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Enhancement of the Electric Field and Diminishment of the Group Velocity of Light in Dielectric Multilayer Systems: A General Description
摘要： We present analytical formulae for light propagation through a multilayer of dielectric media as a function of the “total charge” and the “accumulated charge” that we propose by the transfer-matrix method. We redefine the concept of the total charge introduced by Liu et al. [J. Phys. Condens. Matter. 29, 455303 (2017)] and newly define the accumulated charge to determine the magnitude of electric field inside the multilayers analytically. In addition, we derive an analytical expression for the group velocity of light in each layer. The purpose of this work is to predict which kind of sequence would provide the strongest amplification of the electric field inside the multilayer as well as to find the sequence that gives the lowest group velocity. We find that the symmetric alternating sequence gives the best amplification of the electric field and the lowest mean group velocity compared with the other sequences.
关键词： dielectric multilayer systems,group velocity,transfer-matrix method,electric field enhancement
更新于2025-09-09 09:28:46
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Orientation dependence of electric field induced phase transitions in lead-free (Na <sub/>0.5</sub> Bi <sub/>0.5</sub> )TiO <sub/>3</sub> -based single crystals
摘要： The orientation dependence of the electric field induced strain and phase transitions in 0.92(Na0.5Bi0.5)TiO3-0.06BaTiO3-0.02(K0.5Na0.5)NbO3 (NBT-6BT-2KNN) single crystals has been investigated. The evolution of Raman spectra with electric field reveals that a tetragonal ferroelectric phase is initially induced at E=14kV/cm and completed above E=25kV/cm for [001] oriented single crystals. When the electric field is applied along [111] direction, a partial phase transition from pseudocubic to rhombohedral structure is triggered at E=19kV/cm, which is higher than that for inducing tetragonal ferroelectric phase along [001] direction. Both field-induced phase structures and stability of NBT-6BT-2KNN single crystal are strongly associated with the crystallographic orientations. These results provide a better understanding to the field-induced macroscopic strain in lead-free NBT-based ferroelectrics.
关键词： X-ray diffraction,lead-free ferroelectrics,electric field induced phase transitions,Raman spectroscopy,NBT-based single crystals
更新于2025-09-09 09:28:46
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Analysis of AlGaN/GaN HEMT using discrete field plate technique for high power and high frequency applications
摘要： In this paper, the RF and DC characteristics of AlGaN/GaN High electron mobility transistor is analysed using discrete field plate technique. Surprisingly, it reduces the device parasitic capacitance exhibiting very low CGS and CGD of 5.8 ×10-13 F/mm and 4.2×10-13 F/mm respectively to improve the cut off frequency (fT) from 17.5 GHz to 20 GHz. The discrete field plate suppresses the maximum electric field between gate and drain region to achieve the high breakdown voltage of 330 V. The maximum transconductance (gm) achieved is 275 mS/mm, ensuring the better DC operation of the device. The simulated results clearly show that, the discrete field plate HEMTs are superior in performance over conventional GaN FP- HEMTs for future high frequency and high power applications.
关键词： cut off frequency,electric field,breakdown voltage,field plate,GaN HEMT
更新于2025-09-04 15:30:14
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Structure stability of few-layer graphene under high electric field
摘要： The stability of material structure is the key factor to determine its service capacity and lifetime. The structure evolution of vertical few-layer graphene (FLG) under high electric field was directly observed in situ TEM. The structure stability of FLG depends on its crystallinity and edge morphology. The vertical FLG without pinhole defects can sustain an electrostatic field beyond 58.5 V/nm. The vertical FLG with pinhole defects disintegrated from top to bottom due to field evaporation and the critical electrostatic field weaken to 17.4 V/nm. The vertical FLG with curly layer perpendicular to the electric field stretched and slid at the edge due to the layer sliding and the critical fracture electrostatic field of it was low to 7.5 V/nm which is an order of magnitudes small than that of the curly layer parallel to the electrostatic field of 24.7 V/nm. Those results were the first direct observation of the nano-structure evolution of FLG under high electric field. It helps to understand the deterioration mechanism of FLG under high electric field in free space and provides guidance for the high electric field applications such as field electron emitter and scanning tunneling microscopy.
