A Library of Late Transition Metal Alloy Dielectric Functions for Nanophotonic Applications

Abstract

Accurate complex dielectric functions are critical to accelerate the development of rationally designed metal alloy systems for nanophotonic applications, and to thereby unlock the potential of alloying for tailoring nanostructure optical properties. To date, however, accurate alloy dielectric functions are widely lacking. Here, a time‐dependent density‐functional theory computational framework is employed to compute a comprehensive binary alloy dielectric function library for the late transition metals most commonly employed in plasmonics (Ag, Au, Cu, Pd, Pt). Excellent agreement is found between electrodynamic simulations based on these dielectric functions and selected alloy systems experimentally scrutinized in 10 at% composition intervals. Furthermore, it is demonstrated that the dielectric functions can vary in very non‐linear fashion with composition, which paves the way for non‐trivial optical response optimization by tailoring material composition. The presented dielectric function library is thus a key resource for the development of alloy nanomaterials for applications in nanophotonics, optical sensors, and photocatalysis.

Emergent Opportunities with Metallic Alloys: From Material Design to Optical Devices

“…[ 71 ] In fact, a very recent study has adopted this approach to establish a dielectric function library for binary alloys composed of the common coinage and noble metal constituents. [ 72 ] In this section, however, we concentrate on the modeling of ε from the semiclassical perspective, which helps to provide more intuitive and straightforward understanding of the alloy systems.…”

Anisotropic optical response of gold-silver alloys

“…Alloying in photonics is a promising route for obtaining materials properties and functionalities otherwise unachievable with single material-based structures [1][2][3][4] . Combining different chemical elements opens up avenues of possibilities to fine-tune the optical and electronic response of devices for a broad range of applications such as energy harvesting 5 , continuous-wave and pulsed lasing 3,6 , and non-linear optics 7 .…”

“…Combining different chemical elements opens up avenues of possibilities to fine-tune the optical and electronic response of devices for a broad range of applications such as energy harvesting 5 , continuous-wave and pulsed lasing 3,6 , and non-linear optics 7 . In the last decade, the rapid progress of the plasmonic field occurred due to the advance of new techniques of fabrication and characterization of pure metallic structures 4,8 . More recently, a change of paradigm driven by the maturing of nanofabrication methods and the systematic analysis of alloyed nanostructured systems [9][10][11] resulted in the rise of applications of this novel system as plasmonic tweezers 12 , hydrogen sensors 13 , photocatalystis 14 , and bio-sensors 15 .…”

“…For pure metals, the permittivity is well described in the literature. However, for alloys, there is a lack of fundamental knowledge and agreement about the physical processes underlying their optical response 4 .…”

“…Here, there was no consensus among fitted parameters, leading to differences in the description of the visible and near ultra-violet optical responses 9 . Finally, in a parameter-less fashion, ab-initio methods such as the density functional theory (DFT) were used to elucidate several aspects of the optical properties of alloys 4,21,22 . The advantage of using computational approaches lies in the fact that it is a much faster route to predict materials properties than the traditional fabrication and measurement methods.…”