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Plasmonic Titanium Nitride via Atomic Layer Deposition: A Low-Temperature Route

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 T_S > 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 (|ε^'/ε^''|) of 2.8 and resistivity of 31 μΩ-cm. These TiN thin films fabricated with subwavelength apertures were shown to exhibit extraordinary transmission.