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

^{1}

^{2}

^{3}

^{4}

^{5}

^{*}

## Abstract

**:**

_{x}films sputtered on silicon at room temperature can exhibit plasmonic properties continuously from 400 nm up to 30 μm. The films’ composition, expressed as nitrogen to titanium ratio x and determined in the Secondary Ion Mass Spectroscopy (SIMS) experiment to be in the range of 0.84 to 1.21, is essential for optimizing the plasmonic properties. In the visible range, the dielectric function renders the interband optical transitions. For wavelengths longer than 800 nm, the optical properties of TiN

_{x}are well described by the Drude model modified by an additional Lorentz term, which has to be included for part of the samples. The ab initio calculations support the experimental results both in the visible and infra-red ranges; particularly, the existence of a very low energy optical transition is predicted. Some other minor features in the dielectric function observed for the longest wavelengths are suspected to be of phonon origin.

## 1. Introduction

## 2. Materials, Methods and Models

#### 2.1. Magnetron Sputtering

_{x}samples was controlled by the ratio of nitrogen flux to argon flux while keeping the total flux approximately constant. Provided power, deposition time, pressure, and other details of the deposition process, except gas fluxes, were kept constant for all the samples. For our experiments, we fabricated three of the same series of seven samples each. A picture of one of the series is shown in Figure 1a. The first sample is the most nitrogen-rich, the fifth is almost stoichiometric, and the last is the most nitrogen-deficient.

#### 2.2. SIMS

_{x}samples was determined from the SIMS experiment using IMS SC Ultra instrument (CAMECA, Gennevilliers Cedex, France) under ultra-high vacuum, typically 4 × 10

^{−10}mbar. Cs+ primary beam was rastered over 250 × 250 µm

^{2}, and the analysis area was limited to 200 × 200 µm

^{2}. The intensity of the primary beam was 40 nA, and the impact energy was 7 keV. Positive ions detection mode was used in the experiments, and thus all species were measured as CsX+ cluster ions. To determine the composition of TiN

_{x}CsN+/CsTi+, the signals ratio was calibrated with a reference sample (stoichiometric TiN). Twenty independent measurements were performed for each sample. The result of the measurement is the mean value of all measurements, whereas the uncertainty is the standard deviation value.

#### 2.3. XRD

_{i}= 0.4°. Data were collected at room temperature in the 2θ angle range of 25° to 85°, in steps of 0.0263° with an effective scan time of 300 s per step. The incidence angle has been determined experimentally in a series of reference measurements with a varying value of the incidence angle (Supplementary Material, Figure S1).

#### 2.4. Raman Spectroscopy

_{x}samples were performed under normal conditions using an InVia Reflex Raman spectrometer (Renishaw, New Mills, UK), in a backscatter configuration. A diode-pumped laser (DPSS) with a 532 nm line was applied as excitation. Complementary measurements with a 785 nm diode-type laser line excluded resonance effects. Temperature investigations made using a Linkam DSC600 temperature cell cooled with liquid nitrogen under an argon atmosphere proved the structural stability of all samples in the temperature range of 80 K to 420 K.

#### 2.5. Optical Properties and Models

_{x}films. We are aware that we are neglecting the surface roughness or oxidation [29]. Still, on the other hand, such an approach allows us to more freely analyze the ε(λ) function, observe minor features, and more consciously interpret the deviation of the assumed dispersion model from experimental data.

_{x}samples depends on the spectral range. In the first spectral range of 193 nm to 1.7 μm, we assumed that the optical model for all TiN

_{x}samples deposited on a silicon substrate is just semi-infinite TiN

_{x}film. It is because, for the expected values of ε and thicknesses determined from Scanning Electron Microscopy (SEM) cross-section images, all samples are opaque. Formally, we used the following identities:

_{x}films of finite thickness on a silicon semi-infinite substrate. The silicon substrate is treated as semi-infinite because it is polished on one side, and the second side is very rough, which cancels all the reflections. Formally, we change the expressions for ${r}_{\mathrm{s},\mathrm{p}}$ to be:

_{x}film thickness value, and ${n}_{\mathrm{Si}}$ is the silicon substrate refractive index value calculated from the measured $\Psi $ and $\Delta $ values using Equation (1).

#### 2.6. Ab Initio Calculations

^{−5}eV/Å. Phonon spectrum was calculated using the Parlinski-Li-Kawazoe method supercell approach with the finite displacement method [46] as implemented in the Phonopy code [47]. Optical properties were calculated on the Random-Phase Approximation (RPA) level [48] as implemented in the VASP code [49].

## 3. Results

#### 3.1. Structural Properties

_{1.21±0.02}for sample 1 to TiN

_{0.84±0.03}for sample 7, with sample 5 being almost stoichiometric. Hence, there are four samples with excess nitrogen content and only two with deficient nitrogen content. This situation results from the different stability of the sputtering process for samples characterized by excess and deficient nitrogen content. A precise composition control is easily achievable for the first class of samples in our experimental setup since the sputtering process is stable. In contrast, the sputtering process is very susceptible to the process parameters for the samples with nitrogen deficiency, and thus, it is not easy to achieve the exact desired composition.

_{x}composition with its optical properties, namely the wavelength at which the real part of the dielectric function equals zero λ@ε

_{1}= 0. It is a popular treatment for plasmonic TiN

_{x}. We found a linear dependence, as shown in Figure 1c. This result fits well with the trends reported in the literature [52,53]. Formally:

_{0}is demanding.

#### 3.2. Optical Properties in the UV-VIS Range

#### 3.3. Optical Properties in the Infrared Range

_{x}samples in the visible range, data in Table 3 are much more reliable and also pretty unique. Pictures illustrating experimental and simulated values of the dielectric function in the considered range are shown in Supporting Information Figures S32–S38.

