Electron-phonon coupling and hot electron thermalization in titanium nitride

Forno, Stefano Dal; Lischner, Johannes

doi:10.1103/physrevmaterials.3.115203

Cited by 27 publications

(36 citation statements)

References 68 publications

(61 reference statements)

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“…One explanation was that electron–phonon coupling in TiN is exceptionally weak, [ 39 ] and that there is no sub‐picosecond feature because the slow observed dynamics reflect slow cooling of hot carriers. Another hypothesis is that electron–phonon coupling is so fast that the lattice heats up considerably in a sub‐picosecond time scale, [ 42,77 ] similar to that in transition metals like molybdenum, chromium, or ruthenium. [ 78 ] The probe wavelength plays a critical role in the observed dynamics in the first picosecond: TiN and ZrN show sub‐picosecond decay features near the ENZ but not in the metallic region.…”

Section: Overview Of Transient Reflectivitymentioning

confidence: 99%

Broadband Ultrafast Dynamics of Refractory Metals: TiN and ZrN

Diroll

Saha

Shalaev

et al. 2020

Advanced Optical Materials

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Recent work on transition metal nitrides has highlighted their optical properties as alternatives to noble metals employed in plasmonics such as gold (Au). [1-9] Titanium nitride (TiN), zirconium nitride (ZrN), and other plasmonic nitrides such as hafnium nitride (HfN) and tantalum nitride (TaN) are particularly attractive due to their high melting points that bolster stability at higher ambient temperatures [10-12] and/or under higher laser irradiation intensities, [13-16] in addition to their mechanical hardness [17,18] and complementary metal-oxide-semiconductor compatibility. [19-21] Recent work has demonstrated that TiN shows strong local heating compared to Au, [22-24] which may be exploited for photothermal therapy, [25,26] shape-memory effects, [27] thermochromic windows, [28] photoreactions, [29-32] heat transducers or thermophotovoltaic materials, [22,33-37] or photodetection. [38] Implicit in these observations and devices are very different optical responses of metallic nitrides compared to gold-the most similar classical plasmonic material-particularly with regard to the dissipation of heat. Transient reflection spectroscopy offers a window into the dynamics of heating in metal nitrides upon photoexcitation. Previous pump-probe spectroscopy on titanium nitride and other refractory metals has mainly consisted of single pump and probe wavelengths. [39-42] While some broadband transient absorption studies have been performed on these materials, [43] the epsilon-near-zero (ENZ) window where the real part of the dielectric permittivity crosses zero, has thus far remained unexplored. Importantly, based upon earlier spectroscopic investigations of noble metals and heavily doped semiconductors, the largest changes of transient reflectivity are anticipated at ENZ regions. [44-47] Furthermore, earlier works yield contradictory conclusions from ultrafast pump-probe studies. Early data, in which sub-picosecond dynamics were not observed, suggested that electron-phonon coupling in TiN is weak, [39] with electron equilibration with the lattice requiring tens or hundreds of picoseconds in comparison to ≈1 ps in gold. [48-51] Subsequent experiments with high pump fluences were able to observe the fast dynamics, conveying strong electron-phonon coupling resulting in sub-picosecond equilibration of electrons and the lattice. [42] Transition metal nitrides have recently gained attention in the fields of plasmonics, plasmon-enhanced photocatalysis, photothermal applications, and nonlinear optics because of their suitable optical properties, refractory nature, and large laser damage thresholds. This work reports comparative studies of the transient response of films of titanium nitride (TiN), zirconium nitride (ZrN), and gold (Au) under femtosecond excitation. Broadband transient optical characterization helps to adjudicate earlier, somewhat inconsistent reports regarding hot electron lifetimes based upon single wavelength measurements. These pump-probe experiments show sub-picosecond transient dynamics only within the e...

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Section: Overview Of Transient Reflectivitymentioning

confidence: 99%

Broadband Ultrafast Dynamics of Refractory Metals: TiN and ZrN

Diroll

Saha

Shalaev

et al. 2020

Advanced Optical Materials

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“…[53] The absence of a signature of hot carrier decay in the TA data strongly suggests that electron-phonon coupling occurs at the same timescale or faster than our temporal resolution of ≈100 fs. To corroborate this implication, we have calculated the electron-phonon coupling constant (G in W/m 3 K) from litera ture data using Equation ( 2): [36,38,54] …”

Section: Resultsmentioning

confidence: 99%

“…Although G is temperature dependent as well, [60] from theoretical data on TiN and Au we estimate it to be roughly constant in the temperature range in this work. [38] These partial differential equations are solved with a finite element method in COMSOL Multiphysics, from which the spatial T e and T l timeprofiles are extracted (Figure 3ci). The results of the simulations for both HfN and Au nano particles (Figure 3 and Video S1, Supporting Information) show the evolution of the electron and lattice temperatures in time following photoexcitation.…”

