Abstract
Large negative differential conductance (NDC) at lower bias regime is a very desirable functional property for single molecular device. Due to the non-conjugated segment separating two conjugated branches, the single thiolated arylethynylene molecule with 9,10-dihydroanthracene core (denoted as TADHA) presents excellent NDC behavior in lower bias regime. Based on the ab initio calculation and non-equilibrium Green’s function formalism, the NDC behavior of TADHA molecular device and the H2O-molecule-adsorption effects are studied systematically. The numerical results show that the NDC behavior of TADHA molecular junction originates from the Stark effect of the applied bias which splits the degeneration of the highest occupied molecular orbital (HOMO) and HOMO-1. The H2O molecule adsorbed on the terminal sulphur atom strongly suppresses the conductance of TADHA molecular device and destroys the NDC behavior in the lower bias regime. Single or separated H2O molecules adsorbed on the backbone of TADHA molecule can depress the energy levels of molecular orbitals, but have little effects on the NDC behavior of the TADHA molecular junction. Aggregate of several H2O molecules adsorbed on one branch of TADHA molecule can dramatically enhance the conductance and NDC behavior of the molecular junction, and result in rectifier behavior.
Highlights
Due to the non-conjugated segment separating two conjugated arms, the single thiolated arylethynylene molecule with 9,10-dihydroanthracene core shows pronounced negative differential conductance (NDC) behavior, which has recent been detected by Perrin et al.[60]
For the H2O molecules being adsorbed on the backbone of TADHA molecule, the aggregate of H2O molecules seems to have stronger influence on the electronic transport properties of TADHA molecular junction than single or separated H2O molecules
Similar to Type II-3 molecular system, the depression of the H2O aggregate destroys the degeneration of the highest occupied molecular orbital (HOMO) and HOMO-1 at zero bias, and splits the high transmission peak at about 0.2 eV (Fig. 6(e))
Summary
Due to the non-conjugated segment separating two conjugated arms, the single thiolated arylethynylene molecule with 9,10-dihydroanthracene core (denoted as TADHA) shows pronounced negative differential conductance (NDC) behavior, which has recent been detected by Perrin et al.[60]. It is significant that Perrin et al fabricated single TADHA molecular junction with large NDC behavior, especially the NDC behavior was occurred at lower bias regime www.nature.com/scientificreports/. By applying non-equilibrium Green’s function (NEGF) formalism, the electronic transport properties of TADHA molecular junction were studied with the influences of H2O adsorbates. The H2O molecules adsorbed on the terminal sulphur atoms destroy the NDC behavior of TADHA molecular device, and depress the current of the molecular junction distinctly at lower bias regime. Our findings are valuable to the fabrication of TADHA molecular junction in solvent, i.e., one can determine whether there are H2O molecules adsorbed on the terminal S atoms or aggregate of H2O molecules adsorbed on the backbone of functional molecule by the electronic transport properties of molecular junction in experiment
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