The effect of composition on structural and optical properties of ZnSe alloys

Bulk of ZnxSe100−x (x=10, 20 and 40 at%) was prepared by the usual quench melt technique. Thin films of these compositions were prepared by thermal evaporation. Differential thermal analyses (DTA) on powder samples under non-isothermal conditions show that the glass transition temperature Tg increased and crystallization temperature Tp decreased with increasing Zn content. The average particle size of the crystalline ZnSe phase deduced from X-ray diffraction (XRD) patterns show a decrease with increasing Zn content. These results were confirmed with the results obtained by scanning electron microscopy (SEM). The optical properties of ZnxSe100−x have been studied at a wavelength range (300–900 nm), and it was found that the optical band gap (Eg) increases with increasing Zn concentration in the ZnxSe100−x system. The results can be interpreted on the basis of the chemical bond approach proposed by Bicermo and Ovshinsky. The value of the extinction coefficient (k) decreases with increasing wavelength and Zn content. On the other hand, the optical energy gap (Eg) decreased with increasing the annealing temperature for Zn10Se90 thin films. These results can be interpreted by the Davis and Motte model.