Исследование диэлектрических функций слоя наночастиц Ag на кремнии с помощью спектроэллипсометрии и спектрофотометрии

An investigation of the optical characteristics of a layer of Ag nanoparticles deposited from an AgNO3 solution on the surface of single-crystal Si is presented. The measurements were carried out using spectroscopic ellipsometry and spectrophotometry at the same tilt angle and sample probe location in a wide spectral range from 200 to 1700 nm. From the obtained experimental data, the parameters of the Drude-Lorentz model and the complex dielectric function were determined, which was compared with the pseudo-dielectric function. Both dependences revealed resonances of a bulk plasmon near the energy E = 3.8 eV, while a localized plasmon was detected in the pseudo-dielectric function at E = 1.65 eV, and in the dielectric function at E = 1.84 eV.

Bulk plasmon polariton in hyperbolic metamaterials excited by multilayer nanoparticles for surface-enhanced Raman scattering (SERS) sensing

The capability to support large wave vector bulk plasmon polariton (BPP) waves enables the application of hyperbolic metamaterials (HMMs) in sensing. However, there is a challenge arising from the excitation of BPP, and the highly confined polarization waves are unable to meet the requirements of practical application. In this study, an HMM/bilayer silver nanoparticles (Ag NPs) platform is proposed that allows the excitation and utilization of BPP for use as a surface-enhanced Raman scattering (SERS) substrate. According to the research results, the bilayer Ag NPs provide stronger plasmonic property and act as a light-matter coupler, so as to generate a large wave vector of scattered light and excite the BPP within the HMM. Besides, Ag NPs provide the nano antenna structure, and decouple the BPP into localized surface plasmon (LSP) that can be used directly to excite the electric fields. In addition, HMM produces a modulating effect on the plasmon resonance peak, which makes it possible to overlap the spectrum of resonance peak with excitation wavelengths, thus leading to a strong absorption peak at the incident laser wavelength region. Experimentally, the platform was applied to achieve SERS detection for adenosine molecules with a concentration of 10−6 M. It is believed that this plasmonic platform has a potential of application in surface-enhanced spectroscopy.

Switchable Gratings for Ultracompact and Ultrahigh Modulation Depth Plasmonic Switches

Plasmonic interconnects present a compact platform for high modulation-depth optical switches. Conventional plasmonic switching approaches depend on modifying the dispersion of the surface plasmon polariton (SPP) wave at the metal/dielectric interface. Here, we introduce a novel scheme for ultracompact and high modulation depth (MD) plasmonic switching using a phase-change material-based switchable grating consisting of Antimony Trisulfide (Sb2S3). In its ON state, the switchable grating excites surface plasmon polaritons (SPP) and bulk plasmon polaritons (BPPs) in plasmonic films and hyperbolic metamaterials (HMMs), respectively. The SPP switch has a footprint of 23.1 µm2 and a MD of up to 40 dB. The BPP switch has a footprint of 13.12 µm2 and a MD of 29.7 dB. The BPP switch enjoys a broadband MD from 299–375 THz. Concurrently, we show that the same switchable grating on plasmonic film and on HMM is a reflection-based optical switch. Finally, we present a novel scheme for non-local control over the spontaneous emission rate and out-coupled power from emitters embedded in HMMs.

Plasmonic evolution of atomically size-selected Au clusters by electron energy loss spectrum

The plasmonic response of gold clusters with atom number (N) = 100–70000 is investigated using scanning transmission electron microscopy-electron energy loss spectroscopy. For decreasing N, the bulk plasmon remains unchanged above N = 887 but then disappears, while the surface plasmon firstly redshifts from 2.4 to 2.3 eV above N = 887 before blueshifting towards 2.6 eV down to N = 300 andfinally splitting into 3 fine features. The surface plasmon's excitation ratio is found to follow N^0.669, which is essentially R^2. An atomically-precise picture of evolution picture of plasmon physics is thus demonstrated according to 3 regimes: classical plasmon (N = 887–70000), quantum confinement corrected plasmon (N = 300–887) and molecule related plasmon (N < 300).

Исследование оптических и плазмонных особенностей в спектрах отражения слоев наночастиц серебра, осажденных из раствора AgNO-=SUB=-3-=/SUB=- на поверхности кремния

To interpret the spectra of reflectivity of Ag layers on a silicon substrate, an approach with the use of calculation of the reflection spectra Rcalc of a thin film with varying thickness are used, as a result of which the influence of the critical points of the c-Si substrate in the Brillouin zone and the formation of characteristics bulk Ag near the edge of interband transitions are studied. The Rcalc spectra were compared with experimental Rexp spectra of the Ag nanoparticles layers of various morphologies, measured at normal and oblique (45°) angles of incidence of light. For a layer with larger nanoparticles, the formation of a sharp dip in the Rexp spectrum, which practically coincides with the edge of the interband transitions of bulk Ag in UV range, is observed, as well as a wide dip in the Rexp spectrum with a minimum at λ = 382 nm demonstrates absorption maximum of localized plasmon resonance of Ag nanoparticles. For samples with less the size of particles, there is no dip due to the interband transitions in the Rexp spectra for both of incidence angles, since the deposited Ag nanoparticles did not form into a structure with the optical properties of bulk Ag, but the bulk plasmon resonance appeared at λ= 335 nm in the longitudinal mode at an oblique angle incident light.

Preparation of Graphene/ITO Nanorod Metamaterial/U-Bent-Annealing Fiber Sensor and DNA Biomolecule Detection

In this paper, a graphene/ITO nanorod metamaterial/U-bent-annealing (Gr/ITO-NM/U-bent-A)-based U-bent optical fiber local surface plasmon resonance (LSPR) sensor is presented and demonstrated for DNA detection. The proposed sensor, compared with other conventional sensors, exhibits higher sensitivity, lower cost, as well as better biological affinity and oxidize resistance. Besides, it has a structure of an original Indium Tin Oxides (ITO) nanocolumn array coated with graphene, allowing the sensor to exert significant bulk plasmon resonance effect. Moreover, for its discontinuous structure, a larger specific surface area is created to accommodate more biomolecules, thus maximizing the biological properties. The fabricated sensors exhibit great performance (690.7 nm/RIU) in alcohol solution testing. Furthermore, it also exhibits an excellent linear response (R2 = 0.998) to the target DNA with respective concentrations from 0.1 to 100 nM suggesting the promising medical applications of such sensors.