Effect of scattering and contacts on current and electrostatics in carbon nanotubes

Abstract

We computationally study the electrostatic potential profile and current carrying capacity of carbon nanotubes as a function of length and diameter. Our study is based on solving the non equilibrium Green's function and Poisson equations self-consistently, including the effect of electronphonon scattering. A transition from ballistic to diffusive regime of electron transport with increase of applied bias is manifested by qualitative changes in potential profiles, differential conductance and electric field in a nanotube. In the low bias ballistic limit, most of the applied voltage drop occurs near the contacts. In addition, the electric field at the tube center increases proportionally with diameter. In contrast, at high biases, most of the applied voltage drops across the nanotube, and the electric field at the tube center decreases with increase in diameter. We find that the differential conductance can increase or decrease with bias as a result of an interplay of nanotube length, diameter and a quality factor of the contacts. From an application view point, we find that the current carrying capacity of nanotubes increases with increase in diameter. Finally, we investigate the role of inner tubes in affecting the current carried by the outermost tube of a multiwalled nanotube.

Impact of phonon scattering in Si/GaAs/InGaAs nanowires and FinFets: a NEGF perspective

“…The neglect of the real part produces an underestimate of the electron density in the channel of the transistor; this fact has been pointed out by A. Svizhenko [12]. Similar effects have been observed by other authors [11,13]. Ignoring the real part produces an underestimate of mobility at low inversion charges [14].…”

“…Only a handful of authors consider full self-energy [11][12][13][14] as the calculation of the real part (or the renormalization of the levels due to electron phonon scattering) needs the computation of the Hilbert transform [15], which is very time-consuming. In addition, the conservation of the density of states requires the real as well as the imaginary part of the self-energy [17].…”

Role of contact bonding on electronic transport in metal–carbon nanotube–metal systems

“…Finally we note that, although we concentrate our attention on the contact effects over the transport features (which should be important when small size CNTs are considered), we are aware that other scattering (electron-phonon, electron-electron) mechanisms can strongly influence the conductance of these systems [14]. Future extensions of this work will be devoted to address the problem of a realistic and reliable modelling of both scattering and contacts in CNT based systems.…”

Modeling of Carbon Nanotube Field Effect Transistors

“…A number of groups have reported modeling and simulation studies of CNTFETs [43][44][45][46][47][48]. Our intent in this section is not to review that works.…”