Direct fabrication of a metal-like TiN-based plasmonic grating using nitridation of a photo-patternable TiO_2 sol-gel film

We propose to combine a few known technologies to print TiOxNy quasi-sinusoidal grating using a direct photo-patternable TiO2 sol-gel thin layer, enabling the conversion of a pure dielectric grating to a metallic one. An expanded laser beam illuminates a photosensitive TiO2 sol-gel layer through a photo-mask grating, creating illuminated and non-illuminated areas in the sol-gel layer, which act as a negative photoresist and leads to a TiO2 based grating. Nitridation is made by heat treatment under NH3 flow to convert TiO2 in TiOxNy grating. This process shows that the sol-gel technology can be extended from a dielectric to metallic layer. The derived meta-material offers an alternative for plasmonic effects in the near-infrared region. This paper describes the experimental processes from the photochemistry of the TiO2 sol-gel layer to its nitridation. Thanks to the optical properties of the obtained micrometric period TiOxNy grating, surface plasmon resonance at TiOxNy-air interface has been excited in the NIR range (around 1500 nm), demonstrating the metallic behavior of the grating and its ability to be used as a plasmonic component.