Surface wettability and optical properties of ZnO nanostructured films

• Main Authors: Po-Wei Chi, 紀柏葦
• Other Authors: Da-Hua Wei
• Format: Others
• Language: en_US
• Published: 2017
• Online Access: http://ndltd.ncl.edu.tw/handle/58e7qx

博士 === 國立臺北科技大學 === 機電學院機電科技博士班 === 105 === This work has focused on the study of structure, morphology, chemical adsorption, surface wettability, and optical properties of hydrophobic ZnO nanostructured films onto glass substrate by using magnetron sputtering technique. We systematically modulated grain structure from nano- to micro- types by controlling the various internal stress states of films to study the relationship between morphology and surface wettability. The evolution of surface wettability was found to change from hydrophobicity to hydrophilicity as transforming the internal stress states from compressive to nearly-free, meanwhile, the ability of surface chemical absorption is getting weak. Moreover, glancing angle deposition (GLAD) method was used to improve the surface wettability of ZnO nanostructured films. While the ZnO film sputtered at the glancing angle of 30◦, the numbers of smaller grains spread onto the film surface and stacked, then, begins to form many smaller size apertures that could provide much more opportunity for air storage and become air pocket to shore up the water droplet that leads to better surface wetting behavior. However, the surface morphology transition can be attributed to the shadow effect which is induced during GLAD process. In addition, we first found that the surface wettability and optical properties of ZnO nanostructured films can be improved and controlled by capping with various thicknesses of magnetic metal layer, besides, to the best of our knowledge, the thickness effect of magnetic metal capping layer atop textured ZnO related to the unique physical properties is seldom studied. Firstly, pure ZnO nanostructured film exhibits a remarkable near-band-edge emission peak located at around 370 nm with a bandgap of 3.35 eV. When a single magnetic metal layer ranged from 5 to 20 nm was capped onto ZnO film, the intensity of near-band-edge emission peak decreased and the emission band shifted. This phenomenon was due to the oxygen vacancy effect and could be attributed to rise concentration of structural defects in the bilayer films. Therefore, a simple tunable method is achieved and presented here that the surface wettability and optical property of ZnO phase can be effectively controlled by capping a single bimetallic magnetic layer. The magnetic metal/ZnO heterostructure bilayer films exhibited many novel and valuable magnetoelectric applications in future due to its multifunctional behaviors.