#### 3.4. Ab Initio Calculations

_{0}W

_{0}correction (one-shot GW correction) to quasiparticle energies significantly shifts the band positions, especially those below the Fermi level. The most striking effect is decreased separation energy between the “valence-like” and “conduction-like” bands at the center of the Brillouin zone, whereas the bands’ shapes seem less affected. In Figure 3b, one can find the optical properties, namely the imaginary part of the dielectric function, which were calculated using random phase approximation (RPA). The PBE + RPA results seem to agree with previous work [62] and our experimental dielectric function for the stoichiometric sample (please see the peak position in Figure 3b at 1.9 eV, 3.7 eV, 5.2 eV, and 6.4 eV, and values in Table 2). The main difference between the simulated and experimental dielectric function is that in the experimental curve, the peaks are more blurred compared to quite distinct peaks in the simulated curve. A possible explanation is that our sample is polycrystalline; thus, experimental results are obtained from a set of many grains. Suppose the optical properties (i.e., parameters of the Lorentz oscillators describing each grain) differ within the set of grains. In that case, the resulting optical properties will be a convolution of all particular optical properties with weight proportional to their contributions. As a consequence, all the peaks will blur.

#### 3.5. Raman Measurements

_{x}, despite some differences from published reports [73,74,75,76,77] in peak number and positions, which, however, can be very technology-dependent. The main features of the Raman spectra are peaks related to both acoustic and optical phonons, both first and second-order, which for the stoichiometric sample are located at 200 cm

^{−1}, 255 cm

^{−1}, 304 cm

^{−1}, 407 cm

^{−1}, 540 cm

^{−1}, 551 cm

^{−1}, 804 cm

^{−1}, and 1090 cm

^{−1}. We note that, typically, only optical phonons from the center of the Brillouin zone are observed in Raman spectra. The occurrence of the first-order acoustic phonons means that the selection rules for the Raman scattering process are violated, which can happen, for example, in the presence of structural defects, which also include the grain boundaries. On the other hand, the first-order acoustic modes are also observed in epitaxial layers characterized by the low defect concentration [75], suggesting that the violation of the typical Raman selection rules can be an intrinsic property of titanium nitride. Contrary to other authors, we do not dare to assign observed peaks to corresponding phonons since our experiments and theoretical calculations do not provide enough information to make reliable assignments. To show the complexity of this task, we use the results of our ab initio calculations, as shown in Figure 4b. We note that our calculations agree with the inelastic phonon scattering experiment [78] and previously reported calculations [79]. Considering two peaks located at 540 cm

^{−1}and 551 cm

^{−1}, one can suspect that these peaks are optical modes that reflect the phonon density of states at the Γ-X and Γ-K direction related to the LO branch. However, our samples are polycrystalline and sputtered on a mismatched substrate. Thus, our samples can be affected by unidentified stress, which is known to seriously modify the phonons’ properties [77], e.g., by stiffening the lattice vibrations. Consequently, it may turn out that the 540 cm

^{−1}and 551 cm

^{−1}peaks are related to the TO phonon branch, which is shifted to higher energies due to stress. Moreover, because the second-order features are observed in the Raman spectra (undoubtedly, the peaks at 804 cm

^{−1}and 1090 cm

^{−1}are second-order features), it is possible that the second-order acoustic modes also contribute to the Raman spectra in the range of 500 cm

^{−1}to 600 cm

^{−1}, which makes the mode identification even more challenging.

_{x}samples. The second conclusion is that the Raman spectra are rich. Assuming that light absorption by phonons in the infrared range will be at least somehow similar to inelastic light scattering by phonons in the visible range, one can expect that dielectric function can be affected by phonons, up to the wavelength of 8 μm. In Figure 4a, an additional scale at the top of the plot expresses the phonon energy in the wavelength units to help compare Figure 2 with Figure 4. Translating the energy range in which the density of optical phonons is non-zero, i.e., approximately from 485 cm

^{−1}to 566 cm

^{−1}according to Figure 4b, into the wavelength range, we obtain approximately the range of 17.5 μm to 20.4 μm. Particularly, the Raman peak at 551 cm

^{−1}can be related to the feature in the real part of the dielectric function at 18 μm. Other features observed in ${\epsilon}_{1}$, if of phonon origin, should arise from a multi-phonon absorption process.

## 4. Conclusions

_{x}films can exhibit plasmonic properties continuously from 400 nm up to 30 μm for stoichiometry in the range of x = 1.21 ± 0.02 to x = 0.84 ± 0.03, and we provide reliable parametrized analytical models valid in the range of 800 nm to 20 μm. For wavelengths longer than 800 nm, we found that the optical properties of TiN

_{x}generally follow the Drude model. However, we identified an apparent deviation from the Drude model for part of the samples. An additional Lorentz term can describe this deviation, but its origin is still unknown at the moment of writing this publication. Since it is the first report on the dielectric function for such long wavelengths, we could not support our consideration with the literature, limiting ourselves to providing possible explanations. The first pending question is whether the observed deviation is a technology-specific issue, such as the grain boundaries’ influence limiting the electron movement or material property. If it is a material property, the next question is if the considered deviation is related to the band structure, like the parallel-band effect, or maybe some corrections to the Drude model are required, similar to those applied for electrically conducting polymers [80].

