Orbital Interaction Mechanisms of Conductance Enhancement and Rectification by Dithiocarboxylate Anchoring Group

Abstract

We study computationally the electron transport properties of dithiocarboxylate terminated molecular junctions. Transport properties are computed self-consistently within density functional theory and non-equilibrium Green's functions formalism. A microscopic origin of the experimentally observed current amplification by dithiocarboxylate anchoring groups is established. We find that for the 4,4 ′ -biphenyl bis(dithiocarboxylate) junction the interaction of LUMO of the dithiocarboxylate anchoring group with LUMO and HOMO of the biphenyl part results into bonding and antibonding resonances in the transmission spectrum in the vicinity of the electrode Fermi energy. A new microscopic mechanism of rectification is predicted based on the electronic structure of asymmetrical anchoring groups. We show that peaks in the transmission spectra of 4 ′ -thiolatobiphenyl-4-dithiocarboxylate junction respond differently to the applied voltage. Depending upon the origin of a transmission resonance in the orbital interaction picture, its energy can be shifted along with the chemical potential of the electrode to which the molecule is stronger or weaker coupled.

Nature of well-defined conductance of amine-anchored molecular junctions: Density functional calculations

“…Therefore, it is sterically more difficult to get multiple BDA molecules in a junction. Based on this picture, we suggest that the recently studied dithiocarbamate and dithiocarboxylate anchoring groups, 27,28,29 which are even more constrained orientationally, would provide stable and welldefined junctions for experimental measurements.…”

Protonation effects on electron transport through diblock molecular junctions: A theoretical study

“…The electronic transport properties are calculated with the NEGF technique using the ATK package [13,20] , which has been widely used in molecular electronics, showing successes for molecular rectification analysis [9][10][11][12][13][14]21,22] . A molecular junction is divided into three regions, namely, left electrode, contact region, and right electrode.…”

“…However, we note that the relative position of HOMO/LUMO is not directly related to the rectifying effect. An orbital approaching Fermi energy will typically give conductance enhancement, but the rectification is determined by the bias voltage response of the relevant orbitals [9][10][11] .…”

“…Nonequilibrium Green ' s function method (NEGF) and density functional theory (DFT) are widely used to study electron transport in molecular junctions [9][10][11][12][13][14] . The effects of protonation and other electrochemical reactions on molecular conductance were studied previously [15,16] .…”

Theoretical studies on the transport property of oligosilane with p‐n junction

“…Recently, much effort has been devoted to search for other kinds of rectifiers [13][14][15]. One research interest has been focused on the D-p-A molecules, for example, C16H33-Q3CNQ [16,17].…”