Macroscopic surface roughness in metal-dielectric composite films: Photothermal absorber applications

Abstract

Previous studies have shown that coevaporated metal-dielectric composite films are quite smooth. But a substantially higher deposition temperature results in the surface roughness of Mo/Al2O3 composite films becoming larger than the mean film thickness. This effect was applied to photothermal solar absorbers where, for the first time, a stable selective absorber was produced which absorbs over 99% of the solar spectrum. These results have implications for other surface roughness dependent effects.