## Supplementary Materials

_{i}> 1.0°) show diffraction peaks from the Si substrate. The highest signal-to-noise ratio is observed for α

_{i}= 0.4°; Figure S2. SEM image of a cross-section of sample number 1; Figure S3. SEM image of a cross-section of sample number 2; Figure S4. SEM image of a cross-section of sample number 3; Figure S5. SEM image of a cross-section of sample number 4; Figure S6. SEM image of a cross-section of sample number 5; Figure S7. SEM image of a cross-section of sample number 6; Figure S8. SEM image of a cross-section of sample number 7; Figure S9. SEM image of a surface of sample number 1; Figure S10. SEM image of sample number 2; Figure S11. SEM image of sample number 3; Figure S12. SEM image of sample number 4; Figure S13. SEM image of sample number 5; Figure S14. SEM image of sample number 6; Figure S15. SEM image of sample number 7; Figure S16. AFM image of sample number 1; Figure S17. AFM image of sample number 2; Figure S18. AFM image of sample number 3; Figure S19. AFM image of sample number 4; Figure S20. AFM image of sample number 5; Figure S21. AFM image of sample number 6; Figure S22. AFM image of sample number 7; Figure S23. Ellipsometric parameters Ψ and Δ as a function of wavelength in two spectral ranges for sample number 1; Figure S24. Ellipsometric parameters Ψ and Δ as a function of wavelength in two spectral ranges for sample number 2; Figure S25. Ellipsometric parameters Ψ and Δ as a function of wavelength in two spectral ranges for sample number 3; Figure S26. Ellipsometric parameters Ψ and Δ as a function of wavelength in two spectral ranges for sample number 4; Figure S27. Ellipsometric parameters Ψ and Δ as a function of wavelength in two spectral ranges for sample number 5; Figure S28. Ellipsometric parameters Ψ and Δ as a function of wavelength in two spectral ranges for sample number 6; Figure S29. Ellipsometric parameters Ψ and Δ as a function of wavelength in two spectral ranges for sample number 7; Figure S30. Ellipsometric parameters Ψ and Δ as a function of wavelength in two spectral ranges for Si substrate; Figure S31. Extracted and simulated dielectric function in the low-energy range for freshly evaporated 300 nm thick Ag film on glass; Figure S32. Extracted and simulated dielectric function in the low-energy range for sample number 1; Figure S33. Extracted and simulated dielectric function in the low-energy range for sample number 2; Figure S34. Extracted and simulated dielectric function in the low-energy range for sample number 3; Figure S35. Extracted and simulated dielectric function in the low-energy range for sample number 4; Figure S36. Extracted and simulated dielectric function in the low-energy range for sample number 5; Figure S37. Extracted and simulated dielectric function in the low-energy range for sample number 6; Figure S38. Extracted and simulated dielectric function in the low-energy range for sample number 7.

