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Black and white fused silica: Modified sol-gel process combined with moth-eye structuring for highly absorbing and diffuse reflecting SiO2 glass

: Brunner, R.; Kraus, M.; Hirte, J.; Diao, Z.; Weishaupt, K.; Spatz, J.P.; Harzendorf, T.; Trost, M.; Munser, A.S.; Schröder, S.; Bär, M.

Volltext ()

Optics Express 28 (2020), Nr.22, S.32499-32516
ISSN: 1094-4087
Zeitschriftenaufsatz, Elektronische Publikation
Fraunhofer IOF ()
Block Copolymery; carbon black; micelles; reactive ion etching; reflection

Diffuse reflecting (white) and highly absorbing (black) fused silica based materials are presented, which combine volume modified substrates and surfaces equipped with antireflective moth-eye-structures. For diffuse reflection, micrometer sized cavities are created in bulk fused silica during a sol-gel process. In contrast, carbon black particles are added to get the highly absorbing material. The moth-eye-structures are prepared by block copolymer micelle nanolithography (BCML), followed by a reactive-ion-etching (RIE) step. The moth-eye-structures drastically reduce the specular reflectance on both diffuse reflecting and highly absorbing samples across a wide spectral range from 250 nm to 2500 nm and for varying incidence angles. The adjustment of the height of the moth-eye-structures allows us to select the spectral position of the specular reflectance minimum, which measures less than 0.1%. Diffuse Lambertian-like scattering and absorbance appear nearly uniform across the selected spectral range, showing a slight decrease with increasing wavelength.