Tuning Optical Character of ZnO Thin Films with Ag Doping by Different Synthetic Routes

Silver (Ag) doped zinc oxide (ZnO) thin films are synthesized through three different methods namely sol–gel deposition, electrodeposition, and chemical bath deposition (CBD) on conducting glass substrate. The XRD patterns of ZnO and Ag/ZnO visibly revealed the presence of hexagonal wurtzite polycrystalline structure with the films oriented along the (101) plane. The shift in peak position with silver doping provided a strong evidence of Ag+ substitution for the Zn2+ site. The crystal structure, surface morphology and the particle size distribution were monitored for the 0.5 to 4 wt % Ag content. The SEM analysis evidently showed the effect of Ag+ doping whereby a highly porous structure was obtained for the CBD films and a layered structure for the sol–gel and electrodeposition films. The UV–Vis transmittance and absorbance spectra showed highest transmittance in sol–gel films which further increased on Ag+ addition and a decrease in transmittance was observed in electrodeposited and CBD films. The higher absorbance and longer absorption window (up to 900 nm) were recorded in CBD and electrodeposition films than to that of sol–gel films. Lowering in band gap of the CBD films (up to 1.98 eV), a slight decrease in electrodeposited films (3.12 eV) and nearly no change in the sol–gel films (3.20 eV) was recoded upon silver doping.