## Author Contributions

## Funding

## Institutional Review Board Statement

## Informed Consent Statement

## Data Availability Statement

## Conflicts of Interest

## Abbreviations

AFM | Atomic Force Microscopy |

CMOS | Complementary Metal-Oxide-Semiconductor |

DFT | Density Functional Theory |

EDS | Energy-dispersive X-ray spectroscopy |

FTIR | Fourier transform infrared (spectroscopy) |

GGA | Generalized Gradient Approximation |

GIXRD | Grazing Incidence X-ray Diffraction |

LO | Longitudinal Optical (phonon) |

PBE | Perdew-Burke-Ernzerhof (parametrization) |

RMS | Root-Mean-Square |

RPA | Random-Phase Approximation |

SEM | Scanning Electron Microscopy |

SERS | Surface-Enhanced Raman Spectroscopy |

SIMS | Secondary Ion Mass Spectroscopy |

TO | Transverse Optical (phonon) |

UV | Ultra-violet (spectral range) |

VASE | Variable-Angle Spectroscopic Ellipsometry |

VIS | Visible (spectral range) |

## References

- Rebenne, H.E.; Bhat, D.G. Review of CVD TiN Coatings for Wear-Resistant Applications: Deposition Processes, Properties and Performance. Surf. Coat. Technol.
**1994**, 63, 1–13. [Google Scholar] [CrossRef] - Nose, M.; Zhou, M.; Honbo, E.; Yokota, M.; Saji, S. Colorimetric Properties of ZrN and TiN Coatings Prepared by DC Reactive Sputtering. Surf. Coat. Technol.
**2001**, 142–144, 211–217. [Google Scholar] [CrossRef] - Yokoyama, N.; Hinode, K.; Homma, Y. LPCVD Titanium Nitride for ULSIs. J. Electrochem. Soc.
**1991**, 138, 190–195. [Google Scholar] [CrossRef] - Dauskardt, R.H.; Lane, M.; Ma, Q.; Krishna, N. Adhesion and Debonding of Multi-Layer Thin film Structures. Eng. Fract. Mech.
**1998**, 61, 141–162. [Google Scholar] - Lemme, M.C.; Efavi, J.K.; Mollenhauer, T.; Schmidt, M.; Gottlob, H.D.B.; Wahlbrink, T.; Kurz, H. Nanoscale TiN Metal Gate Technology for CMOS Integration. Microelectron. Eng.
**2006**, 83, 1551–1554. [Google Scholar] [CrossRef] - Naik, G.V.; Kim, J.; Boltasseva, A. Oxides and Nitrides as Alternative Plasmonic Materials in the Optical Range [Invited]. Opt. Mater. Express OME
**2011**, 1, 1090–1099. [Google Scholar] [CrossRef] [Green Version] - Naik, G.V.; Schroeder, J.L.; Ni, X.; Kildishev, A.V.; Sands, T.D.; Boltasseva, A. Titanium Nitride as a Plasmonic Material for Visible and Near-Infrared Wavelengths. Opt. Mater. Express
**2012**, 2, 478. [Google Scholar] [CrossRef] [Green Version] - Naik, G.V.; Shalaev, V.M.; Boltasseva, A. Alternative Plasmonic Materials: Beyond Gold and Silver. Adv. Mater.
**2013**, 25, 3264–3294. [Google Scholar] - Naik, G.V.; Saha, B.; Liu, J.; Saber, S.M.; Stach, E.A.; Irudayaraj, J.M.K.; Sands, T.D.; Shalaev, V.M.; Boltasseva, A. Epitaxial Superlattices with Titanium Nitride as a Plasmonic Component for Optical Hyperbolic Metamaterials. Proc. Natl. Acad. Sci. USA
**2014**, 111, 7546–7551. [Google Scholar] [CrossRef] [Green Version] - Huang, J.; Zhang, D.; Wang, H. Epitaxial TiN/MgO Multilayers with Ultrathin TiN and MgO Layers as Hyperbolic Metamaterials in Visible Region. Mater. Today Phys.
**2021**, 16, 100316. [Google Scholar] [CrossRef] - Li, W.; Guler, U.; Kinsey, N.; Naik, G.V.; Boltasseva, A.; Guan, J.; Shalaev, V.M.; Kildishev, A.V. Refractory Plasmonics with Titanium Nitride: Broadband Metamaterial Absorber. Adv. Mater.
**2014**, 26, 7959–7965. [Google Scholar] - Gui, L.; Bagheri, S.; Strohfeldt, N.; Hentschel, M.; Zgrabik, C.M.; Metzger, B.; Linnenbank, H.; Hu, E.L.; Giessen, H. Nonlinear Refractory Plasmonics with Titanium Nitride Nanoantennas. Nano Lett.
**2016**, 16, 5708–5713. [Google Scholar] - Briggs, J.A.; Naik, G.V.; Petach, T.A.; Baum, B.K.; Goldhaber-Gordon, D.; Dionne, J.A. Fully CMOS-Compatible Titanium Nitride Nanoantennas. Appl. Phys. Lett.
**2016**, 108, 051110. [Google Scholar] [CrossRef] - Kharintsev, S.S.; Kharitonov, A.V.; Saikin, S.K.; Alekseev, A.M.; Kazarian, S.G. Nonlinear Raman Effects Enhanced by Surface Plasmon Excitation in Planar Refractory Nanoantennas. Nano Lett.
**2017**, 17, 5533–5539. [Google Scholar] [CrossRef] - Wen, X.; Li, G.; Gu, C.; Zhao, J.; Wang, S.; Jiang, C.; Palomba, S.; Martijn de Sterke, C.; Xiong, Q. Doubly Enhanced Second Harmonic Generation through Structural and Epsilon-near-Zero Resonances in TiN Nanostructures. ACS Photonics
**2018**, 5, 2087–2093. [Google Scholar] [CrossRef] - Gadalla, M.N.; Greenspon, A.S.; Tamagnone, M.; Capasso, F.; Hu, E.L. Excitation of Strong Localized Surface Plasmon Resonances in Highly Metallic Titanium Nitride Nano-Antennas for Stable Performance at Elevated Temperatures. ACS Appl. Nano Mater.
