Transparent
conducting oxides (TCOs) are emerging as possible alternative
constituent materials to replace noble metals such as silver and gold
for low-loss plasmonic applications in the near-infrared (NIR) and
mid-infrared (MIR) regimes. In particular, TCO-based nanostructures
are extensively investigated for biospectroscopy exploiting their
surface-enhanced infrared absorption (SEIRA). The latter enhances
the absorption from vibrational and rotational modes of nearby biomolecules,
making TCO nanostructures a promising candidate for IR sensing applications.
Nevertheless, in order to produce inexpensive devices for lab-on-a-chip
diagnostics, it would be favorable to achieve surface-enhanced infrared
absorption with very simple microstructures not requiring nanosize
control. In this work, we attempt to demonstrate a SEIRA effect with
the least challenging fabrication, μm-scale instead of nm-scale,
by tailoring both device design and charge density of the indium tin
oxide (ITO) film. We show that microperiodic hole arrays in a ITO
film are able to produce SEIRA via grating coupling. Such a study
opens the way for innovative and disrupting biosensing devices
