Growth of thin Ti films on Al(110) surfaces

Abstract

High-energy ion scattering, x-ray photoemission spectroscopy, and low-energy electron diffraction (LEED) were used to study the interfacial reaction of very thin Ti films on Al(110) surfaces. The Al surface peak areas in the backscattering spectra of 0.96 MeV He+ ions incident along the [1̄1̄0] direction decreased sharply during the deposition of the first four monolayers of Ti. This suggests a growth model in which an ordered Ti overlayer shadows the Al surface atoms. This model is supported by electron diffraction measurements where sharp diffraction spots persisted with the rectangular symmetry of the substrate. Throughout this coverage regime, photopeak intensities due to Al were attenuated strongly with Ti coverage. With additional Ti deposition the Al surface peak intensities increase while the Al photopeak intensities remain unchanged, indicating a reaction at the Ti/Al interface that exposes additional Al surface atoms to the incident ion beam. Ion scattering spectra taken with the He+ ion beam incident along a random direction with respect to the Al substrate exhibit increased Ti peak areas indicating Ti shadowing. A LEED pattern was observed throughout the experiment suggesting the formation of an ordered overlayer. We present a growth model to explain these observations.