Preservation of far-UV aluminum reflectance by means of overcoating with C₆₀ films

José A. Méndez, Juan I. Larruquert, and José A. Aznárez

Abstract

Thin films of C₆₀ were investigated as protective coatings of Al films to preserve their far-UV (FUV) reflectance by inhibition or retardation of their oxidation. Two methods were used for the overcoating of Al films with approximately one monolayer of C₆₀: (1) deposition of a multilayer film followed by temperature desorption of all but one monolayer and (2) direct deposition of approximately one-monolayer film. We exposed both types of sample to controlled doses of molecular oxygen and water vapor and measured their FUV reflectance before and after exposure to evaluate the achieved protection on the Al films. The whole process of sample preparation, reflectance measurement, sample heating, and oxidation was made without breaking vacuum. Results show that a C₆₀ monolayer protected Al from oxidation to some extent, although FUV reflectance of unprotected Al films was never exceeded. FUV optical constants of C₆₀ films and the FUV reflectance of the C₆₀ film as deposited and as a function of exposure to O₂ were also measured.