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Polarisation analysis in the mid-infrared fingerprint region was carried out on thin (∼1 <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mi mathvariant="sans-serif">μ</mi></semantics></math></inline-formula>m) Si and SiO₂ films evaporated via glancing angle deposition (GLAD) method at <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mrow><mspace width="3.33333pt"></mspace><msup><mn>70</mn><mo>∘</mo></msup></mrow></semantics></math></inline-formula> 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 ∼<inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mrow><msup><mo form="prefix">cos</mo><mn>2</mn></msup><mi>θ</mi></mrow></semantics></math></inline-formula>, consistent with the absorption anisotropy. This unexpected anisotropy stems from the enhanced absorption in nano-crevices, which have orientation following the <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mrow><msup><mo form="prefix">cos</mo><mn>2</mn></msup><mi>θ</mi></mrow></semantics></math></inline-formula> 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.