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Proceedings Paper

Thick epsilon-near-zero metamaterial film (Conference Presentation)
Author(s): Jimmy Ni; Wendy Sarney; Asher Leff; James Cahill; Weimin Zhou

Paper Abstract

Indium Tin Oxide (ITO) has shown significant potential in becoming a candidate for ε-near-zero (ENZ) metamaterial which can be a host material for EMNZ devices. However, the ENZ ITO material itself has not been thoroughly studied at a device level for several reasons. So far, only relatively thin (hundred nm scale) annealed ITO film has been studied for ENZ purposes. We put an initial effort in characterizing the 2 µm-thick ITO film in respect to its permittivity (ε). The melting point for indium is between 350 C and 400 C, so the annealing temperature falls into this window. A series of 2 µm-thick ITO films were deposited on a 3 µm-thick SiO2 on Si wafer that were annealed at different temperatures and times. These sample were further investigated by a cutting-edge ellipsometry technology. The optical constant depth profile at 1550 nm is measured for various annealing temperature and periods. The results show that both real and imaginary part of permittivity are non-uniform along the growth direction. Under a specific processing window, we are able to achieve a micron-scale of epsilon near-zero ITO film. We also conducted a TEM study to investigate the physical structure of the material. We find the evidence of different partial crystallization across the entire ITO film. The cross-section TEM with low magnification to show entire depth profile of the ITO from the SiO2 interface to the top surface. TEM images show evidence for the different crystal morphology across the ITO film, as the crystal grains varies for different regions of ITO.

Paper Details

Date Published: 9 September 2019
Proc. SPIE 11080, Metamaterials, Metadevices, and Metasystems 2019, 110801Z (9 September 2019); doi: 10.1117/12.2529520
Show Author Affiliations
Jimmy Ni, U.S. Army Research Lab. (United States)
Wendy Sarney, U.S. Army Research Lab. (United States)
Asher Leff, U.S. Army Research Lab. (United States)
James Cahill, U.S. Army Research Lab. (United States)
Weimin Zhou, U.S. Army Research Lab. (United States)

Published in SPIE Proceedings Vol. 11080:
Metamaterials, Metadevices, and Metasystems 2019
Nader Engheta; Mikhail A. Noginov; Nikolay I. Zheludev, Editor(s)

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