Simple views on metal/oxide interfaces: Contributions of the long-range interactions to the adhesion energy

The image and van der Waals contributions to the metal/oxide work of adhesion are compared through the extent to which they follow the known prevalent trends, i.e. the increase in work of adhesion (a) with narrowing oxide band gap and (b) with increasing conduction electron density of the metal. The van der Waals interaction is shown to follow both trends, while the image term is suggested to be significant only for dense metals in contact with very ionic oxides. The relative contribution of these long-range interactions to the overall metal/oxide work of adhesion is found to bi, maximized for systems involving metals with low electronic densities and oxides with wide band gaps. At variance, high metallic electronic densities and narrow oxide gaps likely favour short-range interactions arising from charge transfer.