Surface Plasmon Polaritons and Screened Plasma Absorption in Indium Tin Oxide Compared to Silver and Gold

Abstract

This study addresses the ability of a conducting metal oxide to act as a material capable of supporting surface plasmon polaritons (SPPs). By use of a two-phase Fresnel model that provides insight into the difference between polariton-induced and absorptive decreases in reflectivity, indium tin oxide (ITO) is compared to the noble metals gold and silver, which are widely used as materials for surface plasmon resonance (SPR) detection of analytes. The study builds on application of the Drude free electron model that provides an explanation for the observed optical extinctions as a function of ITO film thickness, including the dependence of wavenumber on angle, by use of only two adjustable parameters, the plasma frequency ωp and the damping Γ. Herein, models of the dispersion and absorption include both the real and imaginary parts of the dielectric function to obtain the plasma absorption spectra and dispersion curves for ITO, Ag, and Au. ITO is found to have surface plasmon dispersion curves and plasma absorption free from interband transitions as observed in Ag but not Au. Au has significant contribution from bound electrons that damps the plasma absorption and broadens the dispersion curve of the SPP. Ag is more like a free-electron conductor than Au but still has some absorption in the frequency range above the observed surface plasmon. ITO is a nearly ideal free-electron conductor.

Application of well-defined indium tin oxide nanorods as Raman active platforms

“…18,19 Therefore, it is highly likely that surface plasmons play a significant role in the enhanced Raman signal observed on ITO NRs, similar to what has been extensively reported in metallic nanoparticles. 28 Unlike the 2D ITO systems reported in the literature, our 1D ITO NRs present an extremely high aspect ratio, and this shape factor can be particularly useful for SERS.…”

“…3,[10][11][12][13] And more recently, other systems involving either a metal oxide thin film or a hybrid system of a metal nanoparticle/metal oxide thin film have been demonstrated as SERS-active materials. 7,[14][15][16][17][18][19] Plasmonic characteristics similar to those observed from noble metals are found in some transparent conducting metal oxides such as indium tin oxide, fluorine-doped tin oxide, and aluminum-doped zinc oxide. 18,20 Despite many leading efforts on this aspect, only a small subset of research discusses Raman enhancement effects observed from nanomaterials that are precisely controlled for their physical, chemical, optical, or electrical properties during synthesis.…”

“…7,14-19 Plasmonic characteristics similar to those observed from noble metals are found in some transparent conducting metal oxides such as indium tin oxide, fluorine-doped tin oxide, and aluminum-doped zinc oxide. 18,20 Despite many leading efforts on this aspect, only a small subset of research discusses Raman enhancement effects observed from nanomaterials that are precisely controlled for their physical, chemical, optical, or electrical properties during synthesis. Controlling the exact size and structure of the nanomaterials has not been the primary focus of many previous SERS studies, and many of the studies involve random surface roughening of Raman substrates for desired surface enhancement effect.…”

Optical absorption of hyperbolic metamaterial with stochastic surfaces

“…TiN also shows similar behavior, except that the transition happens at 545 nm wavelength. In addition, ITO particles are metallic-like in the wavelengths longer than 1.4 µm [26,27]. So a valley appears in the reflectance for the sample coated with the six fold increase of ITO particles which are equivalent to a rough ITO film.…”

Energy harvesting in semiconductor-insulator-semiconductor junctions through excitation of surface plasmon polaritons

“…8,11,12 Because semiconductors do not have bound-state absorption transitions in their band-gaps, their SPP losses can be even smaller in the near infrared (NIR) region than those in conventional plasmonic materials at corresponding visible wavelengths. 13 On the other hand, the carrier density and the refractive index in these materials can also be tuned in a broad range by an applied electric field. 14 In this paper, robust semiconductor-insulator-semiconductor (SIS) junctions have been used to fabricate plasmonic-based solar cell, in which the top TCO layer is a degenerate semiconductor, such as AZO.…”