Tunable optical and plasmonic response of Au nanoparticles embedded in Ta-doped TiO2 transparent conducting films

Abstract

Localised Surface Plasmon Resonances (LSPR) are fascinating optical phenomena occurring in metal nanostructures, like gold nanoparticles (Au NPs). Plasmonic excitation can be tailored efficiently in the visible range by acting on size, shape and NP surrounding, whereas carrier density is fixed, thus restricting the LSPR modulation. Transparent Conductive Oxides (TCOs), on the other hand, are gaining increasing interest for their transparency, charge carrier tunability and plasmonic features in the infrared. The combination of these two materials into a metal-TCO nanocomposite can give access to unique electrical and optical characteristics, to be tailored in view of the desired optoelectronic application. In this study Au NPs and Ta-doped TiO2 TCO films have been merged with the aim to master the Au plasmon resonance by acting on the dielectric properties of the surrounding TCO. Morphology, structure and electrical properties have been investigated as well, in order to understand the optical response of the nano-systems. The role of the embedding geometry has been explored, revealing that the largest LSPR shift (550-760 nm) occurs when the nanoparticles are sandwiched in the middle of the film, and not at the "bottom" of the film (substrate/film interface). Ta doping in the TCO has been varied (5-10% at. and bare TiO2) to induce a permittivity change of the matrix. As a result, Au LSPR is clearly blue-shifted when decreasing the dielectric permittivity at higher Ta content in the sandwich configuration. Despite the non-optimal electrical performance caused by defectivity of the films, Au-Ta:TiO2 multifunctional nanocomposites are promising candidates for their optical behavior as highly tunable plasmonic conductive metamaterials for advanced light management.

Synthesis of Copper Nanosheets Coatings onto Glass and Glass/CrSe2 Substrates Using Ion Coating Technique for Terahertz Technology

“…The transmittance values observed here are close to those reported for the highly conductive TiO 2 films employed in plasmonic devices. [ 2 ] Measurements of transmittance near 500 nm for Cu/Ag/Au, Au/Ag/Au and Au/Pt/Au transparent films used in optoelectronic technology reported T values of 40%, 62% and 55%, respectively. [ 4 ] Cu nanosheets studied here exhibited transmittance values of 75%, 65%, and 51% for nanosheets of thicknesses of 60, 125, and 250 nm, respectively.…”

“…The dielectric constant is determined from the refractive index (n) using Fresnel's equations for light entering normal to the plane. The following relations lead to the identification of the real (𝜀 r ) and imaginary (𝜀 im ) parts of dielectric constant and terahertz cutoff frequency (f T ) [21,22] R = (n − 1) 2 + (𝛼𝜆∕ (4𝜋)) 2 (n + 1) 2 + (𝛼𝜆∕ (4𝜋)) 2 (2)…”

“…Examples of these materials include indium tin oxide (ITO), NO 2 , AuCl 3 , and Ta-doped TiO 2 . [1,2] Each of DOI: 10.1002/crat.202300231 these materials has specific features and suits particular application. However, the limited chemical and thermodynamic stability, poor flexibility, and high refractive index are series problems of these transparent conductors.…”

Plasmonic Photoresistor Based on Interconnected Metal‐Semiconductor Grating

“…[ 59 ] Our method of combining amorphous titania films alongside the plasmonics of the metallic bars opens up new perspectives on the optoelectronic properties of such conjugate systems. [ 60 ] Because of the long‐range atomic disorder; such amorphous titania can play an essential role in photocatalytic performances, such as water splitting or photodegradation of organic materials, as reported by Liang's group. [ 52 ] By linking theoretical modeling, angle‐resolved spectroscopy, and angle‐resolved photocurrent measurement, we have successfully identified the hybrid plasmonic modes and determined their current modulation efficiency (CME).…”