**2019**, 2, 3444–3452. [Google Scholar] [CrossRef] - Gadalla, M.N.; Chaudhary, K.; Zgrabik, C.M.; Capasso, F.; Hu, E.L. Imaging of Surface Plasmon Polaritons in Low-Loss Highly Metallic Titanium Nitride Thin Films in Visible and Infrared Regimes. Opt. Express
**2020**, 28, 14536. [Google Scholar] [CrossRef] - Kaisar, N.; Huang, Y.-T.; Jou, S.; Kuo, H.-F.; Huang, B.-R.; Chen, C.-C.; Hsieh, Y.-F.; Chung, Y.-C. Surface-Enhanced Raman Scattering Substrates of Flat and Wrinkly Titanium Nitride Thin Films by Sputter Deposition. Surf. Coat. Technol.
**2018**, 337, 434–438. [Google Scholar] [CrossRef] - Chaudhuri, K.; Guler, U.; Azzam, S.I.; Reddy, H.; Saha, S.; Marinero, E.E.; Kildishev, A.V.; Shalaev, V.M.; Boltasseva, A. Remote Sensing of High Temperatures with Refractory, Direct-Contact Optical Metacavity. ACS Photonics
**2020**, 7, 472–479. [Google Scholar] [CrossRef] - Zgrabik, C.M.; Hu, E.L. Optimization of Sputtered Titanium Nitride as a Tunable Metal for Plasmonic Applications. Opt. Mater. Express
**2015**, 5, 2786. [Google Scholar] [CrossRef] [Green Version] - Guo, W.-P.; Mishra, R.; Cheng, C.-W.; Wu, B.-H.; Chen, L.-J.; Lin, M.-T.; Gwo, S. Titanium Nitride Epitaxial Films as a Plasmonic Material Platform: Alternative to Gold. ACS Photonics
**2019**, 6, 1848–1854. [Google Scholar] [CrossRef] - Chang, C.-C.; Nogan, J.; Yang, Z.-P.; Kort-Kamp, W.J.M.; Ross, W.; Luk, T.S.; Dalvit, D.A.R.; Azad, A.K.; Chen, H.-T. Highly Plasmonic Titanium Nitride by Room-Temperature Sputtering. Sci. Rep.
**2019**, 9, 15287. [Google Scholar] [CrossRef] [Green Version] - Fomra, D.; Secondo, R.; Ding, K.; Avrutin, V.; Izyumskaya, N.; Özgür, Ü.; Kinsey, N. Plasmonic Titanium Nitride via Atomic Layer Deposition: A Low-Temperature Route. J. Appl. Phys.
**2020**, 127, 103101. [Google Scholar] [CrossRef] - Chen, L.; Ran, Y.; Jiang, Z.; Li, Y.; Wang, Z. Structural, Compositional, and Plasmonic Characteristics of Ti–Zr Ternary Nitride Thin Films Tuned by the Nitrogen Flow Ratio in Magnetron Sputtering. Nanomaterials
**2020**, 10, 829. [Google Scholar] [CrossRef] - Maurya, K.C.; Shalaev, V.M.; Boltasseva, A.; Saha, B. Reduced Optical Losses in Refractory Plasmonic Titanium Nitride Thin Films Deposited with Molecular Beam Epitaxy. Opt. Mater. Express
**2020**, 10, 2679. [Google Scholar] [CrossRef] - Zhang, R.; Ma, Q.-Y.; Liu, H.; Sun, T.-Y.; Bi, J.; Song, Y.; Peng, S.; Liang, L.; Gao, J.; Cao, H.; et al. Crystal Orientation-Dependent Oxidation of Epitaxial TiN Films with Tunable Plasmonics. ACS Photonics
**2021**, 8, 847–856. [Google Scholar] [CrossRef] - Shah, D.; Reddy, H.; Kinsey, N.; Shalaev, V.M.; Boltasseva, A. Optical Properties of Plasmonic Ultrathin TiN Films. Adv. Opt. Mater.
**2017**, 5, 1700065. [Google Scholar] [CrossRef] - Shah, D.; Catellani, A.; Reddy, H.; Kinsey, N.; Shalaev, V.; Boltasseva, A.; Calzolari, A. Controlling the Plasmonic Properties of Ultrathin TiN Films at the Atomic Level. ACS Photonics
**2018**, 5, 2816–2824. [Google Scholar] [CrossRef] [Green Version] - Patsalas, P.; Kalfagiannis, N.; Kassavetis, S. Optical Properties and Plasmonic Performance of Titanium Nitride. Materials
**2015**, 8, 3128–3154. [Google Scholar] [CrossRef] [Green Version] - Patsalas, P.; Kalfagiannis, N.; Kassavetis, S.; Abadias, G.; Bellas, D.V.; Lekka, C.; Lidorikis, E. Conductive Nitrides: Growth Principles, Optical and Electronic Properties, and Their Perspectives in Photonics and Plasmonics. Mater. Sci. Eng. R Rep.
**2018**, 123, 1–55. [Google Scholar] [CrossRef] - Edlou, S.M.; Simons, J.C.; Al-Jumaily, G.A.; Raouf, N.A. Optical and Electrical Properties of Reactively Sputtered TiN, ZrN, and HfN Thin Films. In Optical Thin Films IV: New Developments; International Society for Optics and Photonics: Bellingham, WA, USA, 1994; Volume 2262, pp. 96–106. [Google Scholar]
- Adachi, S.; Takahashi, M. Optical Properties of TiN Films Deposited by Direct Current Reactive Sputtering. J. Appl. Phys.
**2000**, 87, 1264–1269. [Google Scholar] [CrossRef] - Patsalas, P.; Logothetidis, S. Optical, Electronic, and Transport Properties of Nanocrystalline Titanium Nitride Thin Films. J. Appl. Phys.
**2001**, 90, 4725–4734. [Google Scholar] [CrossRef] - Karlsson, B.; Shimshock, R.P.; Seraphin, B.O.; Haygarth, J.C. Optical Properties of CVD-Coated TiN, ZrN and HfN. Sol. Energy Mater.
**1983**, 7, 401–411. [Google Scholar] [CrossRef] - Cinali, M.B.; Coşkun, Ö.D. Improved Infrared Emissivity of Diamond-like Carbon Sandwich Structure with Titanium Nitride Metallic Interlayer. Sol. Energy
**2020**, 204, 644–653. [Google Scholar] [CrossRef] - Ogawa, S.; Okada, K.; Fukushima, N.; Kimata, M. Wavelength Selective Uncooled Infrared Sensor by Plasmonics. Appl. Phys. Lett.
**2012**, 100, 021111. [Google Scholar] [CrossRef] - De Luca, A.; Ali, S.Z.; Hopper, R.H.; Boual, S.; Gardner, J.W.; Udrea, F. Filterless non-dispersive infra-red gas detection: A proof of concept. In Proceedings of the 2017 IEEE 30th International Conference on Micro Electro Mechanical Systems (MEMS), Las Vegas, NV, USA, 22–26 January 2017; pp. 1220–1223. [Google Scholar]
- Xing, Y.; Urasinska-Wojcik, B.; Gardner, J.W. Plasmonic enhanced CMOS non-dispersive infrared gas sensor for acetone and ammonia detection. In Proceedings of the 2018 IEEE International Instrumentation and Measurement Technology Conference (I2MTC), Houston, TX, USA, 14–17 May 2018; pp. 1–5. [Google Scholar]
