Characterization of Chiral Nanostructured Surfaces Made via Colloidal Lithography

Optically anisotropic materials were produced via colloidal lithography and characterized using scanning electronic microscopy (SEM), confocal microscopy, and polarimetry. A compact hexagonal array mask composed of silica sub-micron particles was fabricated via the Langmuir-Blodgett self-assembly technique. Subsequently, the mask pattern was transferred onto monocrystalline silicon and commercial glass substrates using ion beam etching in a vacuum. Varying the azimuthal angle while etching at oblique incidence carved screw-like shaped pillars into the substrates, resulting in heterochiral structures depending on the azimuthal angle direction. To enhance the material's optical properties through plasmon resonance, gold films were deposited onto the pillars. Polarimetric measurements were realized at normal and oblique incidences, showing that the etching directions have a clear influence on the value of the linear birefringence and linear dichroism. The polarimetric properties, especially the chiroptical responses, increased with the increase in the angle of incidence.

Automated summary

Optically anisotropic materials form through colloidal lithography were studied using SEM, confocal microscopy, and polarimetry. A hexagonal array mask made of sub-micron silica particles was created via Langmuir-Blodgett self-assembly, and the pattern was transferred onto silicon and glass substrates using ion beam etching. Gold films were then deposited onto the etched pillars to enhance optical properties. Polarimetric measurements showed that the etching directions influenced the linear birefringence and linear dichroism, with the chiroptical responses increasing with the angle of incidence.