Absorption and dispersion studies of thermally evaporated nanocrytallite structure ZnIn₂Se₄ thin films

Department of Physics, Faculty of science at Damietta, New Damietta 34517, Egypt

Corresponding author: hzeyada@gmail.com

Received: 4 May 2008
Revised: 5 December 2008
Accepted: 12 December 2008
Published online: 6 February 2009

Abstract

ZnIn₂Se₄ has a polycrystalline structure in as synthesized condition. It transforms to nanostructure grains of ZnIn₂Se₄ upon thermal deposition as thin films. The optical properties of as deposited ZnIn₂Se₄ films are studied using spectrophotometer measurements of transmittance and reflectance at normal incidence of light in wavelength range (450–2500) nm. The refractive index and absorption index are calculated and it is found that they are independent of film thickness in the thickness range (500–790) nm. Absorption analysis showed two types of electronic transitions; indirect allowed transition with energy gap 1.76 eV accompanied by phonon of energy 25 meV and direct allowed transition with energy gap 2.3 eV. The dispersion analysis showed that the oscillator energy, dispersion energy, dielectric constant at infinite frequency and lattice dielectric constant are 2.49 eV, 14.36 eV, 6.84 and 8.17, respectively.