Optical anisotropy of glancing angle deposited thin films on nano-patterned substrates

Abstract

This study has demonstrated that 3D columnar micro-films/coatings can be deposited over pre-patterned surfaces with sub-micrometer periodic patterns. Four-angle polarisation analysis of thin (0.4 − 1~μm) Si and SiO2 films, evaporated via glancing angle deposition (GLAD) at 70° to the normal, was carried out in reflection mode using synchrotron infrared microspectroscopy at the Australian Synchrotron. The angular dependence of absorbance followed A(θ) ∝ cos 2θ, confirmed for Si substrates patterned by electron beam lithography and plasma etching, which were used to make checkerboard patterns of Λ = 0.4~μm period on Si. Retardance control by birefringence of a patterned SiO2 substrate coated by columnar SiO2 is promising for UV-visible applications due to the use of the same material to endow polarisation control.