Electronic transport through odd-even methylenic spacers connected to an aromatic ring

Abstract

In this work we propose a theoretical study of charge transport through a nanostructure composed by a methylenic bridge with a phenyl ring at the end, attached between a small silicon cluster in the bottom and a small lead cluster at the top. We use the Non Equilibrium Green Function theory (NEGF-theory) approach, with the electronic structure treated at the density functional theory (DFT) level and model the self energy with the wide band limit approximation. By varying the size of the methylenic bridge from two to five carbons, we show that a geometrical odd–even effect appears in charge transport for cryogenic temperatures, while it is suppressed at room temperature. Such phenomenon was studied by combining MD simulations with ab-initio NEGF transport calculations, thus accounting for the thermal effects. Our theoretical approach reveals the role of avoided-crossing effect on system conductance, occurring only for some alkyl bridge lengths.