Anisotropic 3D columnar micro-film coating for applications in infrared and visible spectral ranges

Polarisation analysis of thin (similar to 1 mu m) SiO2 films deposited via evaporation at a glancing angle of 70 degrees to the normal on resist pillar arrays was carried out using synchrotron-based Fourier transform infrared (s-FTIR) microspectroscopy in reflection mode. Changes in intensity of absorption bands were observed to follow the angular dependence of similar to cos(2)theta, consistent with the absorption anisotropy. The strongest absorption was found to be the sharp Si-O-Si stretching vibrational mode at 1040 +/- 20 cm(-1), which can be used for sensor applications, as well as radiative cooling in the atmospheric transparency window, within the range of 8-13 mu m (i.e. 1250-769 cm(-1)). Anisotropy of IR absorbance is correlated with retardance/birefringence of the same patterns in the visible spectral range. Larger period patterns of 3D columnar SiO2 films of similar to 1 mu m in thickness deposited on polymer/resist pillar arrays provide the possibility to control anisotropy of the form-birefringent 3D columnar films.

Automated summary

The polarization analysis of thin SiO2 films deposited on resist pillar arrays was conducted using synchrotron-based FTIR microspectroscopy. It was found that the changes in absorption band intensity followed the angular dependence of cos(2)theta, indicating absorption anisotropy. The study also identified the strongest absorption peak at 1040 +/- 20 cm(-1), which has potential applications in sensor technology and radiative cooling.