Diameters Of Nanodisks Research Articles

Flexible tuning of the peak wavelength and intensity of localized surface plasmon resonance by heat treatment of nanodisk structures fabricated by electron beam lithography

We demonstrate that the plasmonic properties of Au nanodisk structures fabricated by an electron beam lithography can be improved by very simple heat treatments, and that the resonance wavelength can be tuned by temperature. With a Ni adhesion layer, the resonance peak increased and blue-shifted due to improvement of metal quality without changing the sizes of nanostructures, while without the adhesion layer, the resonance wavelength can be tuned over a wider wavelength range by intentionally reducing the size of nanostructures through annealing. For Ag nanodisks with the adhesive layer, the plasmon resonance wavelength was blue-shifted due to the size reduction of nanodisks through thermal annealing. Full-color tuning of plasmonic resonance should be possible by controlling the diameter and height of Ag nanodisks under appropriate temperature conditions of heat treatment.

All-Dielectric Resonant Metasurfaces with a Strong Toroidal Response

We demonstrate how to create all-dielectric metasurfaces with a strong toroidal response by arranging two types of nanodisks into asymmetric quadrumer clusters. We demonstrate that a strong axial toroidal response of the metasurface is related to conditions of the trapped (dark) mode that is excited due the symmetry breaking in the cluster. We study the correlation between the toroidal response and asymmetry in the metasurface and nanocluster geometries, which appears from the different diameters of nanodisks or notches introduced into the nanodisks.

Plasmon enhancement of optical absorption in ultra-thin film solar cells by rear located aluminum nanodisk arrays

In this work, in order to enhance the light absorption in one micron thick crystalline silicon solar cells, a back reflecting and rear located plasmonic nanodisk scheme is proposed. We investigate the scattering properties of aluminum nanostructures located at the back side and optimize them for enhancing absorption in the silicon layer by using finite difference time domain simulations. The results indicate that the period and diameters of nanodisks, thickness of spacer layer have a strong impact on short circuit current enhancements. The optimized Al nanoparticle arrays embedded in rear located SiO2 layer enhance Jsc with an increase of 47% from the non-plasmonic case of 18.9 to 27.8 mA/cm2 when comparing with a typical stack with a planar aluminum back reflector and a back reflector with plasmonic nanoparticles. This finding could lead to improved light trapping within a thin silicon solar cell device.

Spontaneous nucleation and topological stabilization of skyrmions in magnetic nanodisks with the interfacial Dzyaloshinskii–Moriya interaction

One of the major societal challenges is reducing the power consumption of information technology (IT) devices and numerous data centers. Distinct from the current approaches based on switching of magnetic single-domain nanostructures or on movement of domain walls under high currents, an original magnetic skyrmion technology offers ultra-low power, fast, high-density, and scalable spintronic devices, including non-volatile random access memory. Using data-driven micromagnetic simulations, we demonstrate the possibility of spontaneous nucleation and stabilization of different skyrmionic states, such as skyrmions, merons, and meron-like configurations, in heavy metal/ferromagnetic nanodisks with the interfacial Dzyaloshinskii–Moriya interaction (iDMI) as a result of quasi-static magnetization reversal only. Since iDMI is not easily modulated in real systems, we show that skyrmion stabilization is easily achievable by manipulating magnetic anisotropy, saturation magnetization, and the diameters of nanodisks. The state diagrams, presented in terms of the topological charge, allow to explicitly distinguish the intermediate states between skyrmions and merons and can be used for developing a skyrmionic medium, which has been recently proposed to be a building block for future spin-orbitronic devices.

Omnidirectional polarization-insensitive tunable absorption in graphene metamaterial of nanodisk structure

Tunable absorption based on graphene metamaterial with nanodisk structure at near-infrared frequency was investigated using the finite difference time domain method. The absorption of the nanodisk structure which consisting of Au-MgF2-graphene-Au-polyimide (from bottom to top) can be tuned by the chemical potential of graphene at certain diameter of nanodisk. The permittivity of graphene is discussed with different chemical potential to obtain tunable absorption. It is shown that the increased value of the chemical potential of graphene can lead to blue-shifted of the absorption peaks and the values decreased. Moreover, dual-band and triple-band absorption can be achieved for resonance frequencies at normal incidence. Compared with diameter of nanodisks, the multilayer structure shows multi-band absorber, and an omnidirectional absorption at 195.25 THz is insensitive to TE/TM polarization. This omnidirectional polarization insensitive absorption may be applied by optical communications such as optical absorber, near infrared stealth, and filter.

Angle-insensitive plasmonic color filters with randomly distributed silver nanodisks.

Plasmonic color filters inherently suffer from angular sensitiveness, which hinder them from practical applications. Here, we present a plasmonic subtractive color filter incorporating two-dimensional randomly distributed silver nanodisks on top of a glass substrate. Due to the elimination of structural periodicity, the proposed plasmonic color filter works via localized surface plasmon resonances (LSPRs) and thus enables excellent angle-insensitive (up to 60°) performance. In addition, uncoupled LSPRs between nanodisks guarantee stability and reproducibility of the color filter. Finally, a palette of colors across the visible region was obtained with the proposed color filters by simply varying the diameter of nanodisks, exhibiting a promising and robust applicability in digital imaging and sensing industries.

Large-scale uniform Au nanodisk arrays fabricated via x-ray interference lithography for reproducible and sensitive SERS substrate

Large-scale Au nanodisk arrays on Si substrate are successfully fabricated via x-ray interference lithography and followed by electron-beam vapor deposition. The Au nanodisk arrays exhibit a significant, uniform, and reproducible surface enhancement on Raman scattering signal, which enables the detection of R6G as low as 10−8 M with an enhancement factor of 106. Importantly, the Au nanodisk arrays SERS-active substrates with uniformly high sensitivity also have high reproducibility and stability. The diameters of the nanodisks and the inter-disk distance can be simply optimized to obtain high enhancement in Raman signal by varying exposure time and development time in XIL process. The electric fields of the Au nanodisks with various diameters and inter-disk distance simulated by the finite difference time domain (FDTD) techniques further confirm that the Raman signal enhancement of Au nanodisks is determined by the diameters of nanodisks and the inter-disk distance of nanodisks. The Au/Ag double-layer bimetal nanodisk arrays are also fabricated which show a significant increase in the Raman signal enhancement than that of the Au nanodisk arrays. XIL nanofabrication appears to be a feasible approach to prepare uniform and reproducible SERS-active substrates with high sensitivity for practical SERS applications.

Surface Plasmon Resonance in Periodic Hexagonal Lattice Arrays of Silver Nanodisks

The surface plasmon resonance (SPR) of periodic hexagonal lattice arrays of silver nano‐disks positioned on glass slides is studied using finite‐difference time domain (FDTD) simulations. We investigate numerically the influence of diameter of nano‐disks and the gap between nano‐disks on SPR transmission spectra and electric field enhancement. We find a strong dependence of resonance wavelength on diameter of the nanodisks. With increasing the gap, electric field enhancement factor could significantly increase and reach a maximum value, which indicates that a special long‐range interaction plays an important role. This study is useful for optical modulation applied in near or far field optics, sensing and data storage, and solar cell.