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

Abstract

The 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.

Optical, electrical and mechanical properties of TiN thin film obtained from a TiO2 sol-gel coating and rapid thermal nitridation

“…After nitration of TiO 2 sol-gel by RTN treatment, the thin film obtained, shown in Fig. 1 with results reported in previous works [24]. The 210, 318, 447 and 526 cm − 1 bands observed in the spectrum relate to transverse acoustic (TA), longitudinal acoustic (LA), second-order acoustic (2A) and transverse optical (TO) modes respectively.…”

“…To conclude from these ellipsometry results, we observe a lower metallic behavior in our TiN film compared to recent reports of plasmonic TiN [21,31], which can be attributed, as discussed above, to the residual porosity due to the preparation method, and thus explains the lower conductivity of the metallic TiN films as discussed previously. However, as mentioned in our previous work [24], these results show that the TiN layer, obtained using a particularly simplified and low cost method, could be potentially used as a plasmonic layer in the NIR range, with reasonably losses. These has been demonstrated by the reflection spectrum of the TM polarized incident beam with a dip in the reflection curve attributed to the excitation of a Surface Plasmon mode, propagating along the metallic layer.…”

“…The film presents the lowest real permittivity around ε ′ ≈ − 30 for λ = 2000 nm. Generally, the metallic property is estimated with the absolute value of the real part of the permittivity (ε ′ ) and must be as high as possible to consider a good noted that these optical results for TiN are also quite similar to those obtained in previous work [24] while the NH 3 flux used during the nitridation process has been divided by two. To conclude from these ellipsometry results, we observe a lower metallic behavior in our TiN film compared to recent reports of plasmonic TiN [21,31], which can be attributed, as discussed above, to the residual porosity due to the preparation method, and thus explains the lower conductivity of the metallic TiN films as discussed previously.…”

“…In a previous work, we have shown that this method can be implemented by performing micronano structuring on a photopatternable TiO 2 sol-gel film, deposited from a photosensitive sol, that is then converted into micro-nanostructured TiO x N y using a high temperature thermal nitridation process in an ammoniac atmosphere [23]. More recently, we have presented an innovative and direct rapid thermal nitridation (RTN) process allowing us to obtain micro-nanotextured crystallized TiN surfaces in significantly less stringent conditions [24]. RTN appears to be a very promising alternative way to synthetize high-quality submicro-structured TiN thin films with complex shapes on a wide range of substrates.…”

Metal nitride-based nanostructures for electrochemical and photocatalytic hydrogen production

“…H 2 O, NaOH, HCl, NF Hydrothermal 100 Hexagonal, nanosheet [ 72 ] Thermal annealing under NH 3 380 Ni 3 N/C cloth composite Ni(NO 3 ) 2. 6H 2 O, HNO 3 Hydrothermal 120 3D, nanosheet [ 73 ] Thermal annealing under NH 3 400 PdN Na 2 PdCl 4 , C 6 H 8 O 6 ,AA, PVP (Polyvinylpyrrolidone), KBr Hydrothermal-Nitridation 180 Nanocubes [ 74 ] TiN Ti(C 4 H 9 O) 4 , C 3 H 8 O, C 3 H 8 O 3 Solvothermal 180 2D, leaf-like nanorods [ 75 ] Thermal annealing in air 450 CVD under NH 3 800 TiN Sol 1 – TIPT, BzAc, MeOH Sol-gel thermal nitridation 110 Cubic [ 76 ] Sol 2 – TIPT, H 2 O, HCl, BuOH WN WO 3 , NaCl, SiO 2 /Si CVD under NH 3 800 2D nanosheet [ …”