The adhesion behavior ofTi thin films to several oxide substrates has been studied. Ti was electron beam deposited onto single-crystal sapphire, magnesia, quartz, and fused silica substrates. Adhesion was measured by the peel test. Ti adhesion to sapphire was the highest, followed by magnesia, quartz, and fused silica, respectively. In situ x-ray photoelectron spectroscopy (XPS) studies demonstrate that the chemical effect is not a major factor in the adhesion strength in the systems investigated. The poor adhesion of Ti to fused silica and Ti reaction with fused silica detected by XPS suggest that the chemical reaction in the interface is not a sufficient condition for strong adhesion. It has been found that the mechanical effect of the substrate is more important in determining the peel strength. © 1987, American Vacuum Society. All rights reserved.