Opto-electrical characterisation of As33Se67-xSnx thin films

We have systematically investigated the optoelectrical properties of As33Se67-xSnx (x = 0, 2, 4 and 6) thin films. The optical parameters have been determined using transmission spectra in the spectral range (400 nm-2000 nm). Addition of Sn to As-33 Se-67 thin films was found to affect the refractive index, n, extinction coefficient, k, and all related parameters. The dispersion of the refractive index has been discussed in terms of the single-oscillator model. The real and imaginary parts of dielectric constants epsilon(1) & epsilon(2) were used in order to study the dielectric behavior and to obtain many optelectrical parameters such as high-frequency dielectric constant, epsilon(infinity), lattice dielectric constant, epsilon(L), plasma frequency, omega(p), relaxation time, tau, optical mobility, mu(opt), and optical resistivity rho(opt). All of epsilon(1), epsilon(2), epsilon(infinity), epsilon(L), omega(p), and optical conductivity, sigma, were increased with increasing Sn content, whereas tau, mu(opt), rho(opt) and optical electronegativity, eta(opt) were decreased with increasing Sn percent in the studied films. A red shift in the transmittance edge has been observed due to Sn incorporation. The decrease of the estimated optical energy gap, E-g, stems from the difference of the binding energies of various bonds. Additionally, the nonlinear optical susceptibility chi((3)) and the nonlinear refractive index n(2) were estimated from linear optical parameters using semi-empirical relations. Moreover, the effect of Sn incorporation on the non-linear optical parameters has been also discussed. (C) 2016 Elsevier B.V. All rights reserved.