Mid-infrared nanospectroscopy of Berreman mode and epsilon-near-zero local field confinement in thin films

Thin films with vanishing real part of the dielectric function Re[ amp; 949;] 0 in the mid infrared MIR region are promising photonic materials for manipulating and enhancing IR light matter interactions at the nanoscale. We present a nanospectroscopic characterization of two fundamental polaritonic phenomena near Re[ amp; 949;] 0 by atomic force microscope infrared spectroscopy AFM IR the Berreman mode BE in 100 nm SiO2 and Si3N4 films on Si, and epsilon near zero ENZ local field confinement in a 2 nm native SiO2 layer on Si. AFM IR is an emerging photothermal technique that provides direct information on nanoscale IR absorption, allowing unambiguous identification of BE and ENZ effects supported by simulations. We demonstrate far field applicability of polaritonic AFM IR studies by characterizing a nanoscale plasmonic ENZ grating on Si with 2 nm native SiO2 using polarization dependent IR microscopy