Showing papers by "Wen-Yan Yin published in 2018"
TL;DR: In this article, the authors proposed a reconfigurable toroidal circular dichroism of kirigami-based chiral metamaterials, whose electromagnetic functionalities can be switched between non-chiral and chiral states by stretching the predesigned split-ring resonator array.
Abstract: The ancient paper craft of kirigami has recently emerged as a potential tool for the design of functional materials. Inspired by the kirigami concept, we propose a class of kirigami-based metamaterials whose electromagnetic functionalities can be switched between nonchiral and chiral states by stretching the predesigned split-ring resonator array. Single-band, dual-band, and broadband circular polarizers with reconfigurable performance are experimentally demonstrated with maximum circular dichroism of 0.88, 0.94, and 0.92, respectively. The underlying mechanism is explained and calculated via detailed analysis of the excited multipoles, including the electric, magnetic, and toroidal dipoles and quadrupole. Our approach enables tailoring the electromagnetic functionalities in kirigami patterns and provides an alternate avenue for reconfigurable optical metadevices with exceptional mechanical properties. A new twist on the Japanese art of origami has helped researchers achieve dynamic optical polarization switching for applications including lasers and biosensors. Metamaterials, substances engineered to manipulate radiation in non-natural ways—bending light around objects to make them appear invisible, for example—are normally impossible to re-configure after being fabricated. Liqiao Jing from Zhejiang University in Hangzhou, China, and colleagues have overcome this limitation by depositing periodic arrays of copper rings onto thin, foldable polymer sheets. By introducing small cuts and then stretching the sheets, the team created buckled, 3D surfaces with different symmetries to the original flat film. The rearranged atoms in the new structures enabled filtering of circularly polarized light, an effect which could be expanded to broadband frequencies by stacking two folded films on top of one another. An approach towards kirigami metamaterials with reconfigurable toroidal circular dichroism is presented. Inspired by the kirigami concept, kirigami-based chiral metamaterials are proposed to switch the electromagnetic performance between non-chiral and chiral states. When transforming the 2D metasurface to 3D kirigami patterns, the resonant modes exhibit gradually enhanced chiroptical response, from single-band, dual-band to broad-band functionalities.
49 citations
TL;DR: It is shown that the time delay and temperature rise can be reduced by replacing the conventional diffusion barriers in the Cu/low-k interconnect with the graphene barriers.
Abstract: Due to its ultrathin feature, graphene has been recently proposed as diffusion barrier layer for Cu wires This paper is geared toward developing an equivalent single-conductor (ESC) transmission-line (TL) model for analysis of Cu-graphene interconnects, ie, Cu wires encapsulated with graphene barriers Based on the ESC TL model, electrical performances of Cu-graphene interconnects are examined and evaluated It is shown that the time delay and temperature rise can be reduced by replacing the conventional diffusion barriers in the Cu/low-k interconnect with the graphene barriers
32 citations
TL;DR: This metamaterial is proposed and experimentally demonstrated compact planar metadisks based on split ring resonators to support the toroidal LSSPs at microwave frequencies and it is experimentally demonstrating that the toroids resonance is very sensitive to the structure changes and the background medium.
Abstract: Localized spoof surface plasmons (LSSPs) have recently emerged as a new research frontier due to their unique properties and increasing applications. Despite the importance, most of the current researches only focus on electric/magnetic LSSPs. Very recent research has revealed that toroidal LSSPs, LSSPs modes with multipole toroidal moments, can be achieved at a point defect in a 2D groove metal array. However, this metamaterial shows the limitations of large volume and poor compatibility to photonic integrated circuits. To overcome the above challenges, here it is proposed and experimentally demonstrated compact planar metadisks based on split ring resonators to support the toroidal LSSPs at microwave frequencies. Additionally, it is experimentally demonstrated that the toroidal LSSPs resonance is very sensitive to the structure changes and the background medium. These might facilitate its utilization in the design and application of plasmonic deformation sensors and the refractive index sensors.
