Optical spectroscopic analysis of annealed Cd_1−xZn_xSe thin films deposited by close space sublimation technique

Cd_1−xZn_xSe (x = 0, 0.40 and 1) thin films were deposited on a glass substrate at room temperature by closed space sublimation method. Optical investigation has been performed using spectrophotometry and ellipsometry. It has been found that for as deposited films the optical band gap increased and the optical constants decreased with increasing Zn content. To improve the optical properties of Cd_1−xZn_xSe thin films annealing effect at 400 °C was taken into consideration for various Zn contents. It was observed that the optical transmittance and band gap decreased while optical constants increased with increasing Zn content after annealing. The effects of composition and annealing on the optical dispersion parameters E_o and E_d were investigated using a single effective oscillator model. The calculated value of the average excitation energy E_o obeys the empirical relation (E_o = E_g/2) obtained from the single oscillator model.