Optical Properties and Stability of Copper Thin Films for Transparent Thermal Heat Reflectors

Abstract

The use of thin metallic layers at the thickness limit where transparency or spectral selectivity are achieved is gaining increased interest. The use of cheap and abundant materials is desirable in the attempt to avoid environment or economical costs. The use of Cu as a replacement for Ag as a heat reflector is one of the solutions that can be employed. The stability over time is a known issue, copper being prone to atmospheric oxidation and degradation. In this contribution, the stability of Cu obtained by magnetron sputtering is investigated, using both DC and HiPIMS processes for obtaining the Cu thin films. The bias voltage is used to obtain thin films with different properties, their time stability being investigated through the variation of spectrophotometric curves. The best performing thin films are evaluated in theoretical heat reflector structures, using SiNx of different qualities as dielectric layers to form the dielectric/metal/dielectric structure.