A sputtered copper-carbon selective absorbing surface for evacuated collectors

Abstract

A new sputtered selective surface for use in evacuated collectors is described. The surface, consisting of a graded copper-carbon cermet on a copper base layer, is produced by non-reactive sputtering in argon, and reactive sputtering in argon and acetylene, of a single copper electrode. Optical properties of the surface change slightly after bakeout in vacuum for ≈ 1 h at 500°C. Auger depth profiling of the surface before and after bakeout indicates that diffusion of copper occurs in the film during bakeout. The surface exhibits absorptance 0.94 and emittance 0.04 (at 120°C) in a completely assembled evacuated collector. The requirement of a single sputter electrode results in relatively simple construction and operation of a sputtering for coating batches of glass tubes.