Crystal Orientation-Dependent Oxidation of Epitaxial TiN Films with Tunable Plasmonics

Abstract

Titanium nitride (TiN) is a paradigm of refractory transition metal nitrides with great potential in vast applications. Generally, the plasmonic performance of TiN can be tuned by oxidation, which was thought to be only temperature-, oxygen partial pressure-, and timedependent. Regarding the role of crystallographic orientation in the oxidation and resultant optical properties of TiN films, little is known thus far. Here we reveal that both the oxidation resistance behavior and the plasmonic performance of epitaxial TiN films follow the order of (001) < (110) < (111). The effects of crystallographic orientation on the lattice constants, optical properties, and oxidation levels of epitaxial TiN films have been systematically studied by combined high-resolution X-ray diffraction, spectroscopic ellipsometry, X-ray absorption spectroscopy, and X-ray photoemission spectroscopy. To further understand the role of crystallographic orientation in the initial oxidation process of TiN films, density-functionaltheory calculations are carried out, indicating the energy cost of oxidation is (001) < (110) < (111), consistent with the experiments. The superior endurance of the (111) orientation against mild oxidation can largely alleviate the previously stringent technical requirements for the growth of TiN films with high plasmonic performance. The crystallographic orientation can also offer an effective controlling parameter to design TiN-based plasmonic devices with desired peculiarity, e.g., superior chemical stability against mild oxidation or large optical tunability upon oxidation.

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

“…Successful implementation of the titanium nitride as a plasmonic component in photonic devices has been demonstrated on the example of hyperbolic metamaterials working in the visible and infrared ranges [9,10], high-temperature-stable and irradiation-resistant broadband absorber [11], nanoantennas, or other nanostructures able to increase optical response [12][13][14][15][16][17], SERS (Surface-Enhanced Raman Spectroscopy spectroscopy) substrate [18], and remote optical temperature sensor [19]. Apart from applications, the current literature addresses issues related to optimizing the plasmonic properties [20][21][22][23][24][25][26] and the stability of the thin films [26][27][28]. Some quite modern reviews are also available [29,30].…”

Optimized Titanium Nitride Epitaxial Film for Refractory Plasmonics and Solar Energy Harvesting

“…In comparison to (001) and ( 110) orientations, a recent study has demonstrated that the (111)-oriented TiN is more resistant to oxidation, even under a high oxygen partial pressure at 800 °C. 42 To compare with the oxygen-free stoichiometric film grown by MBE, a sputtered (111)-oriented TiN epitaxial film is also prepared by reactive sputtering on c-plane sapphire, and the same metasurface structure is used for a direct comparison. As a simple inspection approach, the absence or presence of oxygen contamination can be judged by the film color and carrier concentration.…”

“…As a simple inspection approach, the absence or presence of oxygen contamination can be judged by the film color and carrier concentration. 30,42 The MBE TiN film exhibits a brilliant golden color, as shown in Figure 1a, and has a free electron concentration as high as 9 × 10 22 cm −3 . 30 Furthermore, ex situ XRD measurements (Figure 1b) reveal that the full width half maxima (FWHM) of the MBE and sputtered TiN(111) peaks are 0.25°and 0.55°, respectively.…”

“…For most of the plasmonic applications demonstrated so far, TiN films are deposited by reactive sputtering or chemical vapor deposition, which is not performed under the preferred ultrahigh vacuum conditions. Therefore, oxygen contamination is a major issue, − which could cause degradation of film properties, such as electrical resistivity, optical response, and thermal stability. In this work, we show that epitaxial growth of the oxidation-resistant TiN(111) film on sapphire by nitrogen-plasma-assisted molecular beam epitaxy (MBE) provides an optimized approach for refractory plasmonics requiring excellent plasmonic properties, as well as high thermal and chemical stabilities.…”

Coherent epitaxy of trilayer nickelate (Nd0.8Sr0.2)4Ni3O10 films by high-pressure magnetron sputtering

“…• C for 8 h and reground for 6 h. Then the powders were pressed into a 2-inch target with 30 MPa and annealed at 1300 • C for 2 h. The high-quality NSNO 4310 thin films (∼ 20 nm) were synthesized by high-pressure radio frequency (RF) magnetron sputtering (home-made) with a 2-inch target and the O 2 (purity of 99.999%) reactive gas [43,44]. Before growth, the base vacuum pressure was ∼ 3 ×10 −8 torr.…”