To integrate plasmonic devices into industry, it is essential to develop scalable and CMOS compatible plasmonic materials. In this work, we report high plasmonic quality titanium nitride (TiN) on c-plane sapphire by plasma enhanced atomic layer deposition (PE-ALD). TiN with low losses and high metallicity was achieved at temperatures below 500°C, by exploring the effects of chemisorption time, substrate temperature and plasma exposure time on material properties. Reduction in chemisorption time mitigates premature precursor decomposition at TS > 375°C , and a trade-off between reduced impurity concentration and structural degradation caused by plasma bombardment is achieved for 25s plasma exposure. 85 nm thick TiN films grown at a substrate temperature of 450°C, compatible with CMOS processes, with 0.5s chemisorption time and 25s plasma exposure exhibited a high plasmonic figure of merit (| ′ / ′′ |) of 2.8 and resistivity of 31 μΩ − cm. These TiN thin films fabricated with subwavelength apertures were shown to exhibit extraordinary transmission.

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

Major technological breakthroughs are often driven by advancements in materials research, and optics is no different. Over the last few years, near-zero-index (NZI) materials have triggered significant interest owing to their exceptional tunability of optical properties and enhanced light-matter interaction, leading to several demonstrations of compact, energy-efficient, and dynamic nanophotonic devices. Many of these devices have relied on transparent conducting oxides (TCOs) as a dynamic layer, as these materials exhibit a near-zero-index at telecommunication wavelengths. Among a wide range of techniques employed for the deposition of TCOs, atomic layer deposition (ALD) offers advantages such as conformality, scalability, and low substrate temperature. However, the ALD process often results in films with poor optical quality, due to low doping efficiencies at high (>1020cm−3) doping levels. In this work, we demonstrate a modified ALD process to deposit TCOs, taking Al:ZnO as an example, which results in an increase in doping efficiency from 13% to 54%. Moving away from surface saturation for the dopant (aluminum) precursor, the modified ALD process results in a more uniform distribution of dopants (Al) throughout the film, yielding highly conductive (2.8×10−4 Ω-cm) AZO films with crossover wavelengths as low as 1320nm and 1370nm on sapphire and silicon substrates, respectively.

No abstract

Electromagnetic radiation when coupled to collective oscillations of free electrons, dubbed as plasmonics, makes it possible to manipulate light at dimensions well below the diffraction limit and substantially enhances light–matter interaction. Plasmonics has already enabled many novel technologies with a wide variety of application in chemical and biosensing, medical treatments, nonlinear and quantum optics, metamaterials, optical nanotweezers, nanolasers, solar cells, light‐emitting diodes, and telecommunications. Coating the well‐established semiconductor circuitry with metals, such as Au and Ag, imparts the stack with much coveted plasmonic properties, but the metals suffer from high dissipative losses, limited optical tunability, and poor mechanical, chemical, and thermal stabilities, which render them undesirable. Emerging alternative plasmonic materials, such as TiN and ZnO:Al, overcome these limitations and offer wide tunability of their electrical and optical properties. Among a wide range of techniques used for the preparation of TiN and ZnO:Al thin films, atomic layer deposition (ALD) offers advantages such as conformity, scalability, and low growth temperature, which makes this technique the most suitable for the integration of plasmonics with the complementary metal–oxide–semiconductor (CMOS) electronics. Herein, a brief review of recent advances in ALD‐grown TiN and ZnO:Al thin films as pertained to plasmonic applications is given.