title: Photoinduced hydrophilicity of heteroepitaxially grown ZnO thin films.
abstract: Single crystalline ZnO thin films were heteroepitaxially grown on sapphire substrates by rf-magnetron sputtering. The ZnO films on sapphire A and C face were oriented along the (0001) direction, whereas the ZnO film on sapphire R face was oriented along the (11-20) direction. The rate of photoinduced hydrophilic conversion strongly depended on the surface crystal structure. The ZnO film oriented along the (11-20) direction exhibited a higher hydrophilicizing rate than those oriented along the (0001) direction. The high hydrophilicizing rate of the ZnO oriented along the (11-20) direction is due to its surface atomic arrangement. The outermost layer of the ZnO surface of the (11-20) face contains oxygen ions, which are considered to be energetically reactive sites and responsible for the hydrophilic conversion.
authors.affiliation: Research Institute, TOTO Ltd., 2-8-1 Honson, Chigasaki-shi, Kanagawa, 253-8577, Japan. masahiro.miyauchi@toto.co.jp
authors.forename: M
authors.initials: M
authors.lastname: Miyauchi
authors.forename: A
authors.initials: A
authors.lastname: Shimai
authors.forename: Y
authors.initials: Y
authors.lastname: Tsuru