Structural and optical properties of flash evaporated AgInTe₂ thin films

Ain Shams University, Faculty of Education, Physics Department, Thin Film Laboratory, 11757/352, Cairo, Egypt

Corresponding author: amaelbarry@yahoo.com

Received: 30 November 2005
Revised: 16 December 2005
Accepted: 20 January 2006
Published online: 12 July 2006

Abstract

Thin films of AgInTe₂ were prepared on quartz substrates by a flash evaporation technique at substrate temperature ~303 K. The compositions of both the bulk and thin films, with thickness (~208–350 nm), were checked using energy dispersive X-ray spectroscopy (EDX). X-ray diffraction (XRD) measurements showed that AgInTe₂ compound is characterized by a tetragonal structure while the as deposited films have amorphous nature. On annealing at 423 and 573 K (for two hours and under vacuum ~10⁻³ Pa), the films were identified to be single-phase, polycrystalline with a preferred (112) orientation. The optical properties of the films were investigated using spectrophotometric measurements of transmittance and reflectance at normal incidence in the wavelength range (~500–2500 nm). The refractive index (n) and the absorption index (k) of AgInTe₂ were determined from the absolute values of the measured transmittance and reflectance. It was found that both (n) and (k) depend markedly on the temperature of heat treatment. The dispersion of refractive index in AgInTe₂ was analyzed using the concept of the single oscillator model. Within this concept some dispersion parameters were determined for as deposited and annealed flash evaporated AgInTe₂ films at 423 K for 2 h. The calculated values of β indicated that AgInTe₂ films belong to ionic class. The ratio of the free carrier concentration to the effective mass (N/m*) were, also determined. The analysis of the absorption coefficient indicated that, this ternary chalcopyrite compound has three allowed direct transitions corresponding to three energies gaps Eg₁, Eg₂ and Eg₃. The crystal field (Δ_cf), the spin orbit (Δ_so) and the deformation potential (b) were calculated for both as deposited and annealed flash InAgTe₂ films at ~423 K for 2 h.