Large-area fabrication of TiN nanoantenna arrays for refractory plasmonics in the mid-infrared by femtosecond direct laser writing and interference lithography [Invited]

Abstract

Robust plasmonic nanoantennas at mid-infrared wavelengths are essential components for a variety of nanophotonic applications ranging from thermography to energy conversion. Titanium nitride (TiN) is a promising candidate for such cases due to its high thermal stability and metallic character. Here, we employ direct laser writing as well as interference lithography to fabricate large-area nanoantenna arrays of TiN on sapphire and silicon substrates. Our lithographic tools allow for fast and homogeneous preparation of nanoantenna geometries on a polymer layer, which is then selectively transferred to TiN by subsequent argon ion beam etching followed by a chemical wet etching process. The antennas are protected by an additional Al 2 O 3 layer which allows for high-temperature annealing in argon flow without loss of the plasmonic properties. Tailoring of the TiN antenna geometry enables precise tuning of the plasmon resonances from the near to the mid-infrared spectral range. Due to the advantageous properties of TiN combined with our versatile large-area and low-cost fabrication process, such refractory nanoantennas will enable a multitude of high-temperature plasmonic applications such as thermophotovoltaics in the future.

Broadband Hot‐Electron Collection for Solar Water Splitting with Plasmonic Titanium Nitride

“…On the other hand, transition metal nitrides such as titanium nitride (TiN) and zirconium nitride have recently been proposed as plasmonic materials that exhibit gold‐competitive optical properties while also offering compatibility with CMOS technology, thermal and chemical stability, corrosion resistance, as well as improved mechanical strength and durability in comparison to noble metals . For instance, TiN has been shown to exhibit superior performance in local heating and in extremely high temperature applications such as heat‐assisted magnetic recording and solar/thermo‐photovoltaics .…”

Large‐Area Ultrabroadband Absorber for Solar Thermophotovoltaics Based on 3D Titanium Nitride Nanopillars

“…Titanium nitride (TiN) has recently emerged as an alternative refractory plasmonic material and gained enormous interest due to high thermal stability, chemical stability, mechanical hardness, and CMOS compatibility . TiN provides unique optical properties in the visible to mid‐infrared regime, and the optical losses of TiN are strongly dependent on process temperature and deposition conditions .…”

“…Titanium nitride (TiN) has recently emerged as an alternative refractory plasmonic material and gained enormous interest due to high thermal stability, chemical stability, mechanical hardness, and CMOS compatibility . TiN provides unique optical properties in the visible to mid‐infrared regime, and the optical losses of TiN are strongly dependent on process temperature and deposition conditions . TiN is one of the highly investigated transition‐metal nitrides with optical properties similar to Au, and its potential applications are in solar heat transducers, solar water splitting, hot electron excitation, broadband photodetectors, waveguiding, modulators, nonlinear optical devices, and particularly in high‐temperature applications, such as, STPV (broadband absorber and thermal emitter) .…”

“…TiN is one of the highly investigated transition‐metal nitrides with optical properties similar to Au, and its potential applications are in solar heat transducers, solar water splitting, hot electron excitation, broadband photodetectors, waveguiding, modulators, nonlinear optical devices, and particularly in high‐temperature applications, such as, STPV (broadband absorber and thermal emitter) . However, the applicability of TiN material in plasmonics is significantly limited by the tedious high‐temperature fabrication procedure, and the use of lithography tools (e‐beam and laser interference lithography) is expensive and time‐consuming, and cannot currently be realized to wafer‐scale fabrication methods . A key challenge is to achieve such substrates by cost‐effective mass production approaches.…”

Fabricating Three‐Dimensional Periodic Micro Patterns on Photo‐Resists Using Laser Interference Lithography

“…The undercut helps to prevent adhesion of the metal pattern to the lithographic mask, while the etching mask can be patterned by various methods such as nanoimprint, UV, and E‐beam lithography . In the case of periodic (repetitive) patterns, laser interference lithography can also be utilized to effectively treat large surfaces without the use of cost‐intensive masks . As an alternative, lift‐off processes can be used for undercut formation without silicon etching.…”