Surface roughness and substrate induced symmetry-breaking: influence on the plasmonic properties of aluminum nanostructure arrays (original) (raw)
Related papers
Plasmonic Breathing and Edge Modes in Aluminum Nanotriangles
ACS Photonics, 2017
We use electron energy loss spectroscopy (EELS) to perform a comprehensive spectroscopy and mapping of the plasmonic modes sustained by aluminum nanotriangles. Behind the apparent simplicity of such structures, a rich variety of plasmonic modes is observed. Edge modes and pseudoradial breathing modes (pseudo-RBMs) are unveiled as they couple efficiently with the electron source. We propose analytical models confirmed by rigorous simulations to index both families of modes and describe their spatial symmetry. Edge modes could be indexed as nanoantenna modes, while pseudo-RBMs match triangular cavities ones. The dispersion relation of both modes is measured highlighting their different nature. Plasmonic resonances ranging from near-infrared (IR) to ultraviolet (UV) are obtained by varying the triangle sizes, and especially, we found pseudo-RBMs resonances in the UV region, making them interesting for UV applications.
Localization, Hybridization, and Coupling of Plasmon Resonances in an Aluminum Nanomatryushka
In this study, we investigate the plasmon response of two concentric aluminum (Al) nanoshells as a nanomatryushka unit to introduce a novel compositional structure that has a strong potential to employ in designing practical nanoscale plasmonic devices. Herein, we employed Al nanoshells with a coverage of oxide (Al 2 O 3) layer with certain and homogenous size of thickness in inner and outer sides. Using plasmon hybridization theory and finite-difference time-domain (FDTD) method as numerical model, we calculated and sketched the optical response and energy level diagram for the studied structure. Strong plasmon resonances are reported in the UV and visible wavelengths that can be supported efficiently by using the proposed nanomatryushka unit composed of Al/Al 2 O 3 on a SiO 2 surface. Utilizing presented nanomatryushka in designing an artificial dimer configuration, the possibility of appearing of dark modes and formation of Fano resonances in such a symmetric structure in the UV and visible spectra are verified numerically. Immersing the presented dimer in various liquids with different refractive indices, the behavior of Fano dip is investigated and corresponding figure of merit (FoM) is quantified based on the plasmon resonance energy shifts over the refractive index variations. This understating opens novel avenues to obtain sharp and deep Fano resonances in simple and low-cost structures that have strong potentials in fabrication of biochemical sensors, superlensing, and biological agents.
ACS Nano, 2014
Unlike silver and gold, aluminum has material properties that enable strong plasmon resonances spanning much of the visible region of the spectrum and into the ultraviolet. This extended response, combined with its natural abundance, low cost, and amenability to manufacturing processes, makes aluminum a highly promising material for commercial applications. Fabricating Al-based nanostructures whose optical properties correspond with theoretical predictions, however, can be a challenge. In this work, the Al plasmon resonance is observed to be remarkably sensitive to the presence of oxide within the metal. For Al nanodisks, we observe that the energy of the plasmon resonance is determined by, and serves as an optical reporter of, the percentage of oxide present within the Al. This understanding paves the way toward the use of aluminum as a low-cost plasmonic material with properties and potential applications similar to those of the coinage metals.
Mode coupling in arrays of Al nanoparticles
Journal of Quantitative Spectroscopy and Radiative Transfer, 2020
The mechanisms of coupling between the lattice modes of a two-dimensional (2D) array consisting of Al nanoparticles and the localized modes of individual Al nanoparticles have been studied in detail. The results have been obtained employing the finite-difference time-domain method (FDTD) and the generalized Mie theory. It was shown that interactions of single particles with 2D lattice modes significantly change the extinction spectra depending on the particle radius and the lattice period. The Rayleigh anomalies of higher orders contribute to formation of hybrid modes resulting in increase of the extinction efficiency in short wavelength range of the spectrum. It is shown that high intensity magnetic modes are excited in aluminum nanoparticles arrays. The patterns of spatial electromagnetic field distribution at the frequencies of hybrid modes have been studied. We note that comprehensive understanding the mode coupling mechanisms in arrays paves the way for engineering different types of modern photonic devices with controllable optical properties.
Hybrid modes in Al nanoparticles arrays
2020
The mechanisms of coupling between the lattice modes of a two-dimensional (2D) array consisting of Al nanoparticles and the localized modes of individual Al nanoparticles have been studied in detail. The results have been obtained employing the finite-difference time-domain method (FDTD) and the generalized Mie theory. It was shown that interactions of single particles with 2D lattice modes significantly change the extinction spectra depending on the particle radius and the lattice period. The Rayleigh anomalies of higher orders contribute to formation of hybrid modes resulting in increase of the extinction efficiency in short wavelength range of the spectrum. It is shown that high intensity magnetic modes are excited in aluminum nanoparticles arrays. The patterns of spatial electromagnetic field distribution at the frequencies of hybrid modes have been studied. We note that comprehensive understanding the mode coupling mechanisms in arrays paves the way for engineering different ty...
