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- 2018
- computer statistical experiment
- statistical optimization
- resonant-tunneling diode
- negative voltage current differential resistance
- characteristics
- heterojunction
- quantum well
- resonant tunneling border
- Electronic Science and Technology
- Optoelectronic Information Science and Engineering
- Bauman Moscow State Technical University
- V.N. Karazin Kharkiv National University
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Charge transport in graphene-based mesoscopic realizations of Sachdev-Ye-Kitaev models
摘要： We consider a recent proposal for a physical realization of the Sachdev-Ye-Kitaev (SYK) model in the zeroth-Landau-level sector of an irregularly shaped graphene flake. We study in detail charge transport signatures of the unique non-Fermi-liquid state of such a quantum dot coupled to noninteracting leads. The properties of this setup depend essentially on the ratio p between the number of transverse modes in the lead M and the number of the fermion degrees of freedom N on the SYK dot. This ratio can be tuned via the magnetic field applied to the dot. Our proposed setup gives access to the nontrivial conformal-invariant regime associated with the SYK model as well as a more conventional Fermi-liquid regime via tuning the field. The dimensionless linear-response conductance acquires distinct p dependencies for the two phases, respectively, in the low-temperature limit, with a universal jump at the transition. We find that corrections scale linearly and quadratically in either temperature or frequency on the two sides of the transition. In the weak-tunneling regime, we find differential conductance proportional to the inverse square root of the applied voltage bias U for bias energy eU larger than temperature scale kB T. This dependence is replaced by a conventional Ohmic behavior with constant conductance proportional to 1/sqrt(T) for bias energy eU smaller than temperature scale kB T. We also describe the out-of-equilibrium current-bias characteristics and discuss various crossovers between the limiting behaviors mentioned above.
关键词： Sachdev-Ye-Kitaev model,tunneling conductance,graphene,quantum dot,charge transport,non-Fermi-liquid,conformal invariance
更新于2025-09-23 15:23:52
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Investigation of Disorder in Mixed Phase, <i>sp</i> <sup>2</sup> – <i>sp</i> <sup>3</sup> Bonded Graphene-Like Nanocarbon
摘要： Disorder in a mixed phase, sp2–sp3 bonded graphene-like nanocarbon (GNC) lattice has been extensively studied for its electronic and field emission properties. Morphological investigations are performed using scanning electron microscopy (SEM) which depicts microstructures comprising of atomically flat terraces (c-planes) with an abundance of edges (ab planes which are orthogonal to c-planes). Scanning tunneling microscopy (STM) is used to observe the atomic structure of basal planes whereas field emission microscopy (FEM) is found to be suitable for resolving nano-topography of edges. STM images revealed the hexagonal and non-hexagonal atomic arrangements in addition to a variety of defect structures. Scanning tunneling spectroscopy is carried out to study the effect of this short-range disorder on the local density of states. Current versus voltage (I–V) characteristics have been recorded at different defect sites and are compared with respect to the extent of the defect. As sharp edges of GNC are expected to be excellent field emitters, because of low work function and high electric field, enhancement in current is observed particularly when applied electric field is along basal planes. Therefore, it is worthwhile to investigate field emission from these samples. The FEM images show a cluster of bright spots at low voltages which later transformed into an array resembling ledges of ab-planes with increasing voltage. Reproducible I–V curves yield linear Fowler-Nordheim plots supporting field emission as the dominant mechanism of electron emission. Turn on field for 10 μA current is estimated to be ～3 V/μm.
关键词： Field Emission Microscopy,Graphene-Like Nanocarbon,Scanning Tunneling Spectroscopy,Scanning Tunneling Microscopy
更新于2025-09-23 15:22:29
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[IEEE 2018 International Conference on Simulation of Semiconductor Processes and Devices (SISPAD) - Austin, TX, USA (2018.9.24-2018.9.26)] 2018 International Conference on Simulation of Semiconductor Processes and Devices (SISPAD) - Electron-only explicit screening quantum transport model for semiconductor nanodevices
摘要： State of the art quantum transport models for semiconductor nanodevices attribute negative (positive) unit charges to states of the conduction (valence) band. Hybrid states that enable band-to-band tunneling are subject to interpolation that yield model dependent charge contributions. In any nanodevice structure, these models rely on device and physics specific input for the dielectric constants. This work exemplifies the large variability of different charge interpretation models when applied to ultrathin body transistor performance predictions. To solve this modeling challenge, an electron-only band structure model is extended to atomistic quantum transport. Performance predictions of MOSFETs and tunneling FETs confirm the generality of the new model and its independence of additional screening models.
