Titanium Oxynitride Thin Films with Tunable Double Epsilon-Near-Zero Behavior for Nanophotonic Applications

Abstract

Titanium oxynitride (TiON) thin films are fabricated using reactive magnetron sputtering. The mechanism of their growth formation is explained, and their optical properties are presented. The films grown when the level of residual oxygen in the background vacuum was between 5 nTorr to 20 nTorr exhibit double epsilon-near-Zero (2-ENZ) behavior with ENZ1 and ENZ2 wavelengths tunable in the 700-850 and 1100-1350 nm spectral ranges, respectively. Samples fabricated when the level of residual oxygen in the background vacuum was above 2 × 10 Torr exhibit nonmetallic behavior, while the layers deposited when the level of residual oxygen in the background vacuum was below 5 × 10 Torr show metallic behavior with a single ENZ value. The double ENZ phenomenon is related to the level of residual oxygen in the background vacuum and is attributed to the mixture of TiN and TiON and TiO phases in the films. Varying the partial pressure of nitrogen during the deposition can further control the amount of TiN, TiO, and TiON compounds in the films and, therefore, tune the screened plasma wavelengths. A good approximation of the ellipsometric behavior is achieved with Maxwell-Garnett theory for a composite film formed by a mixture of TiO and TiN phases suggesting that double ENZ TiON films are formed by inclusions of TiN within a TiO matrix. These oxynitride compounds could be considered as new materials exhibiting double ENZ in the visible and near-IR spectral ranges. Materials with ENZ properties are advantageous for designing the enhanced nonlinear optical response, metasurfaces, and nonreciprocal behavior.

Plasma Enhanced Atomic Layer Deposition of Plasmonic TiN Ultrathin Films Using TDMATi and NH3

“…The slope of ε 1 in the visible region is similar to ultrathin TiN on MgO in the region of 500-900 nm, though the TiN shows dielectric behavior (a flattening of ε 1 ) at wavelengths over 900 nm. This is, in part, attributed to the oxygen composition in the TiN, and is consistent with previous findings of TiN thin films on silicon with oxygen contents between 10% and 25% [10,35]. With the post-deposition plasma treatment this flattening of ε 1 is reduced, consistent with Yun et al findings that such treatments reduce surface oxidation [30] The slope and position of ε 1 indicate a broad plasmon resonance centered at 586 nm, with a corresponding ε 2 value of 4.21.…”

Interband transitions in semi-metals, semiconductors, and topological insulators: a new driving force for plasmonics and nanophotonics [Invited]

“…Moreover, it is also very probable that similar optical properties can be found in compounds involving non p-block elements, or even without any p-block element at all. We can cite here very recent reports by Yan et al and Braic et al [106,107] who demonstrated plasmonic effects at visible photon energies in substoechiometric titanium oxide and titanium oxynitrides, respectively. In the first case, an interband plasmonic origin was claimed for the resonances.…”

Enhancement of the Corrosion Resistance of 304 Stainless Steel by Cr–N and Cr(N,O) Coatings

“…Different TM nitride coatings have been synthesised and investigated due to their high hardness, good oxidation resistance, and low wear rate in dry atmosphere, as well as their phase stability in corrosive environments [10,15,[33][34][35][36][37]. Oxynitride coatings have also been studied due to their plasmonic properties, relatively low electrical resistivity, good biocompatibility, and high oxidation resistance [25,[38][39][40][41][42][43][44][45][46].…”