Abstract
We report fabrication and characterization of large-area ultrathin near-infrared light absorbers and scatterers based on a mono-layer of gold nanoparticles laying on top of a dielectric spacer and an aluminum reflector. The nanoparticles are formed through thermal annealing of an evaporated continuous gold film. Through optimization of initial gold-film thickness, spacer thickness, as well as annealing temperature we obtained samples that exhibit very low (~2%) broadband specular reflectance at near-infrared (NIR) wavelength range. By considering also diffuse reflection, we identify that the low specular reflectance can be due to either relatively high light absorption (~70%) or high light scattering (over 60%), with the latter achieved for samples having relatively sparse gold nanoparticles. Both strong absorption and scattering of NIR light are not inherent properties of the bulk materials used for fabricating the samples. Such composite optical surfaces can potentially be integrated to solar-energy harvesting and LED devices.
Highlights
Optical properties of metals can be strongly altered through structuring at nanoscale
It is known that plasmonic nanostructures can serve as efficient antennas at optical frequencies, as evidenced by recent studies on optical Yagi-Uda antenna [14], superscatterers [15] and phasediscontinuous metamaterial surfaces [16]
By closely examining the particle-size distribution, we identify that strong diffuse light reflection is achieved when gold nanoparticles have a relatively sparse distribution
Summary
Optical properties of metals can be strongly altered through structuring at nanoscale. We start with a similar initial geometry including a bottom metal reflector, a dielectric spacer, and a top gold-nanoparticle layer, with the latter two layers’ thicknesses increased compared to those in [19]; thermal annealing at various temperatures is carried out to study NIR responses of the obtained samples. We observed that such a sample can possess a strong extinction (1−R, where R is specular reflectance) band centered just over 1 μm wavelength with a full-width at half-maximum of approximately 1 μm. Such large-area and cost-effective metamaterial surfaces can be potentially used in optoelectronic applications: strong light absorption (or minimum total reflection) can be used for e.g. solar thermal collectors; strong diffuse light reflection (with minimum loss) can be used for reflection-plane design of photovoltaic cells and LED devices
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callMore From: Journal of the European Optical Society-Rapid Publications
Disclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
