1,721,069 research outputs found
Procedimento per la fabbricazione di canali nanometrici
No full textBrevetto Politecnico di Milano TO 2008 A 39
Quantum-constriction rectifier
No full textA simple quantum constriction (wide-narrow geometry) is found to act as a rectifier in the coherent transport regime if Fermi energy is between the propagation thresholds of the wide and narrow parts. Therefore a simple diode could consist of only two identical leads of different widths. The current-voltage characteristics of this structure are calculated for several temperatures and lead widths, and generalized to other cases by appropriate scaling rules. The rectification properties disappear as the temperature or the size of the system increase. This structure also exhibits regions of negative-differential resistanc
Magnetotransport in the quantum interference resonator
No full textWe examine quantum-mechanical transmission in the T-shape quantum interference resonator. The system is interesting as a potential quantum transistor. The modulation of the transmission as electron energy is varied is almost 100% irrespective of disorder. However, in the magnetic field, transmission modulation reduces, and for strong magnetic fields completely disappears
Electronic transport in quantum waveguide systems with attached stubs
No full textSingle-mode quantum transmission properties of a quantum waveguide system with attached stubs are studied in the ballistic regime. The formation of energy bands is achieved in the case of periodic structure mainly around the energies where a single stub possesses antiresonances. A single defect in the otherwise periodic structure introduces a resonant (or an antiresonant) state. We find that this state is not an exponentially localized state, and is not a Fano-type resonance (although it originates from it), but more a well-known Lorentzian-shaped Breit-Wigner transmission resonance. When this state falls in the energy band, then it forms an antiresonance. A strong magnetic field creates additional quasibound states
Mesoscopic diode
No full textHere we discuss the possibility of an alternative rectifying structure which operates in the world of mesoscopic devices. A simple quantum constriction (wide–narrow geometry) is found to act as a rectifier in the coherent transport regime if Fermi energy is between the propagation thresholds of the wide and narrow parts. Also a quantum structure is proposed which is predicted to operate as a rectifier at room temperatures. This diode for the nanostructures is a quantum wire with an asymmetric quantum constriction (AQC) which works in the coherent transport regime. Structurally imperfect mesoscopic diodes retain rectifying features, although the actual I–V characteristics are different in comparison to the perfect devices
The nonlinear transport regime of a T‐shaped quantum interference transistor
No full textWe present the current–voltage characteristics of a T‐shaped semiconductor electron waveguide structure in the nonlinear regime. This system is interesting as a potential quantum interference transistor. Calculated zero‐temperature I–V characteristics are with multiple peaks and exhibit regions of negative‐differential resistance. The peak‐to‐valley ratio has maximum value of 3:1. The calculated values of the transconductance and the differential drain conductance are small, which suggests limited abilities for conventional applications of the transistor
Conductance of quantum interference transistors in parallel and in series
No full textWe theoretically study the electronic conductance G and the current–voltage characteristics of two quantum interference transistors in parallel and in series. We use two different definitions of conductance, G ~ T and G ~ T / R. Neither can reproduce the classical additivity law in the case of coherent transport due to quantum interference for the elements in series and quasibound states when elements are in parallel. In the case of two transistors in series, we find that the quantityT / R only qualitatively better represents the additivity law, which is probably expected because this model avoids counting the contact resistance twice. However, for the parallel configuration of transistors, the conductance is almost additive for the majority of energies when G ~ T, except for the single-mode regime. Possible use of these configurations in digital electronics for basic logic functions is discussed
Integrated complementary graphene inverter
No full textThe operation of a digital logic inverter consisting of one pp- and one nn-type graphene transistor integrated on the same sheet of monolayer graphene is demonstrated. Both transistors initially exhibited pp-type behavior at low gate voltages, since air contamination shifted their Dirac points from zero to a positive gate voltage. Contaminants in one transistor were removed by electrical annealing, which shifted its Dirac point back and therefore restored nn-type behavior. Boolean inversion is obtained by operating the transistors between their Dirac points. The fabricated inverter represents an important step toward the development of digital integrated circuits on graphene
Scaling meander inductors from micro to nano
No full textIn order to efficiently scale down RF circuits it is necessary also to decrease the size of the inductors. The ultimate limit of this miniaturization would be an RF circuit consisting of nano-scaled inductors. Meander nanoinductors presented in this work were fabricated by electron beam lithography. Their performance was investigated by electromagnetic simulation software. It was found that inductance and quality factor of these inductors linearly scale down with their size. Nano-inductors could offer advantages at higher frequencies because their quality factor linearly increases with frequency in the range where the quality factor of the microinductors reaches a maximum
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