- Kresse, G.; Hafner, J. Ab Initio Molecular Dynamics for Liquid Metals. Phys. Rev. B
**1993**, 47, 558–561. [Google Scholar] [CrossRef] - Kresse, G.; Hafner, J. Ab Initio Molecular-Dynamics Simulation of the Liquid-Metal–Amorphous-Semiconductor Transition in Germanium. Phys. Rev. B
**1994**, 49, 14251–14269. [Google Scholar] [CrossRef] - Kresse, G.; Furthmüller, J. Efficiency of Ab-Initio Total Energy Calculations for Metals and Semiconductors Using a Plane-Wave Basis Set. Comput. Mater. Sci.
**1996**, 6, 15–50. [Google Scholar] [CrossRef] - Kresse, G.; Furthmüller, J. Efficient Iterative Schemes for Ab Initio Total-Energy Calculations Using a Plane-Wave Basis Set. Phys. Rev. B
**1996**, 54, 11169–11186. [Google Scholar] [CrossRef] - Blöchl, P.E. Projector Augmented-Wave Method. Phys. Rev. B
**1994**, 50, 17953–17979. [Google Scholar] [CrossRef] [Green Version] - Kresse, G.; Joubert, D. From Ultrasoft Pseudopotentials to the Projector Augmented-Wave Method. Phys. Rev. B
**1999**, 59, 1758–1775. [Google Scholar] [CrossRef] - Perdew, J.P.; Burke, K.; Ernzerhof, M. Generalized Gradient Approximation Made Simple. Phys. Rev. Lett.
**1996**, 77, 3865–3868. [Google Scholar] [CrossRef] [Green Version] - Parlinski, K.; Li, Z.Q.; Kawazoe, Y. First-Principles Determination of the Soft Mode in Cubic ZrO
_{2}. Phys. Rev. Lett.**1997**, 78, 4063–4066. [Google Scholar] [CrossRef] - Togo, A.; Tanaka, I. First Principles Phonon Calculations in Materials Science. Scr. Mater.
**2015**, 108, 1–5. [Google Scholar] [CrossRef] [Green Version] - Ehrenreich, H.; Cohen, M.H. Self-Consistent Field Approach to the Many-Electron Problem. Phys. Rev.
**1959**, 115, 786–790. [Google Scholar] [CrossRef] - Gajdoš, M.; Hummer, K.; Kresse, G.; Furthmüller, J.; Bechstedt, F. Linear Optical Properties in the Projector-Augmented Wave Methodology. Phys. Rev. B
**2006**, 73, 045112. [Google Scholar] [CrossRef] [Green Version] - Elstner, F.; Ehrlich, A.; Giegengack, H.; Kupfer, H.; Richter, F. Structure and Properties of Titanium Nitride Thin Films Deposited at Low Temperatures Using Direct Current Magnetron Sputtering. J. Vac. Sci. Technol. A Vac. Surf. Film.
**1994**, 12, 476–483. [Google Scholar] [CrossRef] - Mahieu, S.; Ghekiere, P.; Depla, D.; De Gryse, R. Biaxial Alignment in Sputter Deposited Thin Films. Thin Solid Film.
**2006**, 515, 1229–1249. [Google Scholar] [CrossRef] [Green Version] - Bendavid, A.; Martin, P.J.; Netterfield, R.P.; Kinder, T.J. Characterization of the Optical Properties and Composition of TiN
_{x}Thin Films by Spectroscopic Ellipsometry and X-Ray Photoelectron Spectroscopy. Surf. Interface Anal.**1996**, 24, 627–633. [Google Scholar] - Walker, C.G.H.; Matthew, J.A.D.; Anderson, C.A.; Brown, N.M.D. An Estimate of the Electron Effective Mass in Titanium Nitride Using UPS and EELS. Surf. Sci.
**1998**, 412–413, 405–414. [Google Scholar] [CrossRef] - Srivastava, A.; Chauhan, M.; Singh, R.K. Pressure Induced Phase Transitions in Transition Metal Nitrides: Ab Initio Study: Pressure Induced Phase Transitions in Transition Metal Nitrides. Phys. Status Solidi B
**2011**, 248, 2793–2800. [Google Scholar] [CrossRef] - Yu, S.; Zeng, Q.; Oganov, A.R.; Frapper, G.; Zhang, L. Phase Stability, Chemical Bonding and Mechanical Properties of Titanium Nitrides: A First-Principles Study. Phys. Chem. Chem. Phys.
**2015**, 17, 11763–11769. [Google Scholar] [CrossRef] [Green Version] - Ding, K.; Fomra, D.; Kvit, A.V.; Morkoç, H.; Kinsey, N.; Özgür, Ü.; Avrutin, V. A Platform for Complementary Metal-Oxide-Semiconductor Compatible Plasmonics: High Plasmonic Quality Titanium Nitride Thin Films on Si (001) with a MgO Interlayer. Adv. Photonics Res.
**2021**, 2, 2000210. [Google Scholar] [CrossRef] - Ern, V.; Switendick, A.C. Electronic Band Structure of TiC, TiN, and TiO. Phys. Rev.
