Water-Resistant and Antibacterial Zinc Aluminate Films: Application of Antibacterial Thin Film Capacitors

Because of the widespread use of smartphones, the smartphone panel glass can be easily infected by various bacteria and needs to be coated with hydrophobic materials to avoid fingerprints on the screen. Accordingly, an environmentally friendly smartphone panel glass that is resistant to variations in transmittance due to contact with water and acidic water is required. In this study, we demonstrate that our smartphone glass comprising a 30 nm-thick ZnAl2O4 film has high transparency and strong antibacterial activity, is resistant against water and acidic water, and has hydrophobicity without a protective layer with hydrophobic properties. After being dipped in deionized water or acidic water for 10 days, the panel glass-coated ZnAl2O4 films revealed similar transmittances to that of glass, as well as exhibiting strong antibacterial activity against Escherichia coli and Staphylococcus aureus without dissolution of Zn2+ and Al+3 ions and variations in the surface morphology. Moreover, the hydrophilicity of the as-deposited films could be spontaneously changed to hydrophobicity to avoid fingerprints on the screen via a simple heat treatment. The strong antibacterial thin film capacitors were demonstrated using dielectric ZnAl2O4 films and top/bottom electrodes of Al-doped ZnO (AZO)/Ag/AZO multilayer films.