关键词： Few-layer graphene,Layer sliding,Field evaporation,Structure stability,High electric field
更新于2025-09-04 15:30:14
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[IEEE 2018 Photonics North (PN) - Montreal, QC, Canada (2018.6.5-2018.6.7)] 2018 Photonics North (PN) - Double Hot-Spot Dual-Polarization Chand-Bali Nanoantenna for NIR Detection Applications
摘要： In this work, we introduce a novel design of a gold nanoantenna array. The nanoantenna consists of two elliptical patches. A vertical oval coincides with the minor axis of the horizontal oval. An elliptical aperture etched out from the horizontal one resulting in our Chand-Bali shaped nanoantenna. The geometrical dimensions are properly selected such that two symmetrical small gaps are created. The electric field intensity has a significant enhancement in these two gaps at the same resonance frequency within the near-infrared (NIR) regime for both orthogonal polarizations. The new design offers an improved performance for IR detection and harvesting applications.
关键词： energy harvesting,nanoantenna,NIR,dual polarization,electric field enhancement
更新于2025-09-04 15:30:14
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Enhancement of channel electric field in AlGaN/GaN multi-nanochannel high electron mobility transistors
摘要： We studied the drain current properties of an AlGaN/GaN multi-nano-channel (MNC) high electron mobility transistor (HEMT) fabricated on a sapphire substrate. We observed that the MNC HEMT exhibits the currents almost equal to those in the conventional planar device grown on the same chip. This result was unexpected since the actual gate width on the AlGaN surface in the case of MNC HEMT was only 20% of that for the planar device. In order to explain our experimental results, we performed a three dimensional (3D) simulation of the planar and MNC HEMTs using the TCAD Sentaurus software. Especially, we calculated the transfer characteristics of the MNC HEMT with a different nanochannel width and compared them with experimental data. The simulation results exhibited a good agreement with experimental ones. On this basis, we showed that the unusual behavior of the current in the MNC HEMT results from the enhancement of the effective electron velocity (ve) under the gate. In particular, we found that ve for the MNC HEMT was about 2.5 times higher than for the conventional HEMT, i.e., 2:44 (cid:1) 107 cm/s, which is close to the peak saturation velocity in GaN (2:5 (cid:1) 107 cm/s). Finally, we showed that such a strong enhancement of ve in the MNC HEMT case is due to the formation of the high electric ?eld in the nanochannel. The results obtained in this work are not limited only to MNC structures but they should also be useful in understanding the electric ?eld and electron velocity distribution in other AlGaN/GaN HEMTs with 3D nanochannels such as AlGaN/GaN FinFETs. Published by AIP Publishing.
关键词： high electron mobility transistor,electron velocity,electric field,AlGaN/GaN,multi-nano-channel
更新于2025-09-04 15:30:14
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Visible-light-responsive bismuth oxybromide/graphite-like C3N4 hybrid material and its application in photocatalysis via internal electric field
摘要： In this work, we propose a facile route to obtain BiOBr/ graphite-like C3N4 hybrid material, which was constructed by in situ depositing BiOBr onto the surface of g-C3N4 as a template via self-assembly procedure at room temperature. This method describes the use of g-C3N4/BiOBr nanocomposite for the superior photocatalytic performances under visible light excitation (λ > 420 nm). The crystalline phase, morphology, textile structure and components of the samples were studied by several tools such as X-ray diffraction, transmission electron microscopy, N2 adsorption–desorption, energy dispersive X-ray spectrum, Fourier transform infrared spectroscopy and Raman spectroscopy. The optical, photoelectrochemical properties and band structure were measured by ultraviolet–visible diffuse reflectance spectroscopy, steady-state photoluminescence spectra, photocurrent response analysis, electrochemical impedance spectra and valence-band X-ray photoelectron spectroscopy techniques, respectively. In addition, the catalytic activities of the hetero-structural material were broadly investigated and compared with single BiOBr or g-C3N4 alone in the same reaction. The as-obtained BiOBr/g-C3N4 composite showed distinctive advantages over BiOBr alone and universality for various substrate, i.e., dichloronaphthol degradation and reduction efficiency of Cr (VI) over BiOBr/g-C3N4 was increased by up to 3 and 2.5 times, respectively. The enhanced photocatalytic activity of the as-prepared BiOBr/g-C3N4 complex was mainly contributed to the effective charge transfer, which can further cause the establishment of the internal electric field in the interface between BiOBr and g-C3N4 to boost the space charge separation. This work gives a new route for designing high efficient semiconductor hybrid photocatalyst with broad absorption region as well as quick charge separation.
