A direct comparison of the visible and ultraviolet reflectance of aluminum films evaporated in conventional and ultra-high vacuum systems

Abstract

Aluminum was evaporated in a conventional evaporator using an oil diffusion pump ( p=3 × 10 -6 torr) and in an ultra-high vacuum system evacuated by ion and titanium sublimation pumps ( p=5 × 10 -9 torr) and deposited at rates ranging from 2.5 Å/sec to 500 Å/sec. For aluminum deposited at rates of 300 Å /sec and greater there is no measurable difference in the visible and ultraviolet reflectance of the two types of films. However, if lower deposition rates are used the reflectance of aluminum films deposited at 5 x 10 -9 torr is much less dependent on deposition rate than that of films condensed at 3 x 10 -6 torr. Aluminum films deposited at high rates, both in conventional and ultra-high vacuum systems, show less degradation of reflectance during exposure to air than the films deposited at low rates.