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

Abstract

By coupling photons into collective oscillations of free electrons, plasmonics enables the emergence of novel technologies with the combined capabilities of photonics and miniaturized electronics. [1] In the past few decades, a large variety of plasmonicsbased applications have been demonstrated. These include nanolasers, [2,3] interconnects, [4,5] modulators, [5][6][7][8][9] chemicaland bio-sensors, [10,11] as well as light-emitting diodes and photovoltaic devices where plasmonics is used for efficiency enhancement. [12,13] One of the most attractive materials alternative to noble metals that drive the plasmonics revolution, is titanium nitride (TiN), which has been investigated extensively due to its low-cost, gold-like, and tunable optical properties in the visible and near-infrared range, high thermal and chemical stability, high mechanical hardness, and bio-and complementary metaloxide-semiconductor (CMOS) compatibilities. [14] TiN has been widely used as a gate electrode in various CMOS devices. [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. [24] Single-crystalline, highly metallic TiN films with an electron concentration of 9.2 Â 10 22 cm À3 and a peak plasmonic FOM as high as %5.8 have been achieved on c-sapphire substrates by plasma-assisted molecularbeam epitaxy (PA-MBE) at a substrate temperature of 1000 C. [28] However, realizing the true potential of TiN-based plasmonics through integration with the CMOS electronics necessitates

Titanium Nitride as a Plasmonic Material from Near-Ultraviolet to Very-Long-Wavelength Infrared Range

“…Optical measurements performed four months after the first ones do not reveal any significant changes in the optical properties, so the samples are quite stable. The plasmonic figure of merit value expressed as FoM = |ε 1 |/ε 2 , in the best case of the stoichiometric sample, reaches the value of 1.86, which is an excellent result for a sputtering process conducted at room temperature [56].…”

“…Materials 2021, 14, x FOR PEER REVIEW 7 of 16 the value of 1.86, which is an excellent result for a sputtering process conducted at room temperature [56]. Formally, the dielectric function ε in the range of 193 nm to 1.69 µm can be described analytically as a sum of one Drude component and four Lorentz oscillators:…”

High‐Quality Plasmonic Materials TiN and ZnO:Al by Atomic Layer Deposition

“…As noted, the TiN films in this work were grown under the same PE-ALD conditions, so similar metallicity was attributed to similar stoichiometry and oxygen impurity concentration among the samples grown on different substrates. In contrast, the optical losses for TiN on MgO/Si were significantly lower as compared with those for TiN on Si due to the improvement in crystallinity [47] Copyright 2021, The Authors, published by Wiley-VCH.…”

“…c) FoM for TiN films deposited on various substrates (MgO, sapphire, Si, SiO 2 , and MgO/Si stack) by sputtering, [ 37,44–46 ] pulsed laser deposition (PLD), [ 43 ] and ALD. [ 47 ] a–c) Adapted with permission. [ 37 ] Copyright 2019, American Chemical Society.…”

“…Very recently, Ding et al [ 47,74 ] addressed the insufficient optical quality of TiN films on Si substrates by inserting a thin (10 nm) MgO interlayer. The MgO layers were grown on Si (001) substrates by plasma‐assisted MBE at 680 °C.…”