In this study, a quadrumer cluster composed of Al nanodisks in both symmetric and antisymmetric orientations has been utilized to generate magnetic hot-spots by using coil-type Fano resonances. Determining the accurate geometrical sizes for the examined cluster, we calculated the spectral response of the structure numerically. Utilizing strong plasmon resonance hybridization between Al/Al 2 O 3 nanodisks that are suited in a close proximity to each other, such a finite and simple nanocluster yields intensified hidden magnetic fields |H| as a dark mode and electric |E| as a bright modes. Using and placement of silicon nanospheres in the unoccupied gap distance between proximal Al nanodisks give rise to significant enhancement in the energy and quality of the induced multiple Fano dips. Appearing of multiple Fano resonant modes in a coil-type regime in the UV and visible spectrum helps us to optimize the energy of generated magnetic hot-spots, significantly. Ultimately, we examined the sensitivity of the proposed final quadrumer by considering the behavior of Fano minima. We plotted the linear figure of merit (FoM) based on the Fano resonance energy differences in various conditions over the refractive index. Quantifying the FoM for the studied nanostructure, then we compared the quality of structure with the analogous nanoclusters. This work paves novel methods toward the utilization of Al/Al 2 O 3 nanoparticles as a potential substance to employ in designing nanoclusters that are able to support strong dark resonances as well as bright modes. Wide-range working region, optimized electric and magnetic fields, multiple and high quality Fano dips, high FoM and low-costs are the superior features of the proposed artificial structure in comparison to analogous configurations.
Surface roughness effects on aluminium-based ultraviolet plasmonic nanolasers
Scientific Reports, 2017
We systematically investigate the effects of surface roughness on the characteristics of ultraviolet zinc oxide plasmonic nanolasers fabricated on aluminium films with two different degrees of surface roughness. We demonstrate that the effective dielectric functions of aluminium interfaces with distinct roughness can be analysed from reflectivity measurements. By considering the scattering losses, including Rayleigh scattering, electron scattering, and grain boundary scattering, we adopt the modified Drude-Lorentz model to describe the scattering effect caused by surface roughness and obtain the effective dielectric functions of different Al samples. The sample with higher surface roughness induces more electron scattering and light scattering for SPP modes, leading to a higher threshold gain for the plasmonic nanolaser. By considering the pumping efficiency, our theoretical analysis shows that diminishing the detrimental optical losses caused by the roughness of the metallic interface could effectively lower (~33.1%) the pumping threshold of the plasmonic nanolasers, which is consistent with the experimental results.
Al clusters have drawn tremendous attention of scientific community for their characteristic deep ultraviolet plasmonic emission. In this study, we have explored the plasmonic characteristics of a series of linear (Aln; n = 2 to 9) and cyclic aluminum clusters (n = 3,4) along with our recently reported three Al13+ isomer system [Guin et. al. Journal of Molecular Graphics and Modeling, 2020, 97, 107544] and corresponding alkali doped clusters [Guin et. al. Journal of Molecular Modeling, 2021, 27, 235]. Among the three Al13+ isomers one is perfectly planar (CI) and two others are quasi-planar clusters (CT and CII). It is a well-known fact that properties of nano-clusters strongly depend on the size and shape of the clusters. The current study reveals that for the linear chains the plamonic character systematically increases with the nuclearity of the clusters. For the cyclic clusters (Al3 and Al4) the plamonicity is lower compared to corresponding linear clusters. In case of Al13+ iso...
ACS Nano, 2011
Localized surface plasmon resonances (LSPR) are collective electronic excitations in metallic nanoparticles. The LSPR spectral peak position, as a function of nanoparticle size and material, is known to depend primarily on dynamic depolarization and electron structure related effects. The former gives rise to the well-known spectral red shift with increasing nanoparticle size. A corresponding understanding of the LSPR spectral line width for a wide range of nanoparticle sizes and different metals does, however, not exist. In this work, the radiative and nonradiative damping contributions to the LSPR line width over a broad nanoparticle size range (40À500 nm) for a selection of three metals with fundamentally different bulk dielectric properties (Au, Pt, and Al) are explored experimentally and theoretically. Excellent agreement was obtained between the observed experimental trends and the predictions based on electrostatic spheroid theory (MLWA), and the obtained results were successfully related to the specific band structure of the respective metal. Moreover, for the first time, a clear transition from a radiation damping dominated to a quenched radiation damping regime (subradiance) in large nanoparticles was observed and probed by varying the electron density through appropriate material choice. To minimize inhomogeneous broadening (commonly present in ensemble-based spectroscopic measurements), a novel, electron-beam lithography (EBL)-based nanofabrication method was developed. The method generates large-area 2D patterns of randomly distributed nanodisks with well-defined size and shape, narrow size distribution, and tunable (minimum) interparticle distance. In order to minimize particleÀparticle coupling effects, sparse patterns with a large interparticle distance (center-to-center g6 particle diameters) were considered.