Versatile Micro and Nano Patterning Technique for TiO2 and TiN-Based Sol–Gel Thin Films

International audienc

Versatile Micro and Nano Patterning Technique for TiO2 and TiN-Based Sol–Gel Thin Films

International audienc

Micro–Nanostructured TiN Thin Film: Synthesis from a Photo-Patternable TiO2 Sol–Gel Coating and Rapid Thermal Nitridation

International audienceThe miniaturization of optical components to control and manipulate light amplitude, phase, and polarization requires micro-to nanostructured metasurfaces that provide resonant light−matter interactions to exploit optical properties in the visible and near-infrared (NIR) range (plasmonic resonances, wavelength filtering, etc.). Such metasurfaces sometimes need to be implemented under hard-use conditions, including high temperatures and strong field confinement. Transition-metal nitrides, like titanium nitride (TiN), are ideal materials to achieve such properties, but TiN's hardness and chemical inertness make patterning difficult. Here, we present an innovative direct fabrication process to easily synthesize a micro−nanostructured TiN thin film. The technological process is based on a direct photo-patternable titanium oxide TiO 2 sol−gel layer converted into TiN with a rapid thermal nitridation process. The nanoarchitecture and chemical composition of TiO 2 and TiN films were investigated by ultraviolet (UV)− visible−infrared (IR) spectroscopy and Raman spectroscopy, grazing incidence X-ray diffraction (GIXRD), and high-resolution transmission electron microscopy (HRTEM) coupled with electron energy loss spectroscopy (EELS). We obtained micro−nanotextured crystallized TiN surfaces in a significantly shorter time than with conventional nitridation processes. Due to the sol−gel approach, this work also significantly extends the chances of obtaining TiNbased metasurfaces on various substrates (glasses, plastics, etc.) in complex shapes (non-planar-based surfaces), for demanding photonic applications in the future

Synthesis of micro-nanostructured TiN thin film from a TiO2 sol–gel

International audienc

Synthesis of micro-nanostructured TiN thin film from a TiO2 sol–gel

International audienc

Fabrication of a Resonant Waveguide Grating (RWG) with a single-step TiO2 sol-gel technological approach on planar and non-conventional substrate (cylinder)

International audienc

Fabrication of a Resonant Waveguide Grating (RWG) with a single-step TiO2 sol-gel technological approach on planar and non-conventional substrate (cylinder)

International audienc

Photonic crystal backbone for light trapping inside an ultrathin, low absorbing layer

International audienceA few tens of nanometre thick ultrathin materials may suffer from a very low absorption at their band edges. In this work, we investigate a photonic crystal (PC) made of a lowcost, transparent patterned silicon nitride (SiN x ) layer, conformally covered with an ultrathin active layer (e.g., 20 nm TiO 2 ) in view of its use in various applications such as photocatalysis. A fair estimation of the absorption enhancement, considering the volume of the active material, is calculated using RCWA. A remarkable enhancement (more than ten-folds) in absorptance in the near UV range and a very high transmittance over the visible range are observed. A detailed modal analysis of the structures-of-interest unravels the Light Trapping (LT) mechanisms and allows the derivation of key design guidelines. Optical measurements on a patterned sample provide a first proof-of-concept of such possible photonic backbone structures suitable for highly efficient depollution and artificial photosynthesis for solar fuels production

Resonant waveguide grating fabrication on planar and cylindrical substrates using a photosensitive TiO2 sol-gel approach

International audienceA single-step sol-gel technological approach combining sol-gel layer development and UV lithography is demonstrated for the fabrication of resonant waveguide gratings (RWG) on planar and cylindrical substrates. The aim of this article is the demonstration of a resonant reflection in TE and TM polarization in the near-infrared region (NIR) in a planar and in cylindrical-based resonant waveguide gratings (RWG). In this work, we start with a planar corrugated waveguide structure excited by a planar wave and demonstrate this concept to a circularly symmetrical waveguide applied to the inside wall of an 8 mm diameter tube, excited by a cylindrical wave. For both configurations, the same TiO 2 sol-gel layer is used for the high index waveguide layer and for the grating printing thanks to the UV photosensitivity property of the sol-gel layers, avoiding any etching processes. The reflection spectrum was measured in the near-infrared range and compared to the modeling, showing the expected resonant behavior

Two‐dimensional photonic metasurfaces for slow light‐controlled photocatalysis

International audiencePhotocatalysis using semiconductor materials like titania (TiO 2) is a key method for environmental purification or solar fuel generation. Nanostructures that maximize incident light absorption are highly desired to enhance depollution rate or solar-to-fuel conversion efficiency in limited volumes of catalysts. Here, we report on structural and optical properties of metasurfaces based on a 20 nm thick anatase layer conformally deposited onto a wavelength-scale two-dimensional periodic photonic lattice. We investigate the NO degradation using such metasurfaces, and evaluate the impact of the patterning on photocatalytic activities between 340 and 400 nm. In the 380-385 nm range, the mean photochemical efficiency is increased by a factor up to 5.7 compared to flat references, with an overall threefold enhancement within the whole spectral range of interest. This approach can be applied to numerous types of systems by varying active materials, leading to substantial improvements in air/water depollution, water splitting or artificial photosynthesis processes