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

Lina Grineviciute; Soon Hock Ng; Molong Han; Tania Moein; Vijayakumar Anand; Tomas Katkus; Meguya Ryu; Junko Morikawa; Mark J Tobin; Jitraporn Vongsvivut; Tomas Tolenis; Saulius Juodkazis

doi:10.3390/nano11123247

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

Nanomaterials (Basel). 2021 Nov 29;11(12):3247. doi: 10.3390/nano11123247.

Authors

Lina Grineviciute¹, Soon Hock Ng^{2

3}, Molong Han², Tania Moein², Vijayakumar Anand², Tomas Katkus², Meguya Ryu^{4

5}, Junko Morikawa^{5

6}, Mark J Tobin⁷, Jitraporn Vongsvivut⁷, Tomas Tolenis^{1

8}, Saulius Juodkazis^{2

3

6}

Affiliations

¹ Center for Physical Sciences and Technology, Savanoriu̧ Ave. 231, LT-02300 Vilnius, Lithuania.
² Optical Sciences Centre and ARC Training Centre in Surface Engineering for Advanced Materials (SEAM), School of Science, Swinburne University of Technology, Hawthorn, VIC 3122, Australia.
³ Melbourne Centre for Nanofabrication (MCN), Australian National Fabrication Facility, Clayton, VIC 3168, Australia.
⁴ Research Institute for Material and Chemical Measurement, National Metrology Institute of Japan (AIST), Tsukuba Central 3, 1-1-1 Umezono, Tsukuba 305-8563, Japan.
⁵ CREST-JST and School of Materials and Chemical Technology, Tokyo Institute of Technology, 2-12-1, Ookayama, Meguro-ku, Tokyo 152-8550, Japan.
⁶ World Research Hub Initiative (WRHI), School of Materials and Chemical Technology, Tokyo Institute of Technology, 2-12-1, Ookayama, Meguro-ku, Tokyo 152-8550, Japan.
⁷ Infrared Microspectroscopy (IRM) Beamline, ANSTO-Australian Synchrotron, 800 Blackburn Road, Clayton, VIC 3168, Australia.
⁸ ELI Beamlines, Institute of Physics, The Czech Academy of Sciences, Za Radnicí 835, 252 41 Dolní Břežany, Czech Republic.

Abstract

Polarisation analysis in the mid-infrared fingerprint region was carried out on thin (∼1 μm) 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.

Keywords: IR; anisotropy; birefringence; dichroism; fingerprint region; polarisation; sculptured thin films.

Abstract

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