Structural and optical properties of ZnxCd1-xSe thin films

Thin ZnxCd1-xSe films with a thickness ranging from 100 to 300 nm are prepared by thermal evaporation under a vacuum of 4.0 x 10(-4) Pa. Films deposited at substrate temperatures ranging from 570 to 625 K were found to be of polycrystalline nature, with sphalerite structure for x greater than or equal to 0.6 and wurtzite structure for x < 0.6. The optical constants n and k of ZnxCd1-xSe thin films of different composition were determined in the spectral range 400-2000 nm. The analysis of the accuracy of the adopted technique gave <plus/minus> 1.0% and +/- 0.5% for the real part of the refractive index n and the extinction coefficient k, respectively. The band gap showed a non-linear variation with the value of x and obeyed the empirical relation E-g(x) = 1.66 + 0.65x + 0.25x(2). The effective masses of the carriers and the band-gap bowing parameters of ZnxCd1-xSe thin films were estimated. (C) 2001 Elsevier Science B.V. All rights reserved.