Fano Factor in Strained Graphene Nanoribbon Nanodevices

Abstract

We investigate the Fano factor in a strained armchair and zigzag graphene nanoribbon nanodevice under the effect of ac field in a wide range of frequencies at different temperatures (10 K–70 K). This nanodevice is modeled as follows: a graphene nanoribbon is connected to two metallic leads. These two metallic leads operate as a source and a drain. The conducting substance is the gate electrode in this three-terminal nanodevice. Another metallic gate is used to govern the electrostatics and the switching of the graphene nanoribbon channel. The substances at the graphene nanoribbon/metal contact are controlled by the back gate. The photon-assisted tunneling probability is deduced by solving the Dirac eigenvalue differential equation in which the Fano factor is expressed in terms of this tunneling probability. The results show that for the investigated nanodevice, the Fano factor decreases as the frequency of the induced ac field increases, while it increases as the temperature increases. In general, the Fano factors for both strained armchair and zigzag graphene nanoribbons are different. This is due to the effect of the uniaxial strain. It is shown that the band structure parameters of graphene nanoribbons at the energy gap, the C–C bond length, the hopping integral, the Fermi energy and the width are modulated by uniaxial strain. This research gives us a promise of the present nanodevice being used for digital nanoelectronics and sensors.

Certain Aspects of Quantum Transport in Zigzag Graphene Nanoribbons

“…As shown in Figure 1, the electron confined in region (II) behaves as a quantum dot. Generally, conductance is expressed in terms of tunneling probability, which is defined as the ratio of the flux of a transmitted wave to that of an incident wave [51,60]. The tunneling probability depends on the applied potential, the energy of the electron, and the width of the quantum well [60].…”

“…For instance, shot noise measurements can be used to show the fermionic character of electrons, currentcarrying by fractional charges, and to investigate many-body phenomena in mesoscopic physics [50]. Shot noise is absent in macroscopic metallic resistors since electron-phonon interaction smooths out current fluctuations [51]. It is not very significant at high currents and longer time scales, but it becomes notable at the nanoscale.…”

“…It is not very significant at high currents and longer time scales, but it becomes notable at the nanoscale. Many solid-state devices exhibit these time-dependent current fluctuations caused by the discrete nature and restricted transmission of the electric charge, e.g., tunnel junctions, p-n junctions, and Schottky barrier diodes [51]. Shot noise has also been calculated in the case of GNRs [45,[52][53][54].…”

“…Shot noise has also been calculated in the case of GNRs [45,[52][53][54]. The Fano factor (F), which indicates the strength of the noise power density, depends on the frequency of the applied field, temperature, and presence of disorder in graphene [51]. It is defined as the ratio of noise current to mean current and gives valuable information about electronic transport [51].…”

“…The Fano factor (F), which indicates the strength of the noise power density, depends on the frequency of the applied field, temperature, and presence of disorder in graphene [51]. It is defined as the ratio of noise current to mean current and gives valuable information about electronic transport [51]. The Fano factor is also defined by the ratio of its variance to its mean.…”