Role of surface OH groups in surface chemical properties of metal oxide films

We investigated the effects of surface OH groups on surface chemical properties, such as wetting and surface reactivity of various metal oxide films. Linear relationship was observed between hydrophobicity caused by adsorption of organic substances from the atmosphere and surface OH group density. It was also found that surface reactivity with a fluoroalkyl isocyanate silane was strongly dependent upon the surface OH group density of the film. These results indicate that surface OH groups are a major factor governing the surface chemical properties of the films. It was also revealed that the surface OH group density depended on the film materials. This dependence can be explained in terms of electronegativity of the metal element directly bound to oxygen atoms. Utilizing these findings, the surface chemical properties of SiO2 films were successfully controlled.