Influence of Cd-content on structural and optical dispersion characteristics of nanocrystalline Zn1-xCdxS (0 ≤ x ≤ 0.9) films

Low cost dip coating technique was successfully used to deposit highly uniform and good adhesive nanocrystalline Zn1-xCdxS (0 <= x <= 0.9) thin films. The surface morphology and crystalline structural characteristics of Zn1-xCdxS were achieved by using atomic force microscopy (AFM) and transmission electron microscopy (TEM), respectively. Transmission spectra show red shifting of absorption edge as the Cd content increased. The optical constants were accurately determined by using reflectance and transmittance spectra. The effect of Cd-content on refractive index, extinction index and other optical dispersion parameters were also investigated. The dispersion of the refractive index was discussed in terms of single oscillator model. In addition, the ratio of free carrier concentration to its effective mass was estimated. The calculated value of oscillator energy E-o obeys the empirical relation (E-o approximate to 2 E-g), obtained from single oscillator model. Small magnitude of optical electronegativity (chi*) for Zn1-xCdxS (0 <= x <= 0.9) thin films and relatively high refractive index can be attributed to covalent nature, in agreement with beta value, obtained from dispersion energy analysis. Moreover, molar polarizability and third-order nonlinear optical susceptibility were also considered. (C) 2014 Elsevier B.V. All rights reserved.