STUDYING THE EFFECT OF DOPING BY SILVER ON THE OPTICAL PROPERTIES OF ZNIN2S4 THIN FILM

Abstract

In this research the optical properties of ternary ZnIn2S4 compound thin film of thickness (0.17 0.05)μm , which deposited on glass slides by chemical spray pyrolysis at 360oC were studied, Also studied the effect of doping by Ag element on the optical properties of the prepared thin films . From the absorption and transmission spectrum of the prepared thin films in the range (300 – 1000) nm, the optical constants were calculated. The absorption coefficient (α) was found to be greater than( 104)cm-1 for all films , this means that the electronic transitions of allowed direct type and the absorption edge is (442.85)nm for thin film ZnIn2S4 but when this thin film was doped by Ag element with amount of (1, 2, 3, 4 and 5)wt% the absorption edge was shifted toward the greater wavelength and arrive to (506.12)nm at 5%wt(Ag) without change in the electronic transitions type. The value of optical energy gap (Eg) for thin film ZnIn2S4 was (2.80)eV decreased non linearly with increases Ag element and arrive (2.45)eV at 5%wt(Ag).The higher value of extinction coefficient (K) were shifted toward the larger wavelength when the thin film ZnIn2S4 was doped by Ag .Also the higher values of refractive index (n) were shifted toward the larger wavelength with increases in doping ratio. The behavior of real dielectric constant (€1)and imaginary dielectric constant (€2) is similar to refractive index, and higher values shifted toward greater wavelength with increases in doping ratio . The tail width of the local states in the energy gap were calculated which was increased by adding the silver to the deposited film.