Electric Field Coupling Effect Research Articles

Fabricating and investigating a beveled mesa with a specific inclination angle to improve electrical and optical performances for GaN-based micro-light-emitting diodes.

In this Letter, beveled mesas for 30 × 30 µm2 GaN-based micro-light-emitting diodes (µLEDs) with different inclination angles are designed, fabricated, and measured. We find that µLED with a mesa inclination angle of 28° has the lowest internal quantum efficiency (IQE) and the highest injection current density at which the peak IQE is obtained. This is due to the increased quantum confined Stark effect (QCSE) at the mesa edge. The increased QCSE results from the strong electric field coupling effect. Instead of radiative recombination, more nonradiative recombination and leakage current will be generated in the sidewall regions. Besides, the smallest angle (28°) also produces the lowest light extraction efficiency (LEE), which arises from the optical loss caused by the sidewall reflection at the beveled surface sides. Therefore, the inclination angle for the beveled mesa has to be increased to 52° and 61° by using Ni and SiO2 as hard masks, respectively. Experimental and numerical results show that the external quantum efficiency (EQE) and the optical power can be enhanced for the fabricated devices. Meanwhile, the reduced surface recombination rate also decreases the leakage current.

Effects of electric field on vibrational resonances in Hindmarsh–Rose neuronal systems for signal detection

Changes in the concentration of charged ions in neurons can generate induced electric fields, which can further modulate cell membrane potential. In this paper, Fourier coefficients are used to investigate the effect of electric field on vibrational resonance for signal detection in a single neuron model and a bidirectionally coupled neuron model, respectively. The study found that the internal electric field weakens vibrational resonance by changing two factors, membrane potential and phase-locked mode, while the periodic external electric field of an appropriate frequency significantly enhances the vibrational resonance, suggesting that the external electric field may play a constructive role in the detection of weak signals in the brain and neuronal systems. Furthermore, when the coupling of two neurons is considered, the effect of the electric field on the vibrational resonance is similar to that of a single neuron. The paper also illustrates the effect of electric field coupling on vibrational resonance. This study may provide a new theoretical basis for understanding information encoding and transmission in neurons.

Broadband infrared emissivity of Ag@SiO2 nanoparticles due to coupled transverse EM modes

The extension of plasmonic spectra to the Mid-Infrared (MIR) spectral range (2 μm to 14 μm) of Silver coated Silica (Ag@SiO2) nanoparticles was discussed in this paper. Most of the previous findings in this regard, describe the intrinsic infrared response of individual Ag@SiO2 particles or dimer and less explanation is available about the effect of electric field coupling over infrared radiation. This work provides detailed analysis about the contribution in the infrared response from the coupling of transverse EM (Electric-Magnetic) modes between the particles in the dimer. The simulated data also suggests a strong dependence of infrared radiation on the coupling of transverse EM which will facilitate the researchers in future to prepare the paint of randomly distributed Ag@SiO2 nanoparticles for passive radiative cooling. A smooth extra thin shell of Ag were deposited over SiO2 nanoparticles successfully, by employing wet chemical method. The morphology, qualitative and quantitative analysis were performed by using Transmission Electron spectroscopy (TEM) and Energy Dispersive X-ray Spectroscopy (EDS) respectively. The emissivity of the particles was measured with the Fourier Transform Infrared (FTIR) Spectrometer. The IR response of Ag@SiO2 nanoparticles was simulated by employing the Finite Element Method (FEM) with the Microwave Studio in Computer Simulation Technology (CST) software. All the simulations and experimental results were found in agreement with slight difference between them. This slight difference has been explained in Modeling and Numerical analysis section.

Effects of electric field coupling on the circular dichroism of composite nanostructures

Chirality has substantial applications in the fields of medicine, biology, and physics. Previous studies of strong chiral responses mostly involved complex 3D plasmonic nanostructures. In this study, we demonstrate a planar plasmonic composite nanostructure to achieve large circular dichroism (CD) effect by tuning the coupling effect. By introducing a rectangular block to an L-shaped nanostructure, the resonance wavelength at different handed circular polarization incidences is separated. At the same time, the resonance of the composite nanostructure is observable for one circularly polarized light excitation but subdued for another circularly polarized light excitation, leading to a large CD effect. In addition, the CD effects of composite nanostructures are strongly dependent on the structural parameters. These results could provide a novel approach to tune resonance wavelengths and achieve larger CD effects.

