First-principles vs. semi-empirical modeling of global and local electronic transport properties of graphene nanopore-based sensors for DNA sequencing

摘要

Using first-principles quantum transport simulations, based on thenonequilibrium Green function formalism combined with density functional theory(NEGF+DFT), we examine changes in the total and local electronic currentswithin the plane of graphene nanoribbon with zigzag edges (ZGNR) hosting ananopore which are induced by inserting a DNA nucleobase into the pore. We finda sizable change of the zero-bias conductance of two-terminal ZGNR + nanoporedevice after the nucleobase is placed into the most probable position(according to molecular dynamics trajectories) inside the nanopore of a smalldiameter \mbox{$D=1.2$ nm}. Although such effect decreases as the nanopore sizeis increased to \mbox{$D=1.7$ nm}, the contrast between currents in ZGNR +nanopore and ZGNR + nanopore + nucleobase systems can be enhanced by applying asmall bias voltage $V_b \lesssim 0.1$ V. This is explained microscopically asbeing due to DNA nucleobase-induced modification of spatial profile of localcurrent density around the edges of ZGNR. We repeat the same analysis usingNEGF combined with self-consistent charge density functional tight-binding(NEGF+SCC-DFTB) or self-consistent extended H\"{u}ckel (NEGF+SC-EH)semi-empirical methodologies. The large discrepancy we find between the resultsobtained from NEGF+DFT vs. those obtained from NEGF+SCC-DFTB or NEGF+SC-EHapproaches could be of great importance when selecting proper computationalalgorithms for {\em in silico} design of optimal nanoelectronic sensors forrapid DNA sequencing.