Preparation and Characterization of Solar Thermal Absorbers by Nanoimprint Lithography and Sputtering

Selective solar absorbers comprised of plasmonic materials offer great flexibility in design along with a highly promising optical performance. However, the nanopattern generation, typically done with electron beam writing, is a very time-intensive process. In this work, we present a fast, scalable, and flexible method for the fabrication of plasmonic materials by the combination of a deposition mask prepared by nanoimprint lithography and thin film deposition by magnetron sputtering. The fabrication process was first performed on silicon wafer substrates using AFM and SEM measurements to calibrate the deposition time, determine maximal deposition height, and characterize samples. Afterwards, the process was transferred to polished Inconel NiCr-alloy substrates used in high temperature solar absorbers. To investigate the adhesion properties of the nanostructure on the substrate, two different deposition methods were investigated: DC magnetron sputtering and High Power Impulse Magnetron Sputtering (HiPIMS).