30 citations
TL;DR: The extended cavity model can provide a deep physical insight into the LC-based antenna and help to understand the differential operation of this frequency tunable circular-ring patch antenna.
Abstract: A differential probe-fed liquid crystal (LC)-based frequency tunable circular-ring patch antenna is presented. Besides, cavity model is extended to analyze the LC-based antenna for the differential operation. According to the cavity model, the permittivity and loss tangent of the LC are extracted from the measured differential reflection coefficients. Acceptable agreements among the measurement, simulation, and calculation for differential impedances, reflection coefficients, and radiation patterns are obtained and also validate the extraction method and model. More importantly, the extended cavity model can provide a deep physical insight into the LC-based antenna.
22 citations
TL;DR: In this article, the van der Waals stacking was used for the first experimental realization of purely two-dimensional-material-based hot electron transistor (2D-HET).
Abstract: In this letter, we report the first experimental realization of purely two-dimensional-material-based hot electron transistor (2D-HET) by the van der Waals stacking. We used ultra-thin graphene as the base, and WSe2 or ${h}$ -BN as the emitter-base or base-collector barriers. We quantitatively determined that the transport mechanism through the 2D barrier changes from the Fowler–Nordheim tunneling to the thermionic emission with the increase of temperature. In our 2D-HET, the dangling-bond-free 2D materials provide atomically sharp interfaces to suppress the hot electron scattering, which along with the optimization of the barriers, gives a relatively large collection efficiency of 99.95% and a relatively high current density of 233 A/cm2 in the family of graphene-base HETs.
21 citations
TL;DR: In this paper, an improved ultrawideband open-short de-embedding methodology is presented, which is a measurement-calculation hybrid method, and it is applied to active devices.
Abstract: This paper presents an improved ultrawideband open-short de-embedding methodology. In contrast to the conventional measurement-based open-short de-embedding method, the presented method is a measurement-calculation hybrid method. First, the open and short de-embedding structures are measured, and the corresponding scattering parameters are obtained. Based on this, lumped-parameter models of the open and short de-embedding structures are established. Then, the established models are modified to solve the over de-embedding problem. Finally, the modified de-embedding structure models are implemented in the scattering parameters of device test structures to achieve ultrawideband de-embedding. To verify the proposed de-embedding method, the method is applied to active devices. The results before and after de-embedding are compared under multiple bias conditions. Furthermore, the results after de-embedding based on the conventional open-short method and the proposed method are compared up to 220 GHz. These results show that using the proposed method can achieve accurate ultrawideband de-embedding up to the terahertz frequency band.
17 citations
TL;DR: In this paper, a novel electromagnetic bandgap power plane etched with multiring complementary split ring resonators (CSRRs) is proposed for effectively suppressing simultaneous switching noise. And the measured insertion losses, i.e., S21-parameters of the two fabricated samples agree well with the simulated ones obtained by using the commercial software HFSS.
Abstract: A novel electromagnetic bandgap (EBG) power plane etched with multiring complementary split ring resonators (CSRRs) is proposed for effectively suppressing simultaneous switching noise. Its equivalent circuit model is derived for predicting its bandwidth numerically. The measured insertion losses, i.e., S21-parameters of the two fabricated samples agree well with the simulated ones obtained by using the commercial software HFSS, respectively. It is shown that –40 dB suppression is achieved over an ultrawideband from 600 MHz to 13.26 GHz, when the two-ring CSRRs EBG power plane is used. While for four-ring CSRRs EBG case, the suppression level can be extended to –60 dB. Comparative studies are also performed on the signal integrity of a pair of differential transmission lines over L-bridge EBG with and without CSRRs, respectively, and similar performance is achieved.
17 citations
TL;DR: In this paper, a lossy filter with flat passband and asymmetric response is proposed by using complex couplings with positive and negative imaginary parts with transmission lines loaded with series and shunt resistors, respectively.