关键词： tunneling FET,Electron-only,ultrathin body transistor,NEGF
更新于2025-09-23 15:22:29
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[IEEE 2018 International Conference on Simulation of Semiconductor Processes and Devices (SISPAD) - Austin, TX, USA (2018.9.24-2018.9.26)] 2018 International Conference on Simulation of Semiconductor Processes and Devices (SISPAD) - A Simulation Perspective: The Potential and Limitation of Ge GAA CMOS Devices
摘要： The electrical characteristics of <110> n/p Ge nanowire transistors (NWTs) with the cross section of 6×6nm2 have been studied. The ION performance and the subthreshold swing are simulated by multi-subband Boltzmann transport equation and ballistic quantum transport solvers, respectively. The performance of <110> nGe NWTs is sensitive to the barrier height of interfacial layer due to highly-anisotropic Λ-valleys. The dimension-dependent k·p parameters based on tight-binding full band are used to address the strong confinement of pGe NWTs. Comparing to Si NWTs, the intrinsic ION is twice as high for both n/p Ge NWTs at 28nm channel length. As the channel length is scaled down, such ION benefit is maintained till the tunneling effect comes in and degrades the subthreshold swing.
关键词： source-to-drain tunneling,Ge,ballistic ratio,nanowire,CMOSFETs,interfacial layer
更新于2025-09-23 15:22:29
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Microstrip Line Impedance Matching Using ENZ Metamaterials, Design and Application
摘要： The idea of this paper is to extend the tunneling effect of epsilon-near-zero (ENZ) narrow channel for matching two microstrip lines with different impedance characteristics. The main advantage of this method is the possibility to design a channel with subwavelength electrical size and obtain similar matching condition when compared with a conventional λ/4-transformer. The bandwidth of the structure is directly related to the bandwidth of the ENZ-metamaterials (MTM). The suggested matching circuit is comprised of a metallic wall and an ENZ narrow channel. To realize the ENZ channel, a rectangular waveguide which operates in TE10 mode is designed and implemented using a substrate integrated waveguide (SIW) technology. A set of vias are also needed for emulating the metallic wall to reduce the ENZ channel cross section. The proposed structure for different impedance values of 50?, 100?, and 150? was designed, simulated, fabricated, and tested. Moreover, as an important application of a matching network, a microstrip patch antenna has been matched over the desired frequency band. Simulation results based on CST microwave studio have good agreement with measurements. It is shown that the bandwidth of the circuit is 8%–15%.
关键词： impedance matching,metamaterials (MTM),Epsilon-near-zero (ENZ),microstrip line,tunneling
更新于2025-09-23 15:22:29
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Reverse bias-dependence of schottky barrier height on silicon carbide: influence of the temperature and donor concentration
摘要： The work deals with the dependences of the Schottky barrier height (SBH) on the reverse bias voltage, temperature and on donor concentration of metal/4H-SiC Schottky diodes. Using the tunneling modeling we have shown that the Schottky barrier height on silicon carbide strongly depends on the reverse bias voltage, temperature and doping concentration. At room temperature, the Schottky barrier height increases with increasing the reverse bias voltage at high doping concentration (about 1016 cm-3), while, at low doping concentration (about 1015 cm-3) the Schottky barrier height decreases with increasing the reverse bias voltage. These behaviors are independent of the Schottky barrier lowering effect. That means other effects occur at the barrier and depend on the reverse applied bias. The barrier height increases with increasing temperature and doping concentration under reverse bias conditions. The barrier heights extracted from the Padovani-Stratton formulas are close to the barrier heights extracted from the Tsu-Esaki formula in particular for the thermionic-field emission.
