The Effect of Non-Thermal Plasma on the Topographical and Optical Constants of Cd Doped ZnO Thin Films

Abstract

Nanostructured ZnO and Cd doped ZnO were deposited employing spray pyrolysis technique. Atomic force microscope and double beam spectrophotometer were utilized to study the influence of non-thermal plasma on topographical and some optical constants. AFM results indicate that the average diameter was 43.4-68.81 nm before exposure and their values was slightly influenced by exposure to plasma to be 42.74-69.25 nm and all the result indicate the deposited films have a nanostructure. Surface roughness R_a and root mean square roughness R_rms were in the ambit of (2.09-5.3 nm), (2.43-6.12 nm) before exposure to plasma, while their values were in the ambit of (2.09-5.3 nm),(2.58-10.3 nm) after the influence of plasma. Optical constants such as absorbance was increased with the increment of Cd content, the same trend was noticed after exposure to non thermal plasma. High absorbance was seen near 400 nm. Whereas extinction coefficient,refractive index show a decrement with the increment of Cd content before and after exposure to plasma. Reflectance also offers the same trend of the above optical constants, a comparatively low reflectance is shown for the pure ZnO thin films before and after exposure Finally, all the studied parameters were influenced by plasma exposure.