Wettability inversion induced by weak electron irradiation

We investigate a wettability modification of ultrathin dielectric films induced by an electron irradiation. The effect of wettability inversion, transition from hydrophobic to hydrophilic state, is predicted for low irradiation doses. It is supposed that the inversion is caused by a change in the basic mechanism of the influence of an electron irradiation on the interface free energy. For high irradiation doses, the effect of the decrease in wettability under electron irradiation is caused by the interactions of an excess charge in the film with its image charges. At low doses, the mechanism is referred to the interaction of surface charges, which function as hydrophilic adsorption centers, with water molecules. The predicted effect of the wettability inversion has been experimentally verified with electron irradiation of silicon dioxide ultrathin films. A dramatic reduction in water drop surface tension on the liquid/vapor interface has been observed. Such reduction is explained by drop charging as a result of carriers tunneling from semiconductor through ultrathin oxide layer