1,721,029 research outputs found
Nanoscale ferroelectrics for advanced electronics and microwave applications [Guest Editorial]
No full textA full-wave time-dependent Schrödinger equation approach for the modeling of asymmetric transport in geometric diodes
No full textDesign and modeling of geometric diodes can be really challenging as it requires a rigorous quantum analysis at the nanoscale, accurate enough to capture the asymmetric behavior of charge transport. In this paper, we present a full-wave Time-Dependent Schrödinger Equation (TDSE) approach to model coherent transport in a two-dimensional geometric diode defined by an asymmetric taper of the domain where the charges are confined. The proposed solution clearly shows asymmetric transport, and provides a description of the rectification behavior in response to a parametric change. In general, the above model can account for even more complex geometries in order to optimize diodes performance
Current-Voltage Characterization of Multi-Port Graphene Based Geometric Diodes for High-Frequency Electromagnetic Harvesting
Full text linkIn this contribution, geometric diodes based on graphene patterned with spatial asymmetry have been studied, starting from tight-binding numerical approximation in a self-consistent framework, to verify their potential for electromagnetic (e. m.) harvesting. We report a detailed analysis of coherent charge transport and provide some figures of merit with respect to e. m. rectification, such as, for instance, the asymmetry of the dark current-voltage characteristics. The most important achievement of this work is given by the accurate analysis of the main key physical/geometric parameters that affect the nonlinear response of the diodes, for different configurations and geometries. Owing to the Scattering Matrix approach, introduced elsewhere for coherent transport calculation, it was possible to cascade asymmetric discontinuities and simulate large structures (more than 100K atoms) in a modular fashion. In this way, simulation at the atomistic level can be brought up to the device level to provide guidelines for design and fabrication, in view of practical applications related to clean-energy harvesting/rectification up to infrared and solar-light frequencies
Self-Consistent and Full-Wave Analysis of Carbon-Nanotube Matrices for Multi-Channel Charge Confinement
No full textThis paper reports a theoretical characterization of carbon nanotubes matrices using a full-wave undulatory description of charge carriers, self-consistent with external and self-generated potentials. The effect of nanotubes coupling on charge and current confinement is described, by a new in-house simulation toolkit that can easily solve for 3D arrays of packed nanotubes, possibly multi-wall, in a multi-band framework. The availability of such a tool could be of crucial importance in view of the multiplicity of nanotechnology applications of CNT arrays as sensors, field effect transitors, quantum dots, interconnects and antennas
Nano-scale electronics: Rigorous quantum study of a single molecule device
No full textA single molecule made of carbon atoms, namely C100, has been rigorously simulated for application in quantum electronics and related devices. A self-consistent calculation, using density functional theory and a master-slave perturbation approach, has been done in order to characterize the curren-voltage curves of the above nano-scale component, that could be the building block for future device concepts based on quantum transport. Charging effects, quantum tunneling, ballistic transport, are shown to characterize the device under study, making it an important element of a potential scalable platform for unconventional electronics with extremely high charge sensitivit
Efficient and versatile modeling of mono-and multi-layer MoS2 field effect transistor
No full textTwo-dimensional (2D) materials with intrinsic atomic-level thicknesses are strong candidates for the development of deeply scaled field-effect transistors (FETs) and novel device architectures. In particular, transition-metal dichalcogenides (TMDCs), of which molybdenum disulfide (MoS2) is the most widely studied, are especially attractive because of their non-zero bandgap, mechanical flexibility, and optical transparency. In this contribution, we present an efficient full-wave model of MoS2-FETs that is based on (1) defining the constitutive relations of the MoS2 active channel, and (2) simulating the 3D geometry. The former is achieved by using atomistic simulations of the material crystal structure, the latter is obtained by using the solver COMSOL Multiphysics. We show examples of FET simulations and compare, when possible, the theoretical results to the experimental from the literature. The comparison highlights a very good agreement
Cosec2 hybrid travelling/resonant antenna for maritime surveillance applications
No full textIn this contribution, the authors present guidelines for an effective design of an X-band 2D array of slotted waveguides for surveillance applications. The radiation pattern, with a narrow beam and cosec2 profile, respectively, in azimuth and in elevation, is obtained by a beam forming network based on a hybrid architecture, in which the main corporate feed line feeds identical 11-element travelling wave slotted arrays. The latter produces a radiation pattern that is frequency-independent in azimuth and only slightly frequency-dependent in elevation. The fabricated antenna features a horizontal beam width (at -3 dB) of 1.16°, gain >31 dBi, and 30 dB sidelobe level in the 300 MHz operative band. The overall array is made up of three stacked layers: the first two for the corporate feed line and the third for the travelling wave radiating elements, resulting in remarkably compact external dimensions (170 cm × 25 cm × 2 cm) and relatively low weight (8 kg in total)
Metamaterial-Based Planar GRIN Lens Antenna for D-Band Wireless Communications
No full textThis paper presents a metamaterial-based planar GRIN lens antenna for wireless communications, modeled and designed using COMSOL Multiphysics. The antenna is designed to work at 140 GHz in the D-band, proposed for the next mobile generation (6G). Such devices could be produced by using the SiGe technology, that allows large scale production. The proposed device shows a 11 dB gain in the center band. This value is about five times higher than the same antenna without the lens
Ab-initio simulation of single carbon-cluster electron device
No full textA non-symmetrical C100 Fullerene molecule enclosed by three electrodes (source, drain, gate) made of gold has been chosen as the test configuration for single electron device (SET). Quantum transport of single electrons, under direct control of external electrodes has been rigorously simulated by density functional theory (DFT). The importance and the potential of the above device include operation at low power, and uniquely high charge sensitivity due to Coulomb blockade, possibly observable up to the room temperatur
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