Reversible wettability control of ZnO thin films synthesized by hydrothermal process on different buffer layers

• ZnO films were prepared by hydrothermal process on both AZO and ITO buffer layers.
• The ZnO film on AZO showed an imperceptible light-induced wettability response.
• The ZnO film on AZO showed a reversible thermal-incuced wettability transition.
• Both light- and thermal-induced wettability transitions of the ZnO/ITO were achieved.
• This work may provide a basis for wettability control in ZnO-based applications.

The wetting behaviors of zinc oxide (ZnO) thin films, which were grown on aluminum-doped zinc oxide (AZO) and tin-doped indium oxide (ITO) buffer layers by hydrothermal process, are reported. The ZnO film grown on the AZO layer, which has a morphology containing micro- and nanoscaled features, shows a slight decrease in water contact angle (WCA) after UV illumination. The ZnO film grown on the ITO layer, which is composed of single-scale microrods, exhibits a transition between hydrophobicity and superhydrophilicity under UV exposure for 8 h and dark storage for 2 weeks. The wettabilities of the both films are enabled to convert reversibly by alternative heating at 400 °C and 100 °C. This work may be of huge importance from the viewpoint of self-cleaning and anti-fogging applications based on wettability control of ZnO films.

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