Carrier statistics and quantum capacitance models of graphene nanoscroll

As a new category of quasi-one-dimensional materials, graphene nanoscroll (GNS) has captivated the researchers recently because of its exceptional electronic properties like having large carrier mobility. In addition, it is admitted that the scrolled configurations for graphene indicate larger stability concerning the energy, as opposed to their counterpart planar configurations like nanoribbon, nanotube, and bilayer graphene. By utilizing a novel analytical approach, the current paper introduces modeling of the density of state (DOS), carrier concentration, and quantum capacitance for graphene nanoscroll (suggested schematic perfect scroll-like Archimedes spiral). The DOS model was derived at first, while it was later applied to compute the carrier concentration and quantum capacitance model. Furthermore, the carrier concentration and quantum capacitance were modeled for both degenerate and nondegenerate regimes, along with examining the effect of structural parameters and chirality number on the density of state and carrier concentration. Latterly, the temperature effect on the quantum capacitance was studied to

Analytical modeling of the sensing parameters for graphene nanoscroll-based gas sensors

Graphene nanoscrolls (GNSs) as a new category of quasi one-dimensional (1D) belong to the carbon-based nanomaterials, which have recently captivated the attention of researchers. The latest discoveries of outstanding characteristics of GNSs in terms of structural and electronic properties such as high mobility, controllable band gap, and tunable core size. Previous studies have shown the fact that graphene different structures such as carbon nanotube (CNT), bilayer graphene (BLG) and GNS experience changes in the electrical conductivity when expose to various gases. Therefore, these materials are proposed as a promising candidate for gas detection sensors. These are typically constructed on a field effect transistor (FET) based structure in which the GNS is employed as the channel between the source and the drain. In this study, an analytical model has been proposed and developed with the initial assumption that the gate voltage is directly proportional to the gas concentration as well as its temperature. The effect of gas adsorption on GNS surface makes the changes in GNS conductance which leads to the changes in the current of sensor consequently. This phenomenon is considered as sensing mechanism with proposed sensing parameters. Using the corresponding formula for GNS conductance, the proposed mathematical model is derived. Also, artificial neural network (ANN) algorithms have also been incorporated to obtain other models for the current-voltage (I-V) characteristic in which the analytical data extracted from current and previous related works has been used as the training data set. The comparative study of the results from ANN and the analytical models with the experimental data in hand shows a satisfactory agreement which validates the proposed models

Graphene nanoribbon field-effect transistor at high bias

Combination of high-mean free path and scaling ability makes graphene nanoribbon (GNR) attractive for application of field-effect transistors and subject of intense research. Here, we study its behaviour at high bias near and after electrical breakdown. Theoretical modelling, Monte Carlo simulation, and experimental approaches are used to calculate net generation rate, ionization coefficient, current, and finally breakdown voltage (BV). It is seen that a typical GNR field-effect transistor's (GNRFET) breakdown voltage is in the range of 0.5 to 3 V for different channel lengths, and compared with silicon similar counterparts, it is less. Furthermore, the likely mechanism of breakdown is studied

Analytical model for threshold voltage of double gate bilayer graphene field effect transistors

A new model for threshold voltage of double-gate Bilayer Graphene Field Effect Transistors (BLG-FETs) is presented in this paper. The modeling starts with deriving surface potential and the threshold voltage was modeled by calculating the minimum surface potential along the channel. The effect of quantum capacitance was taken into account in the potential distribution model. For the purpose of verification, FlexPDE 3D Poisson solver was employed. Comparison of theoretical and simulation results shows a good agreement. Using the proposed model, the effect of several structural parameters i.e. oxide thickness, quantum capacitance, drain voltage, channel length and doping concentration on the threshold voltage and surface potential was comprehensively studie

Analytical study of subthreshold behaviour of double gate bilayer graphene field effect transistors

In this paper, several analytical models have been developed for 2-D potential distribution, subthreshold current, drain induced barrier lowering (DIBL), and subthreshold-slope (SS) to study the subthreshold behaviour of bilayer graphene filed effect transistors (BLG-FETs). The models are grounded on the basis of the exact solution of the two-dimensional Poisson's equation while the quantum capacitance effect has been considered throughout the models. The accuracy of the potential distribution model is verified by its analytical results that agree well with those of the FlexPDE Poissons equation solver program. In addition, the effects of the channel length, the oxide thickness, quantum capacitance, and gate biases on subthreshold parameters of BLG-FETs have been explored and the results are compared with those of the silicon FET

Structural and properties of graphene nanobelts rolled up into spiral by a single graphene sheet

Graphene nanobelts (GNBs) as a new class of quasi two dimensional materials that have attracted much research interest in the last few years. Nanobelts are known to show excellent field emission characteristics. On the other hand the scrolled configurations such as graphene nanobelts configuration indicate more stable (in terms of energy) than their equivalent planar configurations such as nanoribbon, nanotube. In this article, modelling of nanobelts (proposed schematic of nanobelts perfect scroll-like Archimedean spirals) energy band structure and bandgap dependency on chiral vector (C) over right arrow and length of nanobelts (L) (structural parameter) is reported. The third nearest-neighbour binding analysis is used to derive energy ban structure model of GNBs. Our results show that the effect of structural parameters and chirality number have great influence on bandgap. In addition the critical values of L and chiral number as important factors in order to illustrate electronic structures and properties of GNBs are investigated