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Due to their chemical stability, the large tunability and the mechanical resistance, metal-oxides and metal-nitrides are quickly gaining a privileged role in the realm of plasmonics and photonics, as alternative to standard noble metals in the IR-visible range.
Here, by using first principles approaches, we study the optoelectronic and plasmonic properties of representative samples belonging to these two classes of materials. We first investigate the origin of near-infrared plasmonic activity of several metal-oxides: transparent conducting oxides (TCO), such as Al-ZnO and Ta-TiO2, and phases change materials (PCM), namely VO2. In the former case, we investigate the microscopic effects of metal doping (e.g. Al, Ta) [1] and defects (e.g. vacancies) [2] on the optical and electronic properties of TCOs and how this reflects on the plasmonic response of surface-plasmon polaritons or layered hyperbolic metamaterials, in connection with other dielectric media. In the latter case, we focus on stacked heterostructures resulting from the coexistence of metallic and semiconducting phases of VO2. This joint-phase combination, which has been experimentally realized, gives rise to a natural hyperbolic metamaterial, which supports the propagation of volume-plasmon-polariton TM waves (Figure 1) [3]. In the second part of the presentation, we will discuss the plasmonic properties of refractory metal nitrides (e.g. TiN). We first investigate the plasmon dispersion relations of TiN bulk [4] and we predict the stability of surface-plasmon polaritons at different TiN/dielectric interfaces proposed by recent experiments. Finally, by combining first-principles theoretical calculations and experimental optical and structural characterization techniques, we study the plasmonic properties of ultrathin TiN films (2-10 nm) at an atomistic level for the realization of ultrathin metasurfaces with plasmonic nonlinear properties [5-6].
References:
[1] A. Calzolari, et al., ACS Photonics 1, 703 (2014).
[2] S. Benedetti, et al., Phys. Chem. Chem. Phys. 19, 29364 (2017).
[3] M. Eaton, et al., Opt. Express 26, 5342 (2018).
[4] A. Catellani and A. Calzolari, Phys. Rev. B 95, 115145 (2017).
[5] D. Shah, et al., ACS Photonics 5, 2816 (2018).
[6] A. Catellani and A. Calzolari, Opt. Mater. Exp. (2019), in press.
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