Grineviciute, L.; Ng, S.H.; Han, M.; Moein, T.; Anand, V.; Katkus, T.; Ryu, M.; Morikawa, J.; Tobin, M.J.; Vongsvivut, J.; Tolenis, T.; Juodkazis, S. Anisotropy of 3D Columnar Coatings in Mid-Infrared Spectral Range. Nanomaterials2021, 11, 3247.
Grineviciute, L.; Ng, S.H.; Han, M.; Moein, T.; Anand, V.; Katkus, T.; Ryu, M.; Morikawa, J.; Tobin, M.J.; Vongsvivut, J.; Tolenis, T.; Juodkazis, S. Anisotropy of 3D Columnar Coatings in Mid-Infrared Spectral Range. Nanomaterials 2021, 11, 3247.
Polarisation analysis in the mid-infrared fingerprint region was carried out on thin (∼1μm) Si and SiO2 films evaporated via glancing angle deposition (GLAD) method at 70∘ 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 the cos2θ angular 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.
This is an open access article distributed under the Creative Commons Attribution License which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.