![]() ![]() In this paper, with a GQD as the basic building block, we construct a fundamental two-terminal energy filter where NDR is obtained at low bias and quantum tunnelling achieves high peak-to-valley current ratio (PVCR). In the above-mentioned systems, even though NDR behaviours can be generated, they occur at a relatively high bias (1–2 V), which can limit their application to low power electronics. 23 reported upon experiments where a pronounced negative differential resistance was observed in the current-voltage characteristics of a single molecule located in a break junction. 22 focused on the transport properties of GQDs sandwiched between two semi-infinite zigzag-edged GNR electrodes, showing that the size of QDs effects the number and position of resonant peaks Perrin et al. 14 studied the electron transport properties of a C 60-based electronic device, where two C 60s were linked by an alkane chain, and highlighted that the NDR can be controlled by the length of the linker Zhang et al. Several methods have been investigated to obtain a pronounced NDR effect, including adsorption of different molecules on quantum dots, varying the shape of quantum dots, use of specific materials as electrodes, etc. This property can be considered in building electron energy band-pass filters. The discrete energy distribution in QDs allows for interesting current-voltage characteristics to be observed where contrary to the conventional Ohmic relationship holding, a decrease in current is noticed with the increase in applied bias when NDR is presented. Unique electronic properties in quantum dots include: highly nonlinear I-V characteristics, negative differential resistance (NDR) and electrical switching 15, 16, 17. Because of the quantum confinement, quantum dots have sharper density of state distributions than higher dimensional structures, which has led to them being investigated for use in diode lasers, amplifiers, biological sensors, etc. The study of electron transport in QD-based devices has been one of the foci in quantum physics 13. Dimensional confinement on devices leads to discrete energy levels 9, 10, 11 which can serve as energy filters as only electrons whose energies match the discrete energy levels are allowed to participate in the tunnelling 12 and transport, therefore helping to limit the total current noise and power dissipation. The reduction of the noise then leads to the reduction of the signal and consequently the power required to achieve the same signal-to-noise ratio (SNR). If the integral interval is reduced, the value of the integral, because the noise power spectral density at any energy level is a positive number or zero, will also reduce. This is because the total current noise is the integration of the noise density, a positive definite quantity, over all the allowable energy levels. Considering equations (1, 2, 3, 4), it can be seen that the decrease of noise can be achieved by reducing the energies of electrons that participate in the transport. Reducing energy dissipation and noise in nanoscale electronics are important challenges in the design of 2-D circuits and systems. These results may shed light on the design of real connecting components in nanocircuits.Where G is the total conductance, N E is the current noise over a finite energy domain, and N ∞ is the generalized Nyquist noise formula which reduces to Johnson-Nyquist thermal noise 4 K B TG in the limit of and the quantum zero-point noise 2 ℏ ωG in the limit of. When the protrusion is absent in the junction, transmission functions display rather complex structures: double peaks situating nearly symmetrically away from the Fermi level and a strongly asymmetric profile in the vicinity of the Fermi level are observed for large and small width differences, respectively. On the other hand, a junction with protrusions on both sides of the scattering region shows insulating behaviour near the Fermi level for a large width difference but weak transmission channels are formed at the core of the scattering region for a small width difference. In particular, transport through junctions with a one sided protrusion in the scattering region is always dominated by a Breit–Wigner-type resonance right at the Fermi level, regardless of the large or small width difference. ![]() We show that the width difference between the electrode and the scattering region and the edge protrusion of heterojunctions can be tuned to endow the system's transmission spectrum with distinctive features. We report a first-principles analysis of electron transport through narrow zigzag graphene nanoribbon (up to 2.2 nm) based wedge-shaped heterojunctions. ![]()
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