An X-ray Photoelectron Spectroscopy Study of Ultraviolet Photoannealing-Induced Surface Transformations of Sol–Gel Derived Zinc Oxide-Based Films

— X-ray photoelectron spectroscopy has been used to study structural evolution of zinc oxide synthesized by a sol–gel process adapted to flexible electronics. We assessed the effect of ultraviolet irradiation time on the atomic percentages of different Zn, O, and C species. Increasing the UV treatment time from 90 to 150 min has been shown to considerably reduce zinc concentration in the surface layer, which is accompanied by an increase in the percentage of carbon, predominantly in the form of highly oriented pyrolytic graphite. Photoactivation processes ensure completion of surface structure formation and lead to enrichment of the ZnO surface in oxygen with a binding energy of 531.5 eV, resulting in a zinc-deficient solid solution.