Abstract: A lossy filter with flat passband and asymmetric response is proposed by using complex couplings. The complex coupling coefficients with positive and negative imaginary parts are realized with transmission lines loaded with series and shunt resistors, respectively. Design formulas are derived for the critical parameters. A filter prototype is developed at 4.97 GHz and substrate integrated waveguide resonators with unloaded $Q$ -factor of 450 are used. One transmission zero is located in its upper stopband. The 0.2-dB bandwidth of 279 MHz is achieved and the equivalent $Q$ -factor is about 1900. Good agreement is obtained among the synthesized, simulated, and measured results.
14 citations
TL;DR: In this paper, a comprehensive investigation of the impedance characteristics of power distribution networks (PDNs) made of carbon nanotube through-silicon vias (CNT-TSVs) is presented and validated through three-dimensional full-wave electromagnetic simulator up to 100 GHz.
Abstract: This paper presents a comprehensive investigation of the impedance characteristics of power distribution networks (PDNs) made of carbon nanotube through-silicon vias (CNT-TSVs). The equivalent circuit model of the CNT-TSV array is presented and validated through three-dimensional full-wave electromagnetic simulator up to 100 GHz. By virtue of the circuit model, the inductive properties of CNT-TSVs are characterized and compared for various physical parameters. Then, the PDN impedance characteristics of multiple stacked chip-PDNs with CNT-TSVs are captured and evaluated. It is found that the large CNT kinetic inductance may limit the PDN frequency range. Therefore, the fabrication of CNT-TSVs should be improved to increase the CNT density and reduce the contact resistance.
11 citations
TL;DR: In this paper, a reconfigurable reflectarray antenna with independent control of dual polarizations is proposed by properly assigning the variable capacitances of four varactors, which are placed between metal square rings of each unit.
Abstract: Electromagnetic (EM) waves with orbital angular momentum (OAM) provide a new degree of freedom for channel multiplexing to improve the capacity of wireless communication. For OAM-based systems, it is important to design specific configurations to generate vortex radios. In this paper, a reconfigurable reflectarray antenna is proposed with independent control of dual polarizations. A reflective cell is proposed by properly assigning the variable capacitances of four varactors, which are placed between metal square rings of each unit. The varactors of each unit are divided into two groups and the capacitance value of each group controls the reflection phase for a single linear polarization. By using the equivalent circuit model, the reflective units and array can be designed efficiently. Smooth phase variation and good reflection efficiency are achieved. Then, the reflectarray is set into sectors and a simple phase-shifting surface model is used to generate vortex beam. Each sector is realized with reflective units satisfying desired reflection phases for different modes. This kind of OAM-generating method can reduce the required variation range of reflection phase and provide more choices for a specific OAM mode combination with dual polarization, which is helpful to reduce mutual coupling between the two linear polarizations. Finally, full-wave simulations show that the 0, ±1, ±2 modes of vortex beam are successfully generated at 3.5 GHz with arbitrary combination in dual-polarization, which is also supported by OAM modes purity and reflection efficiency analysis. Therefore, in our design, the reconfigurable OAM and spin angular momentum (SAM), related with polarization, can be utilized simultaneously and independently for high-capacity wireless communication.
11 citations
TL;DR: In this paper, an improved substrate coupling network is developed to characterize the nonlinear phase of S12 when a transistor is under zero-bias condition. And a corresponding parameter extraction technique is proposed to validate this model, a set of transistors fabricated in a commercial 90-nm CMOS process is investigated under multibias conditions.
Abstract: An RF CMOS model incorporating an improved substrate coupling network is developed The proposed model focuses on characterizing the nonlinear phase of S12 when a transistor is under zero-bias condition In addition, a corresponding parameter extraction technique of the model is proposed To validate this model, a set of transistors fabricated in a commercial 90-nm CMOS process is investigated under multibias conditions Comparison between measurement and calculation results shows that good agreement has been achieved, which indicates that the proposed model can accurately characterize the performance of transistors up to 66 GHz
TL;DR: In this paper, the authors compared the power to failure of SiGe-based low-noise amplifiers by injecting high-power microwave pulses and derived a general equation to calculate power-to failure, which depends on pulse width and duty cycle.
