cm9b02917_si_001.pdf (2.33 MB)
Dopant Selection Strategy for High-Quality Factor Localized Surface Plasmon Resonance from Doped Metal Oxide Nanocrystals
journal contribution
posted on 2019-09-09, 19:14 authored by Bharat Tandon, Sandeep Ghosh, Delia J. MillironThin
films of degenerately doped metal oxides such as those of
Sn-doped In2O3 (Sn:In2O3) are commercially significant for their broad utilization as transparent
conducting electrodes in optoelectronic devices. Over the past decade,
nanocrystals (NCs) of Sn:In2O3 and other doped
metal oxides have also attracted interest for localized surface plasmon
resonance (LSPR) that occurs in the near- to mid-infrared region.
The suitability of this LSPR for some applications depends on its
capacity to concentrate light in small regions of space, known as
near-field hot spots. This efficiency to create near-field hot spots
can be judged through an LSPR figure-of-merit such as Quality factor
(Q-factor), defined as the ratio of LSPR peak energy to its line width.
The free electron density determines the LSPR peak energy, while the
extent of electron scattering controls the LSPR line width; hence,
these factors together essentially dictate the value of the Q-factor.
An unfortunate trade-off arises when dopants are introduced since
the aliovalent dopants generating the free electrons (increasing LSPR
energy) also act as centers of scattering of electrons (increasing
LSPR line width), thereby decreasing the LSPR Q-factor. Dopant selection
is hence of paramount importance to achieve a high value of LSPR Q-factor.
Here, we describe the properties of aliovalent cationic dopants that
allow both high LSPR energy and low LSPR line width and, subsequently,
high LSPR Q-factor. In this context, we identify Zr4+ as
a model aliovalent dopant for high LSPR Q-factor in the In2O3 lattice. The resulting Zr-doped In2O3 NCs exhibit one of the highest LSPR Q-factors reported in
the mid-infrared region while also performing equivalently to the
recognized materials for either high dopant activation (Sn:In2O3 NCs) or low LSPR line width (Ce-doped In2O3 NCs) simultaneously. The Zr donor level is positioned
well inside the conduction band of In2O3, and
Zr doping is surface segregated, both minimizing electron scattering.
The combination of this low electron scattering and high dopant activation
of Zr4+ ions is responsible for the high LSPR Q-factors.
These strategies can be used to design a variety of doped metal oxide
NC systems exhibiting high LSPR Q-factors.
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High-Quality Factor Localized Surface Plasmon Resonancedopant activation2 O 3 latticeLSPR line widthmetal oxide NC systems2 O 3 NCs exhibitZr donor levelDoped Metal Oxide NanocrystalsDopant Selection Strategymid-infrared regionLSPR Q-factorsmetal oxidesmodel aliovalent dopantLSPR Q-factorsurface plasmon resonance2 O 3LSPR peak energyLSPR energyaliovalent cationic dopants2 O 3 NCs
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