An IETS study of surface reactions applicable to adhesion

Inelastic electron tunneling spectroscopy (IETS) has been used to study two classes of adhesion promoting compounds adsorbed on alumina: trialkoxysilanes and phosphonic acids. It has been shown that both types of compounds can condense directly with hydroxyl groups on the surface. Condensation is through the alkoxy groups in the case of the silanes and through the hydroxyl groups in the case of the acids. The silanes can further condense to form surface siloxanes. The absence of bands characteristic of the phosphoryl group in the spectra of the acids is indicative of resonance bond formation followed by ionic bonding to the surface.