Engineering of flexible granular Au nanocap ordered array and its surface enhanced Raman spectroscopy effect

Surface enhanced Raman spectroscopy (SERS) is a new and developing analytical technology in chemical and biological detection. However, traditional hard SERS substrates are struggling to meet the growing demand for flexible devices. In this work, we introduce a simple, cost-effective and large scale preparation route to form a flexible Au nanocap (AuNC) ordered array as SERS substrates via reactive ion etching (RIE) method and then Au deposition. We find RIE is an excellent method for nanoroughening the surface of polystyrene (PS) spheres. Such flexible SERS substrates exhibit high sensitivity and uniformity for detecting organic molecules. The finite-difference time-domain simulation results revealed that a strong electric field coupling effect existed not only in the gap site between the Au nanoparticles (AuNPs), but also in the connection position between the AuNCs and the single AuNP. This study not only offers a novel way for nanoroughening of PS spheres, but also acquires flexible and cheap SERS substrates for quick and sensitive detection of organic molecules.

Sensitivity enhanced D-type large-core fiber SPR sensor based on Gold nanoparticle/Au film co-modification

A D-type large core optical fiber sensor with high sensitivity and good stability based on the coupling of gold nanoparticles and Au film was proposed and demonstrated by simulation and experiments. The proposed sensor is numerically simulated based on the finite element method. The simulation shows that the electric field intensity of the gap coupling between gold nanoparticles and Au film is 4–5 times higher than that of Au film, and the electric field intensity on the surface of gold nanoparticles is twice as strong as that on the surface of Au films. The electric field coupling effect between the Au film surface plasmon resonance (SPR) and the gold nanoparticle localized surface plasmon resonance (LSPR) can improve the refractive index sensitivity of the sensor. Experimental results show that the refractive index sensitivity of D-type optical fiber/Au film/gold nanoparticles sensor reaches 3074 nm/refraction index unit (RIU), which is 1.4 times that of D-type optical fiber/Au film sensor. SPR–LSPR coupling effect is a good method to improve the sensing performance of optical fiber sensors, especially for detecting the refractive index changes of surrounding media. Compared with existing similar biosensors, the designed biosensor has higher sensitivity and the sensor proposed in this paper has great application prospects in the field of biological detection.

Sensitivity-Enhanced Optical Fiber Biosensor Based on Coupling Effect Between SPR and LSPR

An optical fiber biosensor based on gold nanoparticles and protein A co-modified Au film coated photonic crystal fiber (Au-PCF) is proposed and demonstrated for human IgG detection. For the electric field coupling effect between surface plasmon resonance (SPR) of Au film and localized surface plasmon resonance (LSPR) of gold nanoparticles, the refractive index sensitivity can be enhanced significantly. Besides, goat anti-human IgG is immobilized by protein A modified on the gold nanoparticles surface to interact with human IgG. Protein A can specifically bind the Fc region of the antibodies and has a high degree of orientation for capturing antibodies. Experimental results indicate that the refractive index sensitivity of Au-PCF sensor modified gold nanoparticles reaches 3915 nm/RIU, which is about 1.6 times higher than the Au-PCF sensor without gold nanoparticles modified. The lowest detection limit of human IgG based on gold nanoparticles and protein A co-modified Au-PCF sensor is 37 ng/mL, which is about 2.4 times and 6.3 times lower than gold nanoparticles-Au-PCF sensor and Au-PCF sensor, respectively. Such a sensitivity enhanced optical fiber biosensor based on SPR-LSPR coupling effect has potential application in clinical disease diagnosis and immunoassays.

Terahertz multiband ultrahigh index metamaterials by bilayer metallic grating structure

One-dimensional metallic grating structure was proposed to realize high refractive index metamaterial in the terahertz region. By drastically increasing the effective permittivity by means of intense capacitive coupling and reducing the diamagnetic effect using a thin metallic thickness, a peak refractive index of 15.81 at the resonant frequency in embedded metallic grating can be obtained. Multiband high refractive index metamaterial can be realized by double symmetric metallic grating and asymmetric grating structure. For asymmetric grating metamaterial structure, two separate transmission peaks appear and result in two separate high refractive index. Interestingly, a near zero refractive index metamaterial can be obtained by the introduction of double asymmetric design. It was found that our designed ultrahigh refractive index metamaterials depend on the electric field coupling effect and the magnetic field diamagnetic response.

