Electron beam lithography for high density meta fish scale operational at optical frequency

Abstract

This paper reports our recent progress in electron beam lithography for high resolution and highly dense metallic structures such as fish scale on both silicon and quartz. To observe photonic property in optical frequency, the pitch of 500 nm with both linewidth and gap of 50 nm gap in Al is demanded. For reliable lift-off process, adequate undercut in bilayer layer of resists is essential. Three different bilayers, PMMA/LOR, PMMA/copolymer and PMMA/PMMA (with different molecular weights) were compared and the most suitable bilayer was found to be the PMMA/PMMA with a difference in molecular weight between the top and bottom layer. With such a bilayer stack, dense fish scale pattern with minimum linewidth of 50 nm in Al were fabricated for both transparent and reflective configurations. Astonishing optical properties such as magnetic wall and asymmetric propagating waves through the chiral fish scale were observed.

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Identifiers

ORCID for Nikolay I. Zheludev: orcid.org/0000-0002-1013-6636

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