Enhanced selective solar absorption of surface nanotextured semi-insulating 6H–SiC.

Surface treatments were performed on single-crystal semi-insulating 6H–SiC by femtosecond pulsed laser irradiation, aimed at analyzing the effect of the laser-induced periodic surface structures (LIPSSs) on the films' optical properties. The surface morphology study of the laser-induced nanostructures allows determining the modification threshold fluence of about 0.7 J cm−2 as well as detecting fine (160 nm) and coarse (450–550 nm) ripples according to different values of the laser pulse fluence (Φ P) released to the material. Micro-Raman spectroscopy allows determining the presence of undesired amorphous structural phases when Φ P exceeds 2.15 J cm−2, whereas no compositional variations occur for lower values of Φ P. Samples treated on the entire surface with the pulse fluence conditions to obtain fine ripples were optically tested. Although the long-range order is progressively lost as the accumulated laser fluence increases, the heaviest treated samples show solar absorptance values > 75% and spectral selectivity up to 1.7 projected at the operating temperature of 1000 K, thus pointing out the suitability of fs-laser surface textured 6H–SiC to act as a selective solar absorber for energy conversion devices operating at high temperature. Image 1 • Single-crystal 6H-SiC films have been surface nanotextured with fs- laser pulses. • The modification threshold laser fluence has been found to be around 0.7 J/cm2. • Solar absorptance has shown a maximum value >75%. • Solar selectivity has reported the significant values of 1.7 at 1000 K. [ABSTRACT FROM AUTHOR]