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With the atomistic Kubo–Verges method we calculate the ballistic conductance of various conformers of DNA (A,B,Z), as well as intermediate and composite conformations, using experimental structures and model complexes. For duplexes with 6 and 15 base pairs, we find that the valence band conductivity near the Fermi edge varies dramatically between the different conformations, most notably for the B-to-Z transition. The latter conductivity differences are largely unchanged both in the presence and in the absence of trimethylthiol linkers between DNA and gold electrodes in vacuo, but become much less drastic when explicit molecular dynamics and water-counterion surrounding of B- and Z-DNA are taken into account. Based on atomistic structural models, we argue that changes in the electrostatic energy in the presence of an applied external electric field can induce conformational switching that may be exploited in novel DNA-based memory devices of high packing density. [ABSTRACT FROM AUTHOR]

A simple model of negative capacitance (NC) MOSFETs is presented. The model treats 2-D electrostatic effects, and the ballistic to diffusive transport regimes. It shows quantitative agreement with numerical device simulations based on a self-consistent solution of the Poisson equation and quantum transport equation based on nonequilibrium Green’s function formalism, for an NC MOSFET structure without an internal floating gate. The model can accurately describe the reverse drain-induced barrier lowering (DIBL) and negative output differential conductance (NDC) effects as the NC FETs scale down. With approximations valid at low power supply voltages, it is shown that the improvement of the subthreshold swing (SS) due to electrostatic short channel effects results in a linear increase of the reverse DIBL and NDC. For a modified NC MOSFET structure with an ultrathin quantum metallic layer contacted to the source, the SS, however, can be improved considerably with the reverse DIBL and NDC approximately unchanged. [ABSTRACT FROM PUBLISHER]

We have already presented a compact model for FETs operating in the quasi-ballistic regime [1]. However, this model suffers from two important problems: 1) the profile for charge density along the channel is not correctly accounted for and 2) current is not conserved throughout the channel. In this brief, we propose improvement, which does away with these inaccuracies. [ABSTRACT FROM AUTHOR]

In this paper, we present an analytical semiempirical model of the profile of the channel charge and potential in quasi-ballistic double-gate (DG) MOSFETs. The charge model is based on the premise of separating the charge density in the quasi-ballistic channel into two hypothetical components: 1) exclusively ballistic (collision-free) and 2) collision-dominated components, which are governed by the same electrostatics. These components are related to each other through a ballisticity parameter whose values lie between 0 and 1. Varying the value of this parameter allows us to model the charge profile continuously between diffusive and purely ballistic devices. Using the proposed charge model and the DG MOSFET electrostatics, an analytical expression for the channel potential is derived which, like the charge model, is continuous between the diffusive and ballistic regimes. [ABSTRACT FROM AUTHOR]