Abstract

Ion-assisted deposition (IAD), the bombardment of thermally evaporated thin films by low-energy ions during growth, has been used very successfully to density thermally evaporated coatings.¹ However, the physical mechanism involved in this densification Is still unclear. The only theoretical attempt to explain this densification is that of Müller.^2,3 He first investigated the effect on film densification of thermal spikes,² ion-induced localized annealing events for which the relevant ion parameter is the ion energy. The conclusion was that these annealing events do not significantly density the films under typical IAD conditions. A collisional cascade model³ then showed that film densification can be caused by the recoil implantation of near-surface atoms, a momentum dependent process. We therefore decided to perform an experiment that would differentiate between energy and momentum effects in the IAD process.

© 1988 Optical Society of America