Effect of substrate pretreatment by ion sputtering on adhesion has been studied for the case of thin Ti films deposited on two different oxide substrates, namely, fused silica and sapphire. Peel test measurements showed that the peel strength of Ti on the oxide substrates was enhanced as the ion sputter time was increased at a constant ion flux. In situ x-ray photoelectron spectroscopy was used to investigate the chemical interaction of Ti with the sputtered substrate. Intermediate oxidation state of titanium, i.e., a TiOx-like (1 <x< 1.5) state, was formed at the interaction sites on both treated and untreated substrate surfaces. Comparison of the x-ray induced O(KVV) Auger spectra evolved at different Ti coverages on these substrates suggested that ion sputtering created additional interaction sites on the substrate surface. Surface extended electron energy-loss fine structure above the oxygen K edge was used to investigate the local structure of the ion sputtered substrates. The bond length determined by this technique for the sputtered surface is consistent with the scenario that ion sputtering creates defects in the top monolayers of the substrate, which provide the increased interaction sites. © 1988, American Vacuum Society. All rights reserved.