Local Field Enhancement Effect Research Articles

Nanophotonic Crescent Moon Structures with Sharp Edge for Ultrasensitive Biomolecular Detection by Local Electromagnetic Field Enhancement Effect

We present novel gold nanophotonic crescent moon structures with a sub-10 nm sharp edge, which can enhance local electromagnetic field at the edge area. The formation of unconventional nanophotonic crescent moon structure is accomplished by using a sacrificial nanosphere template and conventional thin film deposition method, which allows an effective batch nanofabrication and precise controls of nanostructure shapes. Unique multiple scattering peaks are observed in a single gold nanocrescent moon with dark-field white light illumination. A 785 nm near-infrared (NIR) diode laser was used as the excitation source to induce the amplified scattering field on the sharp edge of the single gold nanocrescent moon. The Raman scattering spectrum of Rhodamine 6G molecules adsorbed on the single gold nanocrescent moon are characterized, and the Raman enhancement factor of single gold nanocrescent moon is estimated larger than 10(10), which suggests the potential applications of gold nanocrescent moons in ultrasensitive biomolecular detection and cellular imaging using surface enhanced Raman spectroscopy.

Effect of tungsten implantation on electron field emission properties of ion-beam-synthesized SiC layers

The effect of tungsten implantation on the electron field emission (FE) properties of ion-beam-synthesized (IBS) SiC/Si heterostructures was studied and correlated to their microstructures and surface morphology. The turn-on field of the IBS SiC layers is improved from 25 to 14 V/μm after W implantation and is further decreased to 10 V/μm after thermal annealing at 1200 °C for 1 h. The improvements in FE properties after W implantation can be attributed to the formation of WC as well as two types of local field enhancement mechanisms. In the as-implanted sample, the local field enhancement effect is attributed to electrical inhomogeneity due to the formation of conducting WC nanoclusters embedded in the SiC layers. In the annealed samples, the dominated field enhancement is attributed to a surface morphology effect due to the formation of small protrusion structures at the surface.

Nanometer scale-electrochromic modification of NiO films using a novel technique of scanning near-field optical microscopy

Nanometer-scale observation and modification of NiO films were performed using a novel technique for scanning near-field optical microscopy (SNOM) combined with a current-sensing function. The novel SNOM was newly developed in order to investigate not only local optical distributions but also local electrical properties of EC materials. In order to detect optical and electrical properties at a local point on the material surface, a cantilever-type metal probe was fabricated. The near-field optical properties could be observed using the local field enhancement effect generated at the edge of the metal probe under p-polarized laser illumination. In regard to electrical observation, the current signal could be observed using the metal probe connected to a highly sensitive current amplifier. The surface topography, optical distribution and current image of the colored electrochromic (EC) material of NiO films were observed simultaneously using the current-sensing SNOM. Furthermore, nanometer-scale EC modification of local bleaching could be performed using the current-sensing SNOM. The current-sensing SNOM opens up new fields of EC materials in nanometer-scale optelectronic applications.

Current-sensing scanning near-field optical microscopy using a metal probe for nanometre-scale observation of electrochromic films.

A novel technique for scanning near-field optical microscopy capable of point-contact current-sensing was developed in order to investigate the nanometre-scale optical and electrical properties of electrochromic materials. An apertureless bent-metal probe was fabricated in order to detect optical and current signals at a local point on the electrochromic films. The near-field optical properties could be observed using the local field enhancement effect generated at the edge of the metal probe under p-polarized laser illumination. With regard to electrical properties, current signal could be detected with the metal probe connected to a high-sensitive current amplifier. Using the current-sensing scanning near-field optical microscopy, the surface topography, optical and current images of coloured WO3 thin films were observed simultaneously. Furthermore, nanometre-scale electrochromic modification of local bleaching could be performed using the current-sensing scanning near-field optical microscopy. The current-sensing scanning near-field optical microscopy has potential use in various fields of nanometre-scale optoelectronics.

