Resistive and rectifying effects of pulling gold atoms at thiol-gold nano-contacts

Recent experiments have shown that transport properties of molecular-scale devices can be reversibly altered by the surrounding solvent. Here, we use a combination of first-principles calculations and experiment to explain this change in transport properties through a shift in the local electrostatic potential at the junction caused by nearby conducting and solvent molecules chemically bound to the electrodes. This effect is found to alter the conductance of bipyridine - gold...

The experimental value for the zero bias conductance of organic molecules coupled by thiol-groups to gold electrodes tends to be much smaller than the theoretical result based on density functional theory (DFT) calculations, often by orders of magnitude. To address this puzzle we have analyzed the regime within which the approximations made in these calculations are valid. Our results suggest that a standard step in DFT based transport calculations, namely approximating the e...

Pairs of electrodes with nanometer separation (nano-gap) are achieved through an electromigration-induced break-junction (EIBJ) technique at room temperature. Lithographically defined gold (Au) wires are formed by e-beam evaporation over oxide coated silicon substrates silanized with (3-Mercaptopropyl)trimethoxysilane (MPTMS) and then subjected to electromigration at room temperature to create a nanometer scale gap between the two newly formed Au electrodes. The Si-O-Si coval...

Using an updated simulation tool, we examine molecular junctions comprised of benzene-1,4-dithiolate bonded between gold nanotips, focusing on the importance of environmental factors and inter-electrode distance on the formation and structure of bridged molecules. We investigate the complex relationship between monolayer density and tip separation, finding that the formation of multi-molecule junctions is favored at low monolayer density, while single-molecule junctions are f...

We present the first in a series of microscopic studies of electrical transport through individual molecules with metallic contacts. We view the molecules as ``heterostructures'' composed of chemically well-defined atomic groups, and analyze the device characteristics in terms of the charge and potential response of these atomic-groups to the perturbation induced by the metal-molecule coupling and the applied electrical field, which are modeled using a first-principles based ...

The electronic conductance of a benzene molecule connected to gold electrodes via thiol, thiolate, and amino anchoring groups is calculated using nonequilibrium Green functions in combination with the fully selfconsistent GW approximation. The calculated conductance of benzenedithiol and benzenediamine is five times lower than predicted by standard density functional theory (DFT) in very good agreement with experiments. In contrast, the widely studied benzenedithiolate struct...

Based on density-functional theory calculations, we report a detailed study of the single-molecule charge-transport properties for a series of recently synthesized biphenyl-dithiol molecules [D. Vonlanthen et al., Angew. Chem., Int. Ed. 48, 8886 (2009); A. Mishchenko et al., Nano Lett. 10, 156 (2010)]. The torsion angle {\phi} between the two phenyl rings, and hence the degree of {\pi} conjugation, is controlled by alkyl chains and methyl side groups. We consider three differ...

The effects of water wetting conditions on the transport properties of molecular nano-junctions are investigated theoretically by using a combination of classical molecular dynamics and first principles electronic transport calculations. These are at the level of the non-equilibrium Green's function method implemented for self-interaction corrected density functional theory. We find that water effectively produces electrostatic gating to the molecular junction, with a gating ...

We assess the performances of the transition voltage spectroscopy (TVS) method to determine the energies of the molecular orbitals involved in the electronic transport though molecular junctions. A large number of various molecular junctions made with alkyl chains but with different chemical structure of the electrode-molecule interfaces are studied. In the case of molecular junctions with clean, unoxidized electrode-molecule interfaces, i.e. alkylthiols and alkenes directly ...

The transition from tunneling to metallic contact between two surfaces does not always involve a jump, but can be smooth. We have observed that the configuration and material composition of the electrodes before contact largely determines the presence or absence of a jump. Moreover, when jumps are found preferential values of conductance have been identified. Through combination of experiments, molecular dynamics, and first-principles transport calculations these conductance ...