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In this paper, we report our studies on field effect transistor (FET) THz detectors operating in the non-resonant mode based on the Dyakonov-Shur plasma wave detection theory, where the quantum capacitance dominates. The influence of quantum capacitance in detector response is theoretically developed and numerically simulated at low and high frequencies. Fundamental constraints in the upper frequency limit are also analyzed for FET THz detectors based on various materials, showing advantages of GaN for 8 - 20 THz applications. Experiments at microwave and THz frequencies have been carried out for GaN based devices showing agreement with the theory.

Graphene single electron transistor (SET) as a coulomb blockade (CB) device operates based on the quantum mechanical effect. Its desired current is achieved by overcoming the CB energy that depends on the total capacitance of SET. Therefore, small size of graphene quantum capacitance is suitable for SET structure because it plays a dominant role in the total capacitance. In this paper, the density of state (DOS) model of graphene SET is suggested because of its important effect on many physical properties. Furthermore, carrier concentration as a key factor in quantum capacitance is modeled. Finally, the quantum capacitance of graphene SET based on the fundamental parameters is modeled and compared to the experimental data, so an acceptable agreement between them is reported. As a result, silicon SET can be replaced with graphene SET because of its lower quantum capacitance and also higher operation speed than the silicon one.

Results of research in the quantum capacitance $C_q$ of quasi-2D-crystals are presented. The detected extraordinary behavior of $C_q$ manifests itself in the existence of such energy ranges in which it is practically equal to zero. The causes for the existence of such ranges are: (a) dimensional quantization as a result of the nanoscale of the van der Waals gap, (b) a certain value of the width of the allowed zone in the plane of the layers, which is determined by the value of the effective mass. Intercalation and external electric field are effective factors capable of changing the position of ranges. Thus, in a system connected in a series of electrostatic and quantum capacitances, the resulting capacitance will significantly depend on the $C_q$ behavior. Comparative analyses of structures, chemical bonds, majority of coinciding characteristics of physical quantities in graphite, transition metal dichalcogenides (TMD), and layered crystals A₃B₆ allow us to assert that the obtained qualitative conclusions can be applied for each of them. Calculations of density of states (DOS) of quasi-2D crystals performed by authors within the framework of the improved Kohn–Sham density functional theory (DFT), namely the DFT taking into account the van der Waals forces in it, show a step-like form of DOS qualitatively similar to ours.

Miniaturization of electronic devices carries them to the quantum limits which mean quantum effect will be dominant in nano-size device characterization. A first band analytical model of the quantum capacitance for (16, 0) zig-zag graphene nanoscroll (ZGNS) is presented. The behavior of the quantum capacitance within the degeneracy limits is approximated using the Maxwell–Boltzmann approximation within a range of E - E_F > 3K_BT. The quantum capacitance is subsequently derived from the carrier density of the ZGNS due to its significance within one-dimensional (1D) devices by employing the Taylor's series expansion for parabolic energy band structure approximation. Additionally, the quantum capacitance analytical derivation in term of ZGNS physical form considering the Archimedean spiral-type structure is modeled. Because of its unique geometry structure which provides high area for intercalation, it is expected that ZGNS structure (length and interlayer distances) will alter the quantum capacitance. We also report that at first sub-band of (16, 0) ZGNS the quantum capacitance reach degenerate limit at approximately of ≅ 0.49 × 10^-10F/m @ 49 pF/m.

An atomistic capacitance is derived for a single-wall carbon nanotube in a nano-electromechanical device. Multi-scale calculation is performed using a continuum model for the geometrical capacitance, and statistical and quantum mechanical approaches for the quantum capacitance of the nanotube. The geometrical part of the capacitance is studied in detail using full three-dimensional electrostatics. Results reported in this paper are useful for compact modeling of the electronic and electromechanical nanotube devices.

In this paper, study on the capacitive effects of Graphene nanoribbon (GNR) in VLSI interconnect has been studied as a function of GNR width, Fermi function and gate voltage. The quantum capacitance of GNR has been simulated in terms of Fermi function for three different values of insulator thickness — 1.5nm, 2nm and 2.5nm. After that, quantum capacitance is studied in both degenerate and nondegenerate region with respect to Fermi function and gate voltage of range 1–5V. Then, the total capacitance of GNR is studied as a function of gate voltage of $-2$–5V range at degenerate and nondegenerate regions, where width of GNR is considered 4nm. Finally, the total capacitance of GNR is studied in both regions with varying GNR width, considering fixed gate voltage of 3V. After analyzing these simulations, it has been found that GNR in degenerate region shows nearly steady capacitance under a certain applied gate voltage.

We study the quantum capacitance $C_q$ in the objects with completely discrete structure of electron states as a result of both dimensional quantization and applied magnetic field. The capacitance is analyzed in such objects as nanoplates of metal, semiconductor and semimetal. Factors which define the form of the dependence of $C_q$ on the position of the Fermi level or potential bias, and magnetic field, are analyzed.

This work presents a comprehensive investigation of the quantum capacitance and the associated effects on the carrier transit delay in armchair-edge graphene nanoribbons (A-GNRs) based on semi-analytical method. We emphasize on the realistic analysis of bandgap with taking edge effects into account by means of modified tight binding (TB) model. The results show that the edge effects have significant influence in defining the bandgap which is a necessary input in the accurate analyses of capacitance. The quantum capacitance is discussed in both nondegenerate (low gate voltage) and degenerate (high gate voltage) regimes. We observe that the classical capacitance limits the total gate (external) capacitance in the degenerate regime, whereas, quantum capacitance limits the external gate capacitance in the nondegenerate regime. The influence of gate capacitances on the gate delay is studied extensively to demonstrate the optimization of switching time. Moreover, the high-field behavior of a GNR is studied in the degenerate and nondegenerate regimes. We find that a smaller intrinsic capacitance appears in the channel due to high velocity carrier, which limits the quantum capacitance and thus limit the gate delay. Such detail analysis of GNRs considering a realistic model would be useful for the optimized design of GNR-based nanoelectronic devices.