Near-zero negative real permittivity in far ultraviolet: extending plasmonics and photonics with B1-MoNx

CMOS-compatible, refractory conductors are emerging as the materials that will advance novel concepts into real, practical plasmonic technologies. From the available pallet of materials, those with negative real permittivity at very short wavelengths are extremely rare; importantly, they are vulnerable to oxidation—upon exposure to far-UV radiation—and nonrefractory. Epitaxial, substoichiometric, cubic MoN (B1-MoNx) films exhibit resistivity as low as 250 μΩ cm and negative real permittivity for experimental wavelengths as short as 155 nm, accompanied with unparalleled chemical and thermal stabilities, which are reported herein. Finite-difference time domain calculations suggest that B1-MoNx operates as an active plasmonic element deeper in the UV (100–200 nm) than any other known material, apart from Al, while being by far more stable and abundant than any other UV plasmonic conductor. Unexpectedly, the unique optical performance of B1-MoNx is promoted by nitrogen vacancies, thus changing the common perception on the role of defects in plasmonic materials

Highly oriented δ-Bi2O3 thin films stable at room temperature synthesized by reactive magnetron sputtering

We report the synthesis by reactive magnetron sputtering and structural characterization of highly (111)-oriented thin films of δ–Bi2O3. This phase is obtained at a substrate temperature of 150–200 °C in a narrow window of O2/Ar ratio in the sputtering gas (18%–20%). Transmission electron microscopy and x-ray diffraction reveal a polycrystalline columnar structure with (111) texture. The films are stable from room temperature up to 250 °C in vacuum and 350 °C in ambient air

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We report the synthesis by reactive magnetron sputtering and structural characterization of highly (111)-oriented thin films of δ–Bi2O3. This phase is obtained at a substrate temperature of 150–200 °C in a narrow window of O2/Ar ratio in the sputtering gas (18%–20%). Transmission electron microscopy and x-ray diffraction reveal a polycrystalline columnar structure with (111) texture. The films are stable from room temperature up to 250 °C in vacuum and 350 °C in ambient air

Experimental and theoretical investigation of Cr_1-xSc_xN solid solutions for thermoelectrics

The ScN- and CrN-based transition-metal nitrides have recently emerged as a novel and unexpected class of materials for thermoelectrics. These materials constitute well-defined model systems for investigating mixing thermodynamics, phase stability, and band structure aiming for property tailoring. Here, we demonstrate an approach to tailor their thermoelectric properties by solid solutions. The trends in mixing thermodynamics and densities-of-states (DOS) of rocksalt-Cr1-xScxN solid solutions (0 ≤ x ≤ 1) are investigated by first-principles calculations, and Cr1-xScxN thin films are synthesized by magnetron sputtering. Pure CrN exhibits a high power factor, 1.7 × 10-3 W m-1 K-2 at 720 K, enabled by a high electron concentration thermally activated from N vacancies. Disordered rocksalt-Cr1-xScxN solid solutions are thermodynamically stable, and calculated DOS suggest the possibility for power-factor improvement by Sc3d orbital delocalization on Cr3d electrons giving decreasing electrical resistivity, while localized Cr3d orbitals with a large DOS slope may yield an improved Seebeck coefficient. Sc-rich solid solutions show a large improvement in power factor compared to pure ScN, and all films have power factors above that expected from the rule-of-mixture. These results corroborate the theoretical predictions and enable tailoring and understanding of structure-transport-property correlations of Cr1-xScxN. © 2016 Author(s)