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 Al2O3 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.
Highlights
Plasmonics is at the heart of many aspects of nano-optics and photonics, where it has been utilized for a broad variety of research and commercial applications
Materials which undergo a phase change in response to an external stimulus such as vanadium dioxide (VO2) [14], germanium antimony telluride (GST) [15], yttrium (Y) [16] and magnesium [17] have been employed to realize active plasmonic devices. Another crucial material-related challenge is the stability of plasmonic structures at the very high temperatures that are relevant to many industrial processes
The fabricated nanoantennas provide a plasmon resonance which is strongly dependent on the antenna material and the dielectric function of the Titanium nitride (TiN) film
Summary
Plasmonics is at the heart of many aspects of nano-optics and photonics, where it has been utilized for a broad variety of research and commercial applications. Materials which undergo a phase change in response to an external stimulus such as vanadium dioxide (VO2) [14], germanium antimony telluride (GST) [15], yttrium (Y) [16] and magnesium [17] have been employed to realize active plasmonic devices Another crucial material-related challenge is the stability of plasmonic structures at the very high temperatures that are relevant to many industrial processes. We utilize fast and wafer-scale fabrication methods such as direct laser writing (DLW) [27] and laser interference lithography (LIL) [28] to create a regular polymer pattern, which is selectively transferred into a TiN layer through a combination of dry and chemical wet etching processes Following this approach, we achieve large-area nanoantenna arrays of TiN with tunable plasmon resonances from the near- to the mid-infrared spectral range. Due to the refractory properties of TiN, the fabricated nanoantennas are good candidates for high-temperature plasmonic applications, when covered with an oxide-resistant layer with high-temperature stability such as Al2O3 or Si3N4
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