Abstract: This study demonstrates comparisons of power to failure for SiGe-based low-noise amplifiers by injecting high-power microwave pulses. A general equation was derived to calculate power to failure, which depends on pulse width and its duty cycle. Two types of silicon–germanium (SiGe) transistors were modeled, and their temperature distributions were simulated. The pulse thermal resistance, thermal capacitance, and breakdown temperature were calculated and determined. Results show that the power to failure of the two transistors depend on the number of slots, pulse thermal resistance, thermal capacitance, and breakdown temperature, although these transistors exhibit nearly similar structures. In addition, calculated and measured results show close correlations. A summary for calculating the power to failure of a type of SiGe transistor is provided.
TL;DR: A compact passive equalizer for differential transmission channel is designed in TSV-based three-dimensional integrated circuits (3-D ICs) and validated by both frequency- and time-domain simulations for 20 Gb/s high-speed differential signaling.
Abstract: In this paper, a compact passive equalizer for differential transmission channel is designed in TSV-based three-dimensional integrated circuits (3-D ICs). The compact size of the equalizer is achieved by a square shunt metal line. Three simplified odd-mode half circuit models are proposed for ground-signal-signal-ground (G-S-S-G) type TSVs, differential on-interposer interconnects, and differential channels, respectively. Those simplified models merely consist of frequency-independent elements and can accurately predict the differential insertion losses up to 20 GHz. Moreover, the electrical parameters of the proposed serial resistance-inductance ( RL ) type equalizers are derived from the system transfer functions and optimized by virtue of the time-domain inter-symbol interference cancellation technique. Further, the geometrical parameters of the RL equalizers are calculated by using a genetic algorithm based multi-objective optimization method. Finally, the performance of the designed RL equalizer is validated by both frequency- and time-domain simulations for 20 Gb/s high-speed differential signaling.
TL;DR: In this paper, a modified finite-difference time-domain (FDTD) method was proposed to characterize the specific absorption rate (SAR) distribution of a human body model in a vehicle-based shelter in the presence of high-power intentional electromagnetic pulse (IEMP) radiation using a modified FDTD method.
Abstract: This paper is devoted to characterizing the specific absorption rate (SAR) distribution of a human body model in a vehicle-based shelter in the presence of high-power intentional electromagnetic pulse (IEMP) radiation using a modified finite-difference time-domain (FDTD) method. The proposed method combines the FDTD(2, 4) method along with dielectric conformal techniques, where the updating equations of FDTD(2, 4) method are modified by introducing an effective dielectric constant and a new conductivity derived by area average of different dielectric regions including coating layer in nine spatial discrete cells. Numerical results show that our method even with coarse meshes has good agreements and efficiency comparing with the traditional FDTD method and CST simulation tool. Furthermore, the proposed method is applied to predict the SAR distribution of human body in a vehicle-based metallic shelter, where the peak SAR and average SAR are captured and compared in the presence of an IEMP with different polarizations and incident angles.
TL;DR: In this article, a special measurement system is set up to get reliability of the bonding wire array, where a microscope is used to capture its fractures. And an improved LDMOS design in optimizing the bonding wires profile is proposed.
Abstract: Electro-thermo-stress (ETS) failure of bonding wire array in a laterally diffused metal oxide semiconductor (LDMOS) field-effect transistor (FET)-based power amplifier during its high power’s ruggedness experiment is investigated in this paper. A special measurement system is at first set up to get reliability of the bonding wire array, where a microscope is used to capture its fractures. The temperature distribution of the LDMOSFET die surface and bonding wire array is also captured by a thermal infrared scanner to investigate the principle underlying the failure of ETS fractures. Simulation studies are also performed. The temperature distribution is closely related to the profiles of the bonding wire array. Numerical methods are employed to calculate the bonding wire array, and the temperature distributions are demonstrated by using our finite-element method code. It also works well in solving the transient temperature of the bond wire array with the stationary current and the heat source from the silicon region. The simulated thermal results agree well with the testing results. Finally, an improved LDMOS design in optimizing the bonding wire profile is proposed. This research can serve as a guide for the design of an LDMOS PA with enhanced reliability.