Section: T T T T T G T T Q X Y Z T E Ementioning

confidence: 99%

Ultrafast Photoinduced Heat Generation by Plasmonic HfN Nanoparticles

O'Neill

Frehan

Zhu

et al. 2021

Advanced Optical Materials

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carrier generation. [1,2] This has led to sig nificant interest in plasmonic nanostruc tures for photocatalysis, either through local heat generation or as a photo sensitizer. [3,4] Materials in the family of plasmonic transition metal nitrides (e.g., TiN, HfN, NbN, WN) feature high ther momechanical robustness and recently have been proposed for applications requiring extreme operating conditions, such as photothermal catalysis or solar thermophoto voltaics. [5] These materials have high melting points and demonstrate high temperature durability, chemical sta bility, and corrosion resistance, while pre senting an optical response similar to Au or Ag plasmonic nanostructures. [5,6] With a strong response in the visible range, high mechanical hardness, low material cost, [6][7][8][9] and outstanding performance in electro chemical reactions, [10][11][12] the photophysics of these materials requires further research. In the following, we will briefly review the current level of understanding of the photophysics of noble metal plasmonic particles, followed by a discussion on transition metal nitride plasmonic nanoparticles.Light absorption and heat generation by noble metal nano particles can be summarized as follows: first, the local surface plasmon resonance (LSPR) is excited, which lasts several fs and decays by nonradiative dephasing through Landau damp ening (1-100 fs). This process generates hot carriers at regions with high optical absorption (hotspots), the hot carriers subse quently decay by electron-electron scattering (1-100 fs) followed by electron-phonon coupling (0.1-10 ps). Ultimately, phonons dissipate heat to the surroundings (1-10 ns). [4,13,14] There is increasing interest in hot carrier processes, chemical reac tions induced by them, and determining whether the observed changes in chemical reactions are due to lattice heating or hot charge carriers. [15,16] Since elementary chemical transformations typically occur on a 1-100 ps timescale, [17] it is essential to characterize the light induced carrier dynamics and thermal relaxation of plasmonic systems that consist of nonnoble metal materials. Recent studies have shown that in particular hafnium nitride (HfN) performs well at converting light into heat through thermoplas monic relaxation. [18,19] This efficient lightinduced heating likely stems from a less negative real permittivity (ε′) and a higher imaginary permittivity (ε″) of HfN relative to noble metals, leading to a lossy plasmonic response accompanied by lower There is great interest in the development of alternatives to noble metals for plasmonic nanostructures. Transition metal nitrides are promising due to their robust refractory properties. However, the photophysics of these nanostructures, particularly the hot carrier dynamics and photothermal response on ultrafast timescales, are not well understood. This limits their implementation in applications such as photothermal catalysis or solar thermophotovoltaics. In this study, the light-induced relaxation processes in water-dispersed Hf...

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“…The damage in pristine MgO was observed at around 50 TW/cm 2 . Using the two-temperature model approach 14 , 15 for the photo-induced damage in metal and TiN thermodynamic constants reported previously 16 we estimated the heat deposition depth . This corresponds to the thickness of the TiN layer in which the hot electrons rethermalize with the lattice.…”

Section: Resultsmentioning

confidence: 99%

High-harmonic generation in metallic titanium nitride

et al. 2021

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High-harmonic generation is a cornerstone of nonlinear optics. It has been demonstrated in dielectrics, semiconductors, semi-metals, plasmas, and gases, but, until now, not in metals. Here we report high harmonics of 800-nm-wavelength light irradiating metallic titanium nitride film. Titanium nitride is a refractory metal known for its high melting temperature and large laser damage threshold. We show that it can withstand few-cycle light pulses with peak intensities as high as 13 TW/cm2, enabling high-harmonics generation up to photon energies of 11 eV. We measure the emitted vacuum ultraviolet radiation as a function of the crystal orientation with respect to the laser polarization and show that it is consistent with the anisotropic conduction band structure of titanium nitride. The generation of high harmonics from metals opens a link between solid and plasma harmonics. In addition, titanium nitride is a promising material for refractory plasmonic devices and could enable compact vacuum ultraviolet frequency combs.

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Electron-phonon coupling and hot electron thermalization in titanium nitride

Cited by 27 publications

References 68 publications

Broadband Ultrafast Dynamics of Refractory Metals: TiN and ZrN

Broadband Ultrafast Dynamics of Refractory Metals: TiN and ZrN

Ultrafast Photoinduced Heat Generation by Plasmonic HfN Nanoparticles

High-harmonic generation in metallic titanium nitride

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