**1965**, 137, A1927–A1936. [Google Scholar] [CrossRef] - Ahuja, R.; Eriksson, O.; Wills, J.M.; Johansson, B. Structural, Elastic, and High-Pressure Properties of Cubic TiC, TiN, and TiO. Phys. Rev. B
**1996**, 53, 3072–3079. [Google Scholar] [CrossRef] - Delin, A.; Eriksson, O.; Ahuja, R.; Johansson, B.; Brooks, M.S.S.; Gasche, T.; Auluck, S.; Wills, J.M. Optical Properties of the Group-IV B Refractory Metal Compounds. Phys. Rev. B
**1996**, 54, 1673–1681. [Google Scholar] [CrossRef] - Marlo, M.; Milman, V. Density-Functional Study of Bulk and Surface Properties of Titanium Nitride Using Different Exchange-Correlation Functionals. Phys. Rev. B
**2000**, 62, 2899–2907. [Google Scholar] [CrossRef] - Stampfl, C.; Mannstadt, W.; Asahi, R.; Freeman, A.J. Electronic Structure and Physical Properties of Early Transition Metal Mononitrides: Density-Functional Theory LDA, GGA, and Screened-Exchange LDA FLAPW Calculations. Phys. Rev. B
**2001**, 63, 155106. [Google Scholar] [CrossRef] [Green Version] - Catellani, A.; Calzolari, A. Plasmonic Properties of Refractory Titanium Nitride. Phys. Rev. B
**2017**, 95, 115145. [Google Scholar] [CrossRef] [Green Version] - Dal Forno, S.; Lischner, J. Electron-Phonon Coupling and Hot Electron Thermalization in Titanium Nitride. Phys. Rev. Mater.
**2019**, 3, 115203. [Google Scholar] [CrossRef] [Green Version] - Höchst, H.; Bringans, R.D.; Steiner, P.; Wolf, T. Photoemission Study of the Electronic Structure of Stoichiometric and Substoichiometric TiN and ZrN. Phys. Rev. B
**1982**, 25, 7183–7191. [Google Scholar] [CrossRef] - Anderson, C.A.; McKinley, A.; Brown, N.M.D.; Joyce, A.M. A Combined AES, Resonant Photoemission and EELS Study of in-Situ Grown Titanium Nitride. Surf. Sci.
**1997**, 383, 248–260. [Google Scholar] - Harrison, W.A. Parallel-Band Effects in Interband Optical Absorption. Phys. Rev.
**1966**, 147, 467–469. [Google Scholar] [CrossRef] - Ashcroft, N.W.; Sturm, K. Interband Absorption and the Optical Properties of Polyvalent Metals. Phys. Rev. B
**1971**, 3, 1898–1910. [Google Scholar] [CrossRef] - Boyen, H.-G.; Gampp, R.; Oelhafen, P.; Heinz, B.; Ziemann, P.; Lauinger, C.; Herminghaus, S. Intraband Transitions in Simple Metals: Evidence for Non-Drude-like near-IR Optical Properties. Phys. Rev. B
**1997**, 56, 6502–6505. [Google Scholar] [CrossRef] - Ehrenreich, H.; Philipp, H.R.; Segall, B. Optical Properties of Aluminum. Phys. Rev.
**1963**, 132, 1918–1928. [Google Scholar] [CrossRef] - Nguyen, H.V.; An, I.; Collins, R.W. Evolution of the Optical Functions of Thin-Film Aluminum: A Real-Time Spectroscopic Ellipsometry Study. Phys. Rev. B
**1993**, 47, 3947–3965. [Google Scholar] [CrossRef] - Chen, L.-Y.; Lynch, D.W. The Optical Properties of AuAl2 and PtAl2. Phys. Status Solidi
**1988**, 148, 387–394. [Google Scholar] [CrossRef] - Kim, K.J.; Harmon, B.N.; Chen, L.-Y.; Lynch, D.W. Optical Properties and Electronic Structures of the Intermetallic Compounds AuGa2 and PtGa2. Phys. Rev. B
**1990**, 42, 8813–8819. [Google Scholar] [CrossRef] [Green Version] - Spengler, W.; Kaiser, R.; Christensen, A.N.; Müller-Vogt, G. Raman Scattering, Superconductivity, and Phonon Density of States of Stoichiometric and Nonstoichiometric TiN. Phys. Rev. B
**1978**, 17, 1095–1101. [Google Scholar] [CrossRef] - Constable, C.P.; Yarwood, J.; Münz, W.-D. Raman Microscopic Studies of PVD Hard Coatings. Surf. Coat. Technol.
**1999**, 116–119, 155–159. [Google Scholar] [CrossRef] - Stoehr, M.; Shin, C.-S.; Petrov, I.; Greene, J.E. Raman Scattering from TiN
_{x}(0.67 ≤ x ≤ 1.00) Single Crystals Grown on MgO(001). J. Appl. Phys.**2011**, 110, 083503. [Google Scholar] [CrossRef] - Kharitonov, A.V.; Yanilkin, I.V.; Gumarov, A.I.; Vakhitov, I.R.; Yusupov, R.V.; Tagirov, L.R.; Kharintsev, S.S.; Salakhov, M.K. Synthesis and Characterization of Titanium Nitride Thin Films for Enhancement and Localization of Optical Fields. Thin Solid Film.
**2018**, 653, 200–203. [Google Scholar] [CrossRef] - Cheng, P.; Ye, T.; Zeng, H.; Ding, J. Raman Spectra Investigation on the Pressure-Induced Phase Transition in Titanium Nitride (TiN). AIP Adv.
**2020**, 10, 045110. [Google Scholar] [CrossRef] - Kress, W.; Roedhammer, P.; Bilz, H.; Teuchert, W.D.; Christensen, A.N. Phonon Anomalies in Transition-Metal Nitrides: TiN. Phys. Rev. B
**1978**, 17, 111–113. [Google Scholar] [CrossRef] - Isaev, E.I.; Simak, S.I.; Abrikosov, I.A.; Ahuja, R.; Vekilov, Y.K.; Katsnelson, M.I.; Lichtenstein, A.I.; Johansson, B. Phonon Related Properties of Transition Metals, Their Carbides, and Nitrides: A First-Principles Study. J. Appl. Phys.
**2007**, 101, 123519. [Google Scholar] [CrossRef] [Green Version] - Chen, S.; Kühne, P.; Stanishev, V.; Knight, S.; Brooke, R.; Petsagkourakis, I.; Crispin, X.; Schubert, M.; Darakchieva, V.; Jonsson, M.P. On the Anomalous Optical Conductivity Dispersion of Electrically Conducting Polymers: Ultra-Wide Spectral Range Ellipsometry Combined with a Drude–Lorentz Model. J. Mater. Chem. C
**2019**, 7, 4350–4362. [Google Scholar] [CrossRef] [Green Version]

