Laser-induced hydrophobicity on single crystal zinc oxide surface

Highly hydrophobic surface of ZnO crystal substrate is prepared easily and rapidly by KrF excimer laser irradiation. The water contact angle is increased from 70 degrees to approximately 120 degrees. Through the XRD, AFM, XPS measurements and the Cassie-Baxter model analysis, it is indicated that the unique micro-nano fluctuant surface structure induced by laser irradiation is the prominent factor to the great increase of the water CA. The annealing treatments for the irradiated sample are carried out both in oxygen and vacuum atmosphere. It is found that the adsorption of oxygen atoms on the roughened surface could make the CA decrease abruptly at the first beginning, and after being stored at ambient atmosphere, the CA would reconvert to the value of the freshly irradiated sample gradually. It probably provides a convenient method for rapid conversion of the wettability through excimer laser irradiation and post annealing treatment. (C) 2012 Elsevier B. V. All rights reserved.