关键词： Graphite-like C3N4,BiOBr,Self-assembly,Photoelectrochemical,Internal electric field
更新于2025-09-04 15:30:14
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Electric-field induced structural transition in vertical MoTe2- and Mo1–xWxTe2-based resistive memories
摘要： Transition metal dichalcogenides have attracted attention as potential building blocks for various electronic applications due to their atomically thin nature and polymorphism. Here, we report an electric-field-induced structural transition from a 2H semiconducting to a distorted transient structure (2Hd) and orthorhombic Td conducting phase in vertical 2H-MoTe2- and Mo1?xWxTe2-based resistive random access memory (RRAM) devices. RRAM programming voltages are tunable by the transition metal dichalcogenide thickness and show a distinctive trend of requiring lower electric fields for Mo1?xWxTe2 alloys versus MoTe2 compounds. Devices showed reproducible resistive switching within 10?ns between a high resistive state and a low resistive state. Moreover, using an Al2O3/MoTe2 stack, On/off current ratios of 106 with programming currents lower than 1?μA were achieved in a selectorless RRAM architecture. The sum of these findings demonstrates that controlled electrical state switching in two-dimensional materials is achievable and highlights the potential of transition metal dichalcogenides for memory applications.
关键词： Transition metal dichalcogenides,electric-field-induced structural transition,MoTe2,Mo1?xWxTe2,RRAM
更新于2025-09-04 15:30:14
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Band gap modulation of ZrX<sub>2</sub> (X = S, Se, Te) mono-layers under biaxial strain and transverse electric field and its lattice dynamic properties: A first principles study
摘要： The effect of strain on the electronic properties of mono-layers of Zirconium based dichalcogenides ZrX2 (X = S, Se, Te) was studied using density functional theory based first-principles calculations. The variation in band gap due to biaxial tensile as well as compressive strain was calculated in these mono-layers. The modulation in band gap on application of external electric field has also been studied and it is observed that it decreases monotonically on applying a transverse electric field. These mono-layers and their strained structure are found to be dynamically stable as observed from their phonon spectrum. The population analysis in these systems indicates that with decreasing strain the d-population of Zr atoms increases whereas the p-population of S, Se, Te atoms decreases.
关键词： Electric field,ZrTe2,Strain,Phonon,ZrSe2,Electronic properties,ZrS2
更新于2025-09-04 15:30:14
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Dependence of Modulation Transfer Function on Electric Field Intensity of Photo conductor and Mobility-lifetime Product of Carriers in Polycrystalline Mercuric Iodide Based Flat Panel X-Ray Detectors: A Quantitative Approach and Error Analysis
摘要： In this Paper, a simplified mathematical model for Modulation Transfer Function (MTF) of Polycrystalline Mercuric Iodide based flat panel x-ray detector is applied on three different published prototypes of Polycrystalline Mercuric Iodide. Our aim was to fit the curves generated by simulation of MTF model with the curves acquired from experimental data. The mobility-lifetime product for the best curve fitting was examined for each prototype. Percentage of fitting error has been estimated for each prototype. Finally, average absolute error has been calculated for all the incorporated prototypes. This study can be further extended to develop a generic empirical model for the Modulation Transfer Function of polycrystalline mercuric iodide based flat panel x-ray detectors.
关键词： Modulation Transfer Function,Mobility-Lifetime Product,Average Absolute Error,Error Analysis,Empirical Model,Electric Field Intensity
更新于2025-09-04 15:30:14