TL;DR: In this article, a self-developed electrothermal co-simulation solver was used to solve the full-wave electromagnetic equation and the steady heat conduction equation using the finite-element method.
Abstract: In this paper, high-frequency electrothermal characteristics of the power delivery network (PDN) are investigated for through-silicon-via (TSV)-based 3-D ICs by utilizing a self-developed electrothermal co-simulation solver The solver circularly solves the full-wave electromagnetic equation and the steady heat conduction equation using the finite-element method The preconditioned biconjugate gradient method combined with the element-by-element approximate factorization method is employed to speed up the simulation and save memory cost Based on the solver, the impacts of the excitation condition and dielectric loss tangent are analyzed for a one-chip power grid, while the influence of TSV location is studied for a two-chip PDN structure In the modeling, both the conductor and dielectric losses are taken into account, and the temperature dependence of material parameters is treated appropriately As results, PDN impedance and self-heating-induced temperature rise are emphatically analyzed in a wide frequency range, and the electric field and temperature distributions of several resonance modes are presented The results would be beneficial for the design and thermal management of 3-D PDNs
01 Jan 2018
TL;DR: A new design method is proposed for filters with equal-ripple negative group delay (NGD) by combining the coupling matrix of bandstop filter with the nonuniform-ß technique, and the equal- Ripple NGD characteristic is achieved.
Abstract: A new design method is proposed for filters with equal-ripple negative group delay (NGD). By combining the coupling matrix of bandstop filter with the nonuniform-s technique, the equal-ripple NGD characteristic is achieved. The ripple is mainly determined by the minimum dissipation factor of resonators, while the NGD is controlled by the maximum insertion loss and dissipation factors. A prototype is developed at 2.0 GHz, with the measured NGD of −3.1 ns and NGD ripple of −0.5 ns within the bandwidth of 85 MHz.
01 Aug 2018
TL;DR: In this article, the average per unit-length parameters of a twisted-wire pair (TWP) near a reference wire are derived for two typical cases, i.e., the reference conductor is inside or outside the TWP, respectively.
Abstract: Efficient characterization of field-to-wire coupling in twisted-wire pair (TWP) near a reference wire is performed in this paper. The averaged-per-unit-length parameters of this transmission line system are first derived for two typical cases, i.e. the reference conductor is inside or outside the TWP, respectively. The induced voltage sources for describing the field-to-wire coupling are determined analytically in closed form. The proposed model is able to fast predict both common mode and differential mode currents induced at the terminals of such system, and it is validated in comparison with the full-wave solution obtained by commercial software FEKO, with the simulation time reduced greatly.
TL;DR: In this article, a discontinuous Galerkin time-domain integral equation method based on a marching-on-in-degree (MOD) scheme for simulating transient responses of perfect electric conductor objects is proposed.
Abstract: A discontinuous Galerkin time-domain electric field integral equation method based on a marching-on-in-degree (MOD) scheme for simulating transient responses of perfect electric conductor objects is proposed in this letter. With the help of half-Rao–Wilton–Glisson spatial basis functions, we can simulate transient scattering responses of three-dimensional structures with either conformal or nonconformal meshes. The weighted Laguerre polynomials are chosen as temporal basis functions and implemented for the MOD scheme. Under such circumstances, the developed algorithm eliminates late-time instabilities and the limitation of Courant–Friedrichs–Lewy criteria. In addition, we adopt a fast-Fourier-transform-based blocking scheme to accelerate the temporal convolution of the MOD procedure. Some numerical examples are given to validate its stability and accuracy.
08 Jul 2018
TL;DR: In this article, a microstrip grid array antenna is presented for dual band applications at 2.27 GHz and 17.7 GHz, where the antenna can operate at two modes.
Abstract: A microstrip grid array antenna is presented for dual band applications at 2.27 GHz and 17.7 GHz. By designing the location of the feed point, the antenna can operate at the two modes. One mode is corresponding to the normal operating scheme of the grid array antenna in the high frequency band. The other mode is similar with the operating scheme of the patch antenna in the low frequency band. The simulated results of the antenna are given and discussed.
