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11 results on '"Engheta, Nader"'

5. Quadrupole-Enhanced Raman Scattering

Author

Hastings, Simon P., primary, Swanglap, Pattanawit, additional, Qian, Zhaoxia, additional, Fang, Ying, additional, Park, So-Jung, additional, Link, Stephan, additional, Engheta, Nader, additional, and Fakhraai, Zahra, additional

Published
2014
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11. Solution-Processed Phase-Change VO2Metamaterials from Colloidal Vanadium Oxide (VOx) Nanocrystals

Author

Paik, Taejong, Hong, Sung-Hoon, Gaulding, E. Ashley, Caglayan, Humeyra, Gordon, Thomas R., Engheta, Nader, Kagan, Cherie R., and Murray, Christopher B.

Abstract

We demonstrate thermally switchable VO2metamaterials fabricated using solution-processable colloidal nanocrystals (NCs). Vanadium oxide (VOx) NCs are synthesized through a nonhydrolytic reaction and deposited from stable colloidal dispersions to form NC thin films. Rapid thermal annealing transforms the VOxNC thin films into monoclinic, nanocrystalline VO2thin films that show a sharp, reversible metal–insulator phase transition. Introduction of precise concentrations of tungsten dopings into the colloidal VOxNCs enables the still sharp phase transition of the VO2thin films to be tuned to lower temperatures as the doping level increases. We fabricate “smart”, differentially doped, multilayered VO2films to program the phase and therefore the metal–insulator behavior of constituent vertically structured layers with temperature. With increasing temperature, we tailored the optical response of multilayered films in the near-IR and IR regions from that of a strong light absorber, in a metal–insulator structure, to that of a Drude-like reflector, characteristic of a pure metallic structure. We demonstrate that nanocrystal-based nanoimprinting can be employed to pattern multilayered subwavelength nanostructures, such as three-dimensional VO2nanopillar arrays, that exhibit plasmonic dipolar responses tunable with a temperature change.

Published
2014
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