Opto-electrical characterisation of As33Se67−xSnx thin films

• Published in: Journal of alloys and compounds 2017-02, Vol.695, p.1532-1538
• Main Authors: El-Bana, M.S., Fouad, S.S.
• Format: Article
• Language: English
• Subjects: Chalcogenides; Dielectric properties; Linear and nonlinear optics; Optical energy gap; Thin films
• ISSN: 0925-8388; 1873-4669
• DOI: 10.1016/j.jallcom.2016.10.295

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 As33 Se67 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 ε1 &ε2 were used in order to study the dielectric behavior and to obtain many optelectrical parameters such as high-frequency dielectric constant,ε∞, lattice dielectric constant, εL, plasma frequency, ωp, relaxation time, τ, optical mobility, μopt, and optical resistivity ρopt. All of ε1, ε2, ε∞, εL, ωp, and optical conductivity, σ, were increased with increasing Sn content, whereas τ, μopt, ρopt and optical electronegativity, ηopt 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, Eg, stems from the difference of the binding energies of various bonds. Additionally, the nonlinear optical susceptibility χ(3) and the nonlinear refractive index n2 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. We have systematically investigated the optical properties of As33Se67-xSnx thin films. The dispersion of the refractive index has been analyzed in terms of the single-oscillator Wemple and DiDomenico model. The value of dispersion energy, Ed, the single-oscillator energy, E0, have been estimated as a function of Sn incorporation. A red shift in the transmittance edge has been observed due Sn incorporation (cf, Fig. 1). The variation of band gap as a function of Sn addition has been determined both experimentally and theoretically. The opto-electrical characterisations of studied compositions have been discussed in terms of the following parameters (real and imaginary parts of dielectric constants ε1 &ε2, the lattice dielectric constant εL, high frequency dielectric constant, ε∞, plasma frequency, ωp, relaxation time, τ, optical mobility, μopt, optical resistivity ρopt, optical electronegativity, ηopt, and optical conductivity, σ). Both linear and non-linear optical parameters have been det