and plotted versus the photon energy (hν) and tailing in the optical band gap, was observed which is understood based on Urbach law. Urbach energy variation from 0.125 to 0.620 eV in the samples with higher thicknesses is concluded.

Keywords: Cadmium Telluride (CdTe), thin films, evaporation technique, Urbach energy