Broadband polarization-independent two-dimensionally isotropic ultrahigh index metamaterials

By drastically decreasing the diamagnetic effect with a thin window type structure in the unit cell and increasing the effective permittivity through strong capacitive coupling, we report a window-type broadband isotropic two-dimensional metamaterial with extremely high refractive index in the terahertz region. The designed peak index of refraction of near 18.22 at about 1.15 THz is predicted. In the experiment, we fabricated a “window” type structural metamaterial, and the measured transmission was compared with the results of the simulation. The effective refractive index for the prepared metamaterial was extracted by S-parameter extraction method. It is found that ultrahigh refractive index metamaterials depend on the electric field coupling effect, the magnetic field diamagnetic response, and the geometric parameters in the unit cell. Higher resonant frequency makes it possible to utilize broader high refractive index with low loss and large transmission.

Improved electron injection and efficiency in blue organic light-emitting diodes using coupled electric field near cathode

Abstract In this paper, we report high-performance blue organic light-emitting diodes (OLEDs) based on evaporated silver nanoclusters (SNCs) located near the aluminum cathode. We investigate the influence of localized surface plasmon resonance (LSPR) and trapping effects of SNCs on the performances of blue OLEDs depending on the size, distribution, and location of the SNCs. The research results reveal when the SNCs are located in the electron transporting layer, the serious trapping effect would cause reduced current density and efficiency of our blue OLEDs. Fortunately, when the SNCs are close to the cathode, owing to the electric field coupling effect between the LSPR of SNCs and the surface polarization of aluminum cathode, the resonant electric field is concentrated near the cathode, thereby enhancing the electron injection. The balanced carrier injection and transport processes improve the performance of blue OLEDs. The optimized device with SNCs located 2 nm away from the aluminum cathode achieves the highest current efficiency of 40.7 cd/A, enhancing by 15% compared to the control device without SNCs.

Optical Properties of Thin Gold Nanoshell Arrays and Their Application as NIR SERS Substrate

The metallic hollow-core nanoshell arrays were fabricated by depositing relatively thin gold films onto a cleaned silicon support covered with a close-packed monolayer of 200 nm diameter polystyrene spheres and then removing the spheres. The relationship between their morphologies and optical properties was discussed. Then, the surface enhanced Raman scattering signals of 4-aminothiophenol (4-ATP) molecules adsorbed on the nanoshell arrays were obtained with the excitation wavelength of 785 nm and 1064nm, respectively. The results show that the localized surface plasmon resonance wavelength of gold nanoshell arrays can be precisely tuned over a wide range from visible region to infrared region by controlling the shell thickness of the nanoshell arrays, as the shell thickness increases, the resonance wavelength red shifts and the spectrum width broadens due to the electric field coupling effect among the nanoshell particles, the surface enhanced Raman scattering signals can be obtained obviously at two different infrared wavelengths of 785nm and 1064nm, indicating that the fabricated nanoshell arrays can be used as the potential low-cost surface enhanced Raman scattering substrates.

Manipulation of dual band ultrahigh index metamaterials in the terahertz region.

By drastically decreasing the diamagnetic effect with a thin metallic structure in the unit cell and increasing the effective permittivity through strong capacitive coupling, we designed the crossed I-shaped metallic patches metamaterial with an extremely high refractive index in the dual band terahertz region. The peak index of refraction of near 80 at about 0.75THz is predicted, along with another peak index of about 25 at 2.85THz. Based on the careful analysis of the high index on the dependence of the electric field coupling effect, the magnetic field diamagnetic response, and the geometric parameters in the unit cell, it is found that both of the high index bands respectively correspond to different components in the metamaterial structure. To realize a higher effective refractive index for the second band as well as for the first one, we proposed the triple I-shaped metallic metamaterial structure.

Large room-temperature electrocaloric effect in lead-free BaHfxTi1−xO3 ceramics under low electric field

Ferroelectrics are promising candidate materials for electrocaloric refrigeration. Materials with a large electrocaloric effect (ECE) near room temperature and a broad working temperature range are getting closer to practical applications. However, the enhanced ECE is always achieved under high electric field, which limits their wide cooling applications. In this paper, the phase diagram of lead-free BaHfxTi1−xO3 (BHT) ferroelectric ceramics was established. A large ECE under relatively low electric field (ΔE = 10 kV/cm) is firstly reported in BHT ferroelectric ceramics. The direct temperature change (ΔT = 0.35 °C under 10 kV/cm) in BHT ceramics is comparable with those reported in the literature under high electric fields. Meanwhile, the electrocaloric efficiency (ΔT/ΔE = 0.35 K mm kV−1 under 10 kV/cm) is thirteen percent higher than the best value reported previously under high electric field (ΔE = 145 kV/cm). We demonstrate that the ECE can be greatly enhanced by tuning the composition of the lead-free BHT ceramics to its first-order phase transition (FPT), invariant critical point (ICP) or diffuse phase transition (DPT). It is shown that the enhancement in ECE is strongly dependent on the nature of structural phase transition and electric field coupling effect, which has been confirmed by both the indirect and direct ECE measurements. A phenomenological explanation based on Landau model was also proposed to understand this phenomenon. Our findings in this work may provide a better understanding and design methodology for developing more practically useful electrocaloric materials.

