Substrate-insensitive atomic layer deposition of plasmonic titanium nitride films

Abstract

The plasmonic properties of titanium nitride (TiN) films depend on the type of substrate when using typical deposition methods such as sputtering. Here we show atomic layer deposition (ALD) of TiN films with very weak dependence of plasmonic properties on the substrate, which also suggests the prediction and evaluation of plasmonic performance of TiN nanostructures on arbitrary substrates under a given deposition condition. Our results also observe that substrates with more nitrogen-terminated (N-terminated) surfaces will have significant impact on the deposition rate as well as the film plasmonic properties. We further illustrate that the plasmonic properties of ALD TiN films can be tailored by simply adjusting the deposition and/or post-deposition annealing temperatures. Such characteristics and the capability of conformal coating make ALD TiN films on templates ideal for applications that require the fabrication of complex 3D plasmonic nanostructures.

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

“…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. That the plasmon wavelength is red-shifted for TiN on Si compared to the plasmon wavelength of TiN on MgO is likely due to lattice mismatch between silicon and TiN [9]. The trends observed for ε 1 and ε 2 , post-hydrogen treatment, are similar to the ones observed before, and can be explained in a similar manner as above.…”

“…The hydrogen plasma treated TiN (blue) has a plasmon resonance of 554 nm, a 59 nm blue-shift compared to the as-prepared sample. For comparison, it has previously been shown that the plasmon resonance of sputtered TiN films can be been blue shifted by 45 nm after annealing at 600 • C and 71 nm at temperatures of 700 • C [4] Previous ALD syntheses have demonstrated plasmon wavelength blue shifts of 52 nm after post-deposition annealing at 600 • C [9], and 175 nm after post-deposition annealing at 900 • C [3]. The effect of a post deposition hydrogen plasma on the plasmon wavelength can be similar to that of a high temperature anneal, where an increase in the carrier density results in a decrease in ε 1 and, thus, a blue-shift in the plasmon resonance [12].…”

“…TiN's compatibility with silicon is another advantage of alternative plasmonic materials over gold or silver. However, unlike those traditional plasmonic metals, TiN has been demonstrated to have substrate-dependent optical properties and, therefore, it cannot be assumed that the optical properties of TiN on one substrate will be identical to another [8,9,34]. Figure 5 shows the as-prepared TiN (black) has plasmonic character on Si <100> for near 10 nm TiN.…”

“…In addition, when compared to gold, TiN's plasmonic resonance is located within a similar range, but the resonance can be over a broad wavelength region, which is beneficial for a number of applications [8]. However, high temperatures, either in the form of higher deposition temperatures or post-deposition annealing, is required to achieve metallic TiN, especially with plasmon resonances near 500 nm [4,8,9].…”

“…Atomic layer deposition has been explored as a powerful method to overcome these setbacks. It has been shown that thermal ALD performed at temperatures from 450 to 600 • C is less sensitive to substrates than sputtering [9]. Xie et al [13] produced metallic TiN with a growth rate of 0.0178 nm/cycle and resistivity values as low as 300 µΩ cm utilizing titanium (IV) chloride and ammonia precursors.…”