Toward Multiscale Modeling of Carbon Nanotube Transistors

Abstract

Multiscale simulation approaches are needed in order to address scientific and technological questions in the rapidly developing field of carbon nanotube electronics. In this paper, we describe an effort underway to develop a comprehensive capability for multiscale simulation of carbon nanotube electronics. We focus in this paper on one element of that hierarchy, the simulation of ballistic CNTFETs by self-consistently solving the Poisson and Schrödinger equations using the nonequilibrium Green's function (NEGF) formalism. The NEGF transport equation is solved at two levels: i) a semiempirical atomistic level using the pz orbitals of carbon atoms as the basis, and ii) an atomistic mode space approach, which only treats a few subbands in the tube's circumferential direction while retaining an atomistic grid along the carrier transport direction. Simulation examples show that these approaches describe quantum transport effects in nanotube transistors. The paper concludes with a brief discussion of how these semiempirical device-level simulations can be connected to ab initio, continuum, and circuit level simulations in the multiscale hierarchy.