Optimisation of spin coating parameters for the preparation of ZnO thin films by Grey-Taguchi method

This work studies the influence of spin coating process parameters on grain size and surface roughness of zinc oxide (ZnO) thin films by sol gel using Taguchi method. ZnO thin films were prepared using zinc acetate dehydrate (ZAD), methanol and diethanolamine (DEA) as the starting material, solvent and stabilising agent respectively. The coating parameters such as precursor concentration of ZAD (0.5, 0.6 and 0.7 M), spin speed (1,500, 2,500 and 3,500 rpm) and annealing temperature (300,400 and 500 °c) was selected and the influence of these parameters on grain size and surface roughness was studied using X-ray diffraction (XRD) and atomic force microscopy (AFM). ANOVA results showed that annealing temperature had 53% effect on grain size and chuck rotation speed had 40% effect on the surface roughness of the film. Using Grey relation technique the optimised parameters was found to be 0.5 M, 2,500 rpm and 400°C. The grain size decreased from 18.054 nm to 16.97 nm and roughness of film decreased from 230.47 nm to 223.5 nm.