Titanium Nitride Epitaxial Films as a Plasmonic Material Platform: Alternative to Gold

Abstract

Titanium nitride (TiN) is an interesting refractory metallic compound which could replace gold as an alternative plasmonic material, especially for high temperature and semiconductor compatible applications. However, reported plasmonic properties of TiN films are so far limited by conventional growth techniques, such as reactive sputtering. In this work, we adopt the nitrogen-plasma-assisted molecular-beam epitaxy (MBE) to grow single-crystalline, stoichiometric TiN films on sapphire substrates. The properties of as-grown TiN epitaxial films have been fully characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), spectroscopic ellipsometry (SE), and surface plasmon polariton (SPP) interferometry. We have confirmed that MBE-grown TiN films exhibit excellent plasmonic properties to replace gold in the visible and near-infrared spectral regions. Measuring the real and imaginary parts of dielectric function by SE, it is also found that TiN is better than gold in the shortwavelength range (<500 nm), where gold suffers from strong loss due to interband transition. Contrary to the recent theoretical prediction that air is not able to stabilize SPP modes at the TiN surface, our surface plasmon interferometry data clearly show the presence of propagating SPP modes at the TiN/air interface. To demonstrate the unique plasmonic properties of MBEgrown stoichiometric TiN, we have fabricated TiN metasurfaces for the visible-spectrum applications.

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

“…Indeed, TiN has intrinsic physico-chemical and optical properties making it first-choice material: low resistivity, high reflectance in the infrared spectral range, good corrosion resistance, good chemical inertness, good thermal stability, and high hardness [4][5][6]. Generally, TiN thin layer is obtained using a wide range of deposition processes requiring vacuum technology, such as reactive magneton sputtering [1,[7][8][9][10], molecular-beam epitaxy [11,12], chemical vapor deposition (CVD) [13][14][15], atomic layer deposition (ALD) [16][17][18][19] or pulsed laser deposition (PLD) [20][21][22], under a nitrogen or ammonia atmosphere. Unfortunately, due to its good hardness and chemical resistance, TiN is not adapted for being micro or nanostructured using standard etching process (Reactive Ion Etching for example).…”

A Platform for Complementary Metal‐Oxide‐Semiconductor Compatible Plasmonics: High Plasmonic Quality Titanium Nitride Thin Films on Si (001) with a MgO Interlayer

“…[15][16][17][18] In the area of plasmonics, TiN-based waveguides, [19] gyroidal metamaterials, [20] nanohole metasurfaces, [21] nanoantennas, [22][23][24] and use of TiN nanoparticles for solar energy conversion [25,26] and biomedicine [27] have been reported.However, the majority of the demonstrations of TiN's device potential in plasmonics have been on sapphire and bulk MgO substrates featured by their small lattice mismatch with TiN, enabling the best-performing plasmonic films. [24,[28][29][30][31][32][33] Even then, high deposition temperatures (not congruent with CMOS processes) were usually used to ensure the high structural quality of the TiN films. For example, using reactive sputtering and at a substrate temperature of 650 C, a peak plasmonic figure of merit (FOM ¼ Àε 0 /ε 00 ) of %4.5 has been demonstrated for TiN films on a bulk MgO substrate.…”

Etchless Fabrication of High‐Quality Refractory Titanium Nitride Nanostructures

“…TiN is usually grown in industrial scale by reactive MS, [ 11,45,47–51 ] while alternative techniques include pulsed laser deposition (PLD) from a TiN target, [ 52–54 ] reactive PLD from a Ti target in N 2 ambient, [ 55 ] dual ion beam sputtering (DIBS), [ 56 ] ion beam‐assisted evaporation (IBAE), [ 57,58 ] plasma‐assisted molecular beam epitaxy (MBE) [ 59–62 ] (note that IBAE and MBE are similar equipment‐wise and pressure‐wise), and atomic layer deposition (ALD). [ 63–66 ]…”

“…With the major exception of PLD from a TiN target, the combination of all the other aforementioned techniques with NSL for the formation of well‐defined islands is a challenge due to the inherent limitations regarding the shadow effects through the nanosphere mask. DIBS, IBAE, and MBE have usually working pressure of the order of 10 −4 mbar, set by the operation of the N 2 plasma sources, [ 56–62 ] but the main obstacle for their implementation in combination with NSL is the different angle of incidence of the Ti and N + species that originate from different sources. ALD by its own conception is designed to achieve conformal growth and to eliminate any shadow effects, making it inherently incompatible with NSL.…”