Origins of field enhancement in electron field emission from ion beam synthesized SiC layers

SiC layers were synthesized by high-dose carbon implantation into silicon. Their electron field emission properties were studied and correlated with results from atomic force microscopy (AFM) and conducting AFM measurements. It is clearly demonstrated that there are two types of field enhancement mechanisms responsible for the improvement of the electron field emission properties of these ion beam synthesized SiC layers. In the as-implanted samples, the local field enhancement effect is attributed to electrical inhomogeneity due to the existence of small conducting graphitic clusters embedded in the layer. On the other hand, in the annealed samples, the dominant field enhancement mechanism is attributed to a surface morphology effect due to the formation of small protrusion structures at the surface.

Silver as a sensitizer for erbium

The photoluminescence of Er3+in borosilicate glass is strongly enhanced by the presence of silver. Samples prepared by a combination of erbium ion implantation and Na+↔Ag+ ion exchange show an increase of the Er3+excitation efficiency of up to a factor 70 when excited at 488 nm. Excitation of Er3+ is possible over a broad wavelength range in the near ultraviolet and visible. Our data suggest that absorption of light occurs at a silver ion/atom pair or similar defect, followed by energy transfer to Er3+. We can exclude that silver nanocrystals are part of the dominant excitation mechanism, neither via local field enhancement effects due to their surface plasmon resonance nor via absorption and subsequent energy transfer to Er3+.

Near-Field Probing Surface Plasmon Enhancement Effect on Two-Photon Emission

A photon scanning tunneling microscope is employed to probe the surface-plasmon-induced local field enhancement effect on two-photon fluorescence from organic nanoparticles adsorbed on silver surface. A size dependence of fluorescence enhancement and photodecomposition is observed, which results from the competition between the surface-plasmon-enhanced two-photon fluorescence and the nonradiative energy transfer from the excited dye molecules to the silver surface.

Local field enhancement effects for nanostructuring of surfaces

We report on a method that allows the nanostructuring of surfaces with intense laser pulses. For this purpose isolated polystyrene spheres with diameters in the order of the laser wavelength were deposited on a silicon or glass surface. Illumination with short and ultrashort laser pulses produced holes underneath these particles. Calculations of the field near the particles make clear that geometrical optics, that is, focusing by a spherical lens, as well as near-field effects, contribute to the size and shape of these holes. This technique can be utilized for the parallel structuring of large surface areas with a single laser shot.

Recent developments in the preparation and properties of nanometer-size spherical and platelet-shaped particles and composite particles

Abstract By using self-assembly molecules as a template, nanometer-sized plate-like metal oxide and semiconductor particles can be obtained by confined growth inside the lamellar bilayers of microemulsion systems. It was found that a strong chemical affinity between the metal salt and the polar head group of amphiphilic molecules and the anisotropic structure of microemulsion systems play a premier role in the anisotropic growth. Nanometer-sized composite particles (nano-composites) with a core-shell structure have been prepared by arrested precipitation of metal or semiconductor clusters in reverse micelles, followed by hydrolysis and condensation of organometallic precursors in the microemulsion matrices. Temporally discrete nucleation and growth at elevated temperature (70 °C) give the resulting particles a narrow size distribution and defined crystallinity. Both the size of the core particles and the thickness of the coating layers can be varied by controlling processing parameters such as the ratio of water to surfactant and the ratio of water to organometallic precursors. By controlling the pH conditions and aging temperatures, a transparent gel composing the nanometer-sized inorganic clusters has been obtained. Optical properties of nanometer-sized composite particles are reviewed. For silver metal clusters and nano-composites, the shift of the absorption peak at the surface-plasmon resonance frequency due to the classical limited mean-free path of the conduction electrons or quantum size effects has been observed. The enhanced third-order non-linear susceptibility of the silver nano-composites results from the local-field enhancement and size effects, which has been experimentally demonstrated by the optical phase-conjugation technique.