Design, fabrication and application of an SOI-based resonant electric field microsensor with coplanar comb-shaped electrodes

This paper presents a highly sensitive resonant electric field microsensor based on silicon on insulator (SOI) technology. To improve the electric field coupling effect, the microsensor uses coplanar shutter electrodes and sense electrodes. To obtain higher conversion gain, both electrodes adopt novel comb-shaped structures. A finite element method (FEM) was used to simulate and optimize the structures of the comb-shaped electrodes. The sensitivity model of the microsensor was analyzed by the conversion gain of the vibration-amplitude-to-charge variation. The resolution of the microsensor is approximately 40 V m−1 with an uncertainty of 1% for the dc field, while the resolution is better than 10 V m−1 for the 50 Hz ac field. The microsensors were packaged and assembled to form an electric field probe to measure the atmospheric electric field. The test results showed that the probe precisely detected the occurrence of thunderstorms, and the plotted data agreed well with those of the conventional electric field mill.

Co-Integration of Nano-Scale Vertical- and Horizontal-Channel Metal-Oxide-Semiconductor Field-Effect Transistors for Low Power CMOS Technology

In order to extend the conventional low power Si CMOS technology beyond the 20-nm node without SOI substrates, we propose a novel co-integration scheme to build horizontal- and vertical-channel MOSFETs together and verify the idea using TCAD simulations. From the fabrication viewpoint, it is highlighted that this scheme provides additional vertical devices with good scalability by adding a few steps to the conventional CMOS process flow for fin formation. In addition, the benefits of the co-integrated vertical devices are investigated using a TCAD device simulation. From this study, it is confirmed that the vertical device shows improved off-current control and a larger drive current when the body dimension is less than 20 nm, due to the electric field coupling effect at the double-gated channel. Finally, the benefits from the circuit design viewpoint, such as the larger midpoint gain and beta and lower power consumption, are confirmed by the mixed-mode circuit simulation study.

Effects of incident polarization and electric field coupling on the surface plasmon properties of square hollow Ag nanostructures

Square hollow nanostructure can induce a large-area enhanced electric field at the main plasmon peak. Therefore, it can be used as a substrate for the surface enhanced Raman scattering. The effects of the incident polarization on the extinction spectrum and the electric field distribution of the square Ag nanostructure are studied by the discrete dipole approximation method. The results show that the plasmon peaks do not shift with the variation of incident polarization. However, the electric field distribution is strongly dependent on the direction of incident polarization. Additionally, the effect of the electric field coupling between adjacent square Ag nanostructures on the plasmon mode is also studied. It is found that the plasmon resonance can be tuned by varying the separation between adjacent squares. These results could be used to guide the preparation of such closed nanostructures for specific plasmonic applications.

Triaxial cable designs with optimum braided shields

An investigation into the shielding effectiveness of triaxial cables employing wire shields, with optimum braid constructions, is described. Several triaxial configurations with different braid designs, for inner and outer cables, were simulated. It is shown that crosstalk performances of the triaxial cables are affected by both absolute values and polarities of the surface transfer impedances of the shields. The effect of electric field coupling, on the overall crosstalk within the triaxial system, has also been studied in both frequency and time domains. For triaxial cables with shorted braids, the effects of electric field coupling are limited to high frequencies and their effects at low frequencies are small. >

Screening efficiency of triaxial cables with optimum braided shields

An investigation into the shielding effectiveness of triaxial cables employing wire shields with optimum braid constructions is described. Several triaxial configurations with different braid designs for inner and outer cables were simulated. It is shown that crosstalk performance of the triaxial cables are affected by both absolute values and polarities of the surface transfer impedances of the shields. The effect of electric field coupling on the overall crosstalk within the triaxial system has also been studied in both frequency and time domains. For triaxial cables with shorted braids, the effects of electric field coupling are limited to high frequencies, and their effects at low frequencies are small.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>