关键词： Reverse Bias,Silicon Carbide,Extraction,Tunneling,Schottky Barrier Height
更新于2025-09-23 15:22:29
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Long-Range Activationless Photostimulated Charge Transport in Symmetric Molecular Junctions
摘要： Molecular electronic junctions consisting of nitroazobenzene oligomers covalently bonded to a conducting carbon surface using an established 'all-carbon' device design were illuminated with UV?vis light through a partially transparent top electrode. Monitoring junction conductance with a DC bias imposed permitted observation of photocurrents while varying the incident wavelength, intensity, molecular layer thickness, and temperature. The photocurrent spectrum tracked the in situ absorption spectrum of nitroazobenzene, increased linearly with light intensity, and depended exponentially on applied bias. The electronic characteristics of the photocurrent differed dramatically from those of the same device in the dark, with orders of magnitude higher conductance and very weak attenuation with molecular layer thickness (β = 0.14 nm?1 for thickness above 5 nm). The temperature dependence of the photocurrent was opposite that of the dark current, with a 35% decrease in conductance between 80 and 450 K, while the dark current increased by a factor of 4.5 over the same range. The photocurrent was similar to the dark current for thin molecular layers but greatly exceeded the dark current for low bias and thick molecular layers. We conclude that the light and dark mechanisms are additive, with photoexcited carriers transported without thermal activation for a thickness range of 5?10 nm. The inverse temperature dependence is likely due to scattering or recombination events, both of which increase with temperature and in turn decrease the photocurrent. Photostimulated resonant transport potentially widens the breadth of conceivable molecular electronic devices and may have immediate value for wavelength-specific photodetection.
关键词： charge transport,optoelectronics,photocurrent,molecular electronics,molecular orbital energy,tunneling barrier,HOMO?LUMO gap,photoinduced transport
更新于2025-09-23 15:22:29
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Phonon-assisted tunneling in direct-bandgap semiconductors
摘要： In tunnel ?eld-effect transistors, trap-assisted tunneling (TAT) is one of the probable causes for degraded subthreshold swing. The accurate quantum-mechanical (QM) assessment of TAT currents also requires a QM treatment of phonon-assisted tunneling (PAT) currents. Therefore, we present a multi-band PAT current formalism within the framework of the quantum transmitting boundary method. An envelope function approximation is used to construct the electron-phonon coupling terms corresponding to local Fr?hlich-based phonon-assisted inter-band tunneling in direct-bandgap III-V semiconductors. The PAT current density is studied in up to 100 nm long and 20 nm wide p-n diodes with the 2- and 15-band material description of our formalism. We observe an inef?cient electron-phonon coupling across the tunneling junction. We further demonstrate the dependence of PAT currents on the device length, for our non-self-consistent formalism which neglects changes in the electron distribution function caused by the electron-phonon coupling. Finally, we discuss the differences in doping dependence between direct band-to-band tunneling and PAT current.
关键词： phonon-assisted tunneling,quantum-mechanical modeling,tunnel ?eld-effect transistors,electron-phonon coupling,direct-bandgap semiconductors
更新于2025-09-23 15:22:29
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Tunable Spin Seebeck Diode with Magnonic Spin Tunneling Junction
摘要： We theoretically investigate the spin–wave spin current induced by the spin Seebeck effect in magnonic spin tunneling junctions (MSTJs) for arbitrary magnetization directions. We show that the MSTJ functions as a tunable spin Seebeck diode in which the tunneling spin current can be turned on and off with high efficiency by controlling the magnetization direction.
关键词： spin current,spin Seebeck effect,diode,magnetization direction,magnonic spin tunneling junction
更新于2025-09-23 15:22:29
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Electron transfer during binding processes between thiolate molecules and Au nano-islands
摘要： We investigated electron transfer during the time-dependent binding processes between thiolate molecules and Au nano-islands by observing tunneling current with an interdigitated microelectrode supporting the sputtered Au nano-islands (IME@AuNI). The time-dependent optical and electrical signal variation during the binding process was examined for five kinds of thiolates. As the immersion time was prolonged, the optical absorbance increased, whereas the current passing through the IME@AuNI decreased. Importantly, the spectral and current characteristics depended on the thiolate structure, because of the formation of capping layer in accordance with thiolate structure. These results are mainly attributed to synergistic effects of electron transfer from Au nano-islands to thiolate molecules and bridging effects of thiolate molecules among Au nano-islands.
关键词： Au nano-islands,Thiolate molecules,Electron transfer,Localized surface plasmon resonance,Tunneling current
更新于2025-09-23 15:22:29