01 Aug 2018
TL;DR: In this article, the optimal strain orientation and magnitude are identified for a ultra-thin-body (UTB) silicon double-gate (DG) P-MOSFET at 7nm gate length and 3nm channel thickness.
Abstract: Strain has been proved to be an effective approach to boost CMOS device performances. As channel length being scaled to sub-10nm, strain needs to be carefully optimized with quantum effects fully accounted for. In this work, optimal strain orientation and magnitude are identified for a ultra-thin-body (UTB) silicon double-gate (DG) P-MOSFET at 7nm gate length and 3nm channel thickness. The optimization is based on accurate quantum transport simulations using the nonequilibrium Green’s function (NEGF) approach and strained sixband k·p model. Various confinement and transport crystal orientations, different types of strain, and a range of strain strengths are considered. Device performances such as the ballistic ON-state current (ION) and subthreshold swing (SS) are extracted and compared. Analysis shows strong correlation between strain and source-to-drain tunneling (SDT) effect.
TL;DR: In this article, the authors performed computational study of nanopillar Si/poly (3,4-ethylene dioxythiophene):poly (styrenesulfonate) (PEDOT:PSS) heterojunction solar cell by using finite element method to solve Poisson equation, drift-diffusion equations, and current continuity equations.
Abstract: Computational study of nanopillar Si/poly (3,4-ethylene dioxythiophene):poly (styrenesulfonate) (PEDOT:PSS) heterojunction solar cell is performed by using finite element method to solve Poisson equation, drift-diffusion equations, and current continuity equations. The depletion width around the edge of the Si nanopillar is almost the same as that of planar junction, while the depletion width around the middle of the Si nanopillar is much wider than that of planar junction. As a result, besides the enhanced light absorption due to light trapping induced by nanopillar array as in previous studies, larger depletion region, which leads to higher electron-hole separation efficiency under light illumination, is another reason for short-circuit current increase of nanopillar solar cell. The reason for less open-circuit voltage of nanopillar solar cell is also clarified by explaining the reason for large dark current of the nanopillar solar cell compared to its planar structure counterpart as follows. The kink of the potential profile along the lines around the edge nanopillar leads to much sharper potential drop in the following depletion region, and results in greater hole density slope when the solar cells are forwarded biased. Since the Si/PEDOT:PSS behaves like a pn junction rather than a Schottky junction as clarified in the previous study and the PEDOT:PSS is much highly doped, nanopillar heterojunction has larger dark current than planar junction due to the larger hole diffusion current around Si nanopillar edge.
01 Jul 2018
TL;DR: In this paper, the authors compared the power to failure of SiGe-based low-noise amplifiers by injecting high-power microwave (HPM) pulses, and found that the number of slots, thermal resistance, thermal capacitance, and breakdown temperature of the SiGe transistors depend on the number and number of transistors.
Abstract: This study demonstrates comparisons of power to failure for SiGe-based low-noise amplifiers by injecting high-power microwave (HPM) pulses. Two types of silicon-germanium (SiGe) transistors were modeled, and their temperature distributions were simulated. The pulse thermal resistance, thermal capacitance, and breakdown temperature were calculated and determined. Results show that the power to failure of the two transistors depend on the number of slots, pulse thermal resistance, thermal capacitance, and breakdown temperature, although these transistors exhibit nearly similar structures. In addition, calculated and measured results show close correlations.
TL;DR: The numerical results show that with this effective coarse-level correction, the residual errors introduced by adaptive refined systems can be eliminated quickly by the DDM and optimal performance in terms of simulation time is achieved, regardless of workload imbalances during the adaptive steps.
Abstract: Adaptive process of finite-element method always needs to solve a set of linear systems repeatedly. This communication proposes an accurate and efficient domain decomposition method (DDM) based on a multilevel algorithm and a coarse-level correction strategy. Our developed algorithm facilitates the adaptive refinement process utilizing dynamic coarse-level correction, exploits the hierarchical feature of the refined systems through p-type multigrid method in subdomains, then solves the lowest order system through algebraic multigrid method in auxiliary and node-based spaces. The numerical results show that with this effective coarse-level correction, the residual errors introduced by adaptive refined systems can be eliminated quickly by the DDM. Besides, optimal performance in terms of simulation time is achieved, regardless of workload imbalances during the adaptive steps. Several large-scale electromagnetic problems are analyzed for accuracy as well as performance evaluation of the proposed method.
