Published

(School of Materials and Chemical Technology / Dr. Junko Morikawa and Dr. Saulius Juodkazis)

“Anisotropy of 3D Columnar Coatings in Mid-Infrared Spectral Range”

Nanomaterials （DOI:10.3390/nano11123247）

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<Abstract>
Polarisation analysis in the mid-infrared fingerprint region was carried out on thin (∼1μm) Si and SiO₂films evaporated via glancing angle deposition (GLAD) method at70∘to the normal. Synchrotron-based infrared microspectroscopic measurements were carried out on the Infrared Microspectroscopy (IRM) beamline at Australian Synchrotron. Specific absorption bands, particularly Si-O-Si stretching vibration, was found to follow the angular dependence of ∼cos2θ, consistent with the absorption anisotropy. This unexpected anisotropy stems from the enhanced absorption in nano-crevices, which have orientation following thecos2θangular dependence as revealed by Fourier transforming the image of the surface of 3D columnar films and numerical modeling of light field enhancement by sub-wavelength nano-crevices.