**Figure 1.**(

**a**) Picture of one of the three series of samples; (

**b**) SEM image of a cross-section of the stoichiometric sample; (

**c**) composition of TiN

_{x}samples determined from SIMS experiment as a function of the wavelength, at which the real part of the dielectric function crosses zero; (

**d**) GIXRD patterns proving that the crystal structure $\mathrm{Fm}\overline{3}\mathrm{m}$ is preserved despite changes in composition; (

**e**) EDS spectra proving that there are no other elements than Ti and N; the Si line comes from the substrate.

**Figure 2.**Extracted values of the real (

**a**,

**c**) and imaginary (

**b**,

**d**) part of the dielectric function in the 193 nm to 1.69 μm (

**a**,

**b**) or 1.7 μm to 30 μm (

**c**,

**d**) spectral range. Arrows in Figure (

**b**) point to the optical transitions. Insets in Figures (

**b**,

**d**) show the loss function (minus the imaginary part of the reciprocal dielectric function) as a function of energy.

**Figure 4.**(

**a**) Experimental Raman spectra of all samples and (

**b**) phonon band structure with a corresponding density of states.

# | d (nm) | RMS (nm) | λ@ε_{1} = 0(nm) | x in TiN_{x} − | a_{0}(nm) |
---|---|---|---|---|---|

1 | 151 | 1.02 | 608.0 ± 0.5 | 1.21 ± 0.02 | 0.4260 |

2 | 169 | 0.99 | 572.5 ± 0.5 | 1.16 ± 0.02 | 0.4255 |

3 | 188 | 0.99 | 537.0 ± 0.5 | 1.10 ± 0.01 | 0.4263 |

4 | 230 | 0.96 | 501.0 ± 0.5 | 1.04 ± 0.01 | 0.4280 |

5 | 415 | 2.42 | 479.0 ± 0.5 | 0.99 ± 0.01 | 0.4234 |

6 | 515 | 2.43 | 428.5 ± 0.5 | 0.93 ± 0.02 | 0.4230 |

7 | 542 | 2.46 | 392.5 ± 0.5 | 0.84 ± 0.03 | 0.4220 |

**Table 2.**Values of all parameters that describe the dielectric function $\epsilon $ of all the samples in the range 193 nm to 1.69 μm.

Sample 1 | Sample 2 | Sample 3 | Sample 4 | Sample 5 | Sample 6 | Sample 7 | |
---|---|---|---|---|---|---|---|

${E}_{\mathrm{pu}}$ (eV) | 6.61 | 6.73 | 6.80 | 6.82 | 6.30 | 7.42 | 8.22 |

${\Gamma}_{\mathrm{D}}$ (eV) | 0.66 | 0.63 | 0.61 | 0.57 | 0.71 | 0.91 | 1.30 |

f_{1} | 0.16 | 0.07 | 0.81 | 1.07 | 0.15 | 0.45 | 0.64 |

${E}_{1}$ (eV) | 2.39 | 2.30 | 2.30 | 2.15 | 2.16 | 2.17 | 2.22 |

${\Gamma}_{1}$ (eV) | 0.93 | 0.70 | 1.97 | 1.90 | 0.68 | 1.09 | 1.41 |

f_{2} | 0.63 | 0.26 | 0.54 | 0.56 | 0.56 | 0.28 | - |

${E}_{2}$ (eV) | 3.49 | 3.51 | 3.60 | 3.67 | 3.68 | 3.85 | - |

${\Gamma}_{2}$ (eV) | 1.49 | 1.07 | 1.36 | 1.34 | 1.20 | 1.63 | - |

f_{3} | 5.53 | 6.40 | 2.99 | 2.61 | 2.12 | 2.44 | 1.62 |

${E}_{3}$ (eV) | 5.54 | 5.84 | 5.19 | 5.20 | 5.16 | 5.34 | 5.07 |

${\Gamma}_{3}$ (eV) | 4.73 | 5.44 | 3.27 | 2.86 | 2.41 | 2.85 | 2.62 |

f_{4} | 0.31 | 0.04 | 2.03 | 1.89 | 1.50 | 1.42 | 2.00 |

${E}_{4}$ (eV) | 6.68 | 6.47 | 6.76 | 6.56 | 6.43 | 6.76 | 6.63 |

${\Gamma}_{4}$ (eV) | 1.70 | 0.72 | 3.68 | 3.01 | 2.43 | 2.88 | 3.57 |

**Table 3.**Values of all parameters that describe the dielectric function $\epsilon $ for all the samples in the range of 800 nm–20 μm.

Sample 1 | Sample 2 | Sample 3 | Sample 4 | Sample 5 | Sample 6 | Sample 7 | |
---|---|---|---|---|---|---|---|

${E}_{\mathrm{pu}}$ (eV) | 6.45 | 6.40 | 6.57 | 6.70 | 6.10 | 7.13 | 8.10 |

${\Gamma}_{\mathrm{D}}$ (eV) | 0.71 | 0.57 | 0.58 | 0.47 | 0.35 | 0.68 | 1.19 |

${f}_{0}{E}_{0}^{2}$ (eV) | - | - | 1.32 | 2.41 | 4.97 | 2.07 | 0.93 |

${\Gamma}_{0}$ (eV) | - | - | 0.065 | 0.065 | 0.061 | 0.070 | 0.075 |

Publisher’s Note: MDPI stays neutral with regard to jurisdictional claims in published maps and institutional affiliations. |

© 2021 by the authors. Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (https://creativecommons.org/licenses/by/4.0/).

## Share and Cite

**MDPI and ACS Style**

Judek, J.; Wróbel, P.; Michałowski, P.P.; Ożga, M.; Witkowski, B.; Seweryn, A.; Struzik, M.; Jastrzębski, C.; Zberecki, K.
Titanium Nitride as a Plasmonic Material from Near-Ultraviolet to Very-Long-Wavelength Infrared Range. *Materials* **2021**, *14*, 7095.
https://doi.org/10.3390/ma14227095

**AMA Style**

Judek J, Wróbel P, Michałowski PP, Ożga M, Witkowski B, Seweryn A, Struzik M, Jastrzębski C, Zberecki K.
Titanium Nitride as a Plasmonic Material from Near-Ultraviolet to Very-Long-Wavelength Infrared Range. *Materials*. 2021; 14(22):7095.
https://doi.org/10.3390/ma14227095

**Chicago/Turabian Style**

Judek, Jarosław, Piotr Wróbel, Paweł Piotr Michałowski, Monika Ożga, Bartłomiej Witkowski, Aleksandra Seweryn, Michał Struzik, Cezariusz Jastrzębski, and Krzysztof Zberecki.
2021. "Titanium Nitride as a Plasmonic Material from Near-Ultraviolet to Very-Long-Wavelength Infrared Range" *Materials* 14, no. 22: 7095.
https://doi.org/10.3390/ma14227095