TL;DR: In this article, a selection of research topics related to nano-electromagnetic compatibility (nano-EMC) issues in emerging carbon nanoelectronics are presented. And the key techniques of carbon nanotube-filled through-silicon vias and carbon-based passive devices are discussed.
Abstract: This paper presents a selection of research topics related to nano-electromagnetic compatibility (nano-EMC) issues in emerging carbon nanoelectronics Carbon-based nano-interconnect modeling and analysis are first introduced Then, the key techniques of carbon nanotube-filled through-silicon vias and carbon- based passive devices are discussed
TL;DR: In this article, the authors performed a computational study of atomically thin monolayer MoS2/WSe2 heterojunction with focus on carrier dynamics and thermal transport by using finite-difference method to solve carrier transport equations and heat conduction equation.
Abstract: Computational study of atomically thin monolayer MoS2/WSe2 heterojunction with focus on carrier dynamics and thermal transport is performed by using finite-difference method to solve carrier transport equations and heat conduction equation. Carrier transport in the horizontal direction is in the micrometer scale, while in the vertical direction it is on the subnanometer scale. Carrier transport is modeled as diffusive transport in the horizontal direction with tunneling-assisted carrier recombination between two monolayers in the vertical direction as in the previous study. Band profile, quasi-Fermi level splitting, carrier distribution, and heat generation are investigated in detail. The heterojunction with high-doping concentration has larger current compared to that with low-doping concentration. Heat generation has two components which are due to the Joule heating and inelastic carrier recombination, respectively. The former is provided by the applied voltage, while the latter is from surrounding environment which acts as thermal reservoir. Since the heterojunction works very differently from the conventional p-n diode, it is compared to typical field-effect transistors due to similar device structures. The heat generation of the heterojunction is eight orders lower than that of typical nanoscale field-effect transistors because of its low-current density. Temperature increase in the heterojunction is also several orders of magnitude lower compared to typical nanoscale field-effect transistors.
Posted Content•
TL;DR: In this article, the authors proposed a class of kirigami-based metamaterials whose electromagnetic functionalities can be switched between nonchiral and chiral states by stretching the predesigned split-ring resonator array.
Abstract: The ancient paper craft of kirigami has recently emerged as a potential tool for the design of functional materials. Inspired by the kirigami concept, we propose a class of kirigami-based metamaterials whose electromagnetic functionalities can be switched between nonchiral and chiral states by stretching the predesigned split-ring resonator array. Single-band, dual-band and broadband circular polarizers with reconfigurable performance are experimentally demonstrated with maximum circular dichroisms of 0.88, 0.94 and 0.92, respectively. The underlying mechanism is explained and calculated via detailed analysis of the excited multipoles, including the electric, magnetic, and toroidal dipoles and quadrupole. Our approach enables tailoring the electromagnetic functionalities in kirigami patterns and provides an alternate avenue for reconfigurable optical metadevices with exceptional mechanical properties.
08 Jul 2018
TL;DR: In this paper, the discontinuous Galerkin time-domain electric field integral equation method based on marching-on-in-degree scheme (DG-TDEFIE-MOD) is proposed for simulating transient electromagnetic responses of some multiscale and non-conformal PEC structures.
Abstract: The discontinuous Galerkin time-domain electric field integral equation method based on marching-on-in-degree scheme (DG-TDEFIE-MOD) is proposed for simulating transient electromagnetic responses of some multiscale and non-conformal PEC structures. With the implementation of both DG method and MOD scheme, the developed algorithm is used to simulate transient scattering and radiation responses of either conformal or non-conformal meshed geometries, where late-time instability is successfully eliminated. Some numerical examples are given to validate its stability and accuracy.