Effective negative capacitance has been postulated in ferroelectrics because there is a hysteresis in plots of polarization-electric field. Compelling experimental evidence of effective negative capacitance is presented here at room temperature in engineered devices, where it is stabilized by the presence of a paraelectric material. In future integrated circuits, the incorporation of such negative capacitance into MOSFET gate stacks would reduce the subthreshold slope, enabling low power operation and reduced self-heating.
Using
localized surface plasmon resonances (LSPR) to focus electromagnetic
radiation to the nanoscale shows the promise of unprecedented capabilities
in optoelectronic devices, medical treatments and nanoscale chemistry,
due to a strong enhancement of light-matter interactions. As we continue
to explore novel applications, we require a systematic quantitative
method to compare suitability across different geometries and a growing
library of materials. In this work, we propose application-specific
figures of merit constructed from fundamental electronic and optical
properties of each material. We compare 17 materials from four material
classes (noble metals, refractory metals, transition metal nitrides,
and conductive oxides) considering eight topical LSPR applications.
Our figures of merit go beyond purely electromagnetic effects and
account for the materials’ thermal properties, interactions
with adjacent materials, and realistic illumination conditions. For
each application we compare, for simplicity, an optimized spherical
antenna geometry and benchmark our proposed choice against the state-of-the-art
from the literature. Our propositions suggest the most suitable plasmonic
materials for key technology applications and can act as a starting
point for those working directly on the design, fabrication, and testing
of such devices.
Titanium oxynitride (TiON) thin films are fabricated using reactive magnetron sputtering. The mechanism of their growth formation is explained, and their optical properties are presented. The films grown when the level of residual oxygen in the background vacuum was between 5 nTorr to 20 nTorr exhibit double epsilon-near-Zero (2-ENZ) behavior with ENZ1 and ENZ2 wavelengths tunable in the 700-850 and 1100-1350 nm spectral ranges, respectively. Samples fabricated when the level of residual oxygen in the background vacuum was above 2 × 10 Torr exhibit nonmetallic behavior, while the layers deposited when the level of residual oxygen in the background vacuum was below 5 × 10 Torr show metallic behavior with a single ENZ value. The double ENZ phenomenon is related to the level of residual oxygen in the background vacuum and is attributed to the mixture of TiN and TiON and TiO phases in the films. Varying the partial pressure of nitrogen during the deposition can further control the amount of TiN, TiO, and TiON compounds in the films and, therefore, tune the screened plasma wavelengths. A good approximation of the ellipsometric behavior is achieved with Maxwell-Garnett theory for a composite film formed by a mixture of TiO and TiN phases suggesting that double ENZ TiON films are formed by inclusions of TiN within a TiO matrix. These oxynitride compounds could be considered as new materials exhibiting double ENZ in the visible and near-IR spectral ranges. Materials with ENZ properties are advantageous for designing the enhanced nonlinear optical response, metasurfaces, and nonreciprocal behavior.
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