We investigate within a coarse-grained model the conditions leading to the appearance of Fano res... more We investigate within a coarse-grained model the conditions leading to the appearance of Fano resonances or anti-resonances in the conductance spectrum of a generic molecular junction with a side group (T-junction). By introducing a simple graphical representation (parabolic diagram), we can easily visualize the relation between the different electronic parameters determining the regimes where Fano resonances or anti-resonances in the low-energy conductance spectrum can be expected. The results obtained within the coarse-grained model are validated using density-functional based quantum transport calculations in realistic T-shaped molecular junctions.
Since the success of the measurement of current conduction through individual molecules, molecula... more Since the success of the measurement of current conduction through individual molecules, molecular electronics has achieved a series of significant advances. Recently the integration of nanotechnology with biological systems has created the opportunity to use bio-recognition for the development of molecule-based devices such as sensitive bio-sensors. In particular, the silicon-organic molecule interface provides a promising platform for the development of such bio-molecule-based molecular devices. I this work, we explore the ...
Charge transport signatures of a carbon-based molecular switch consisting of different tautomers ... more Charge transport signatures of a carbon-based molecular switch consisting of different tautomers of metal-free porphyrin embedded between graphene nanoribbons is studied by combining electronic structure and nonequilibrium transport. Different low-energy and low-bias features are revealed, including negative differential resistance (NDR) and antiresonances, both mediated by subtle quantum interference effects. Moreover, the molecular junctions can display moderate rectifying or nonlinear behavior depending on the position of the hydrogen atoms within the porphyrin core. We rationalize the mechanism leading to NDR and antiresonances by providing a detailed analysis of transmission pathways and frontier molecular orbital distribution.
ABSTRACT One dimensional nanowire field effect transistors (NW-FETs) are a promising platform for... more ABSTRACT One dimensional nanowire field effect transistors (NW-FETs) are a promising platform for sensor applications. The transport characteristics of NW-FETs are strongly modified in liquid environment due to the charging of surface functional groups accompanied with protonation or deprotonation. In order to investigate the influence of surface charges and ionic concentrations on the transport characteristics of Schottky-barrier NW-FETs, we have combined the modified Poisson-Boltzmann theory with the Landauer-Büttiker transport formalism. For a typical device, the model is able to capture the reduction of the sensitivity of NW-FETs in ionic solutions due to the screening from counter ions as well as a local gating from surface functional groups. Our approach allows to model, to investigate, and to optimize realistic Schottky-barrier NW-FET devices in liquid environment.
ABSTRACT Oligo(phenylene ethynylene) is widely used as a molecular conductor in molecular electro... more ABSTRACT Oligo(phenylene ethynylene) is widely used as a molecular conductor in molecular electronics. Phenylene units connected by two carbon–carbon triple bonds at the para position are known to have a low energy barrier (less than 10 kJ/mol) for rotation around the axis of the molecular wire. π orbital localization accompanied with the rotation of the phenylene unit due to the reduction of the π–π coupling strongly influences the electron transport through the molecular wires. Here we demonstrate low-energy conformational gating in oligo(phenylene ethynylene)-based molecular wires connected between contacts. We could achieve an on–off ratio of over 104 by rotating the phenylene units out of the plane of the molecule, which requires only 90 meV in total energy. This result implies that studies of electron transport using stationary geometries may require that special attention be paid to the relationship between molecular fluctuations and conductance.
We investigate within a coarse-grained model the conditions leading to the appearance of Fano res... more We investigate within a coarse-grained model the conditions leading to the appearance of Fano resonances or anti-resonances in the conductance spectrum of a generic molecular junction with a side group (T-junction). By introducing a simple graphical representation (parabolic diagram), we can easily visualize the relation between the different electronic parameters determining the regimes where Fano resonances or anti-resonances in the low-energy conductance spectrum can be expected. The results obtained within the coarse-grained model are validated using density-functional based quantum transport calculations in realistic T-shaped molecular junctions.
Since the success of the measurement of current conduction through individual molecules, molecula... more Since the success of the measurement of current conduction through individual molecules, molecular electronics has achieved a series of significant advances. Recently the integration of nanotechnology with biological systems has created the opportunity to use bio-recognition for the development of molecule-based devices such as sensitive bio-sensors. In particular, the silicon-organic molecule interface provides a promising platform for the development of such bio-molecule-based molecular devices. I this work, we explore the ...
Charge transport signatures of a carbon-based molecular switch consisting of different tautomers ... more Charge transport signatures of a carbon-based molecular switch consisting of different tautomers of metal-free porphyrin embedded between graphene nanoribbons is studied by combining electronic structure and nonequilibrium transport. Different low-energy and low-bias features are revealed, including negative differential resistance (NDR) and antiresonances, both mediated by subtle quantum interference effects. Moreover, the molecular junctions can display moderate rectifying or nonlinear behavior depending on the position of the hydrogen atoms within the porphyrin core. We rationalize the mechanism leading to NDR and antiresonances by providing a detailed analysis of transmission pathways and frontier molecular orbital distribution.
ABSTRACT One dimensional nanowire field effect transistors (NW-FETs) are a promising platform for... more ABSTRACT One dimensional nanowire field effect transistors (NW-FETs) are a promising platform for sensor applications. The transport characteristics of NW-FETs are strongly modified in liquid environment due to the charging of surface functional groups accompanied with protonation or deprotonation. In order to investigate the influence of surface charges and ionic concentrations on the transport characteristics of Schottky-barrier NW-FETs, we have combined the modified Poisson-Boltzmann theory with the Landauer-Büttiker transport formalism. For a typical device, the model is able to capture the reduction of the sensitivity of NW-FETs in ionic solutions due to the screening from counter ions as well as a local gating from surface functional groups. Our approach allows to model, to investigate, and to optimize realistic Schottky-barrier NW-FET devices in liquid environment.
ABSTRACT Oligo(phenylene ethynylene) is widely used as a molecular conductor in molecular electro... more ABSTRACT Oligo(phenylene ethynylene) is widely used as a molecular conductor in molecular electronics. Phenylene units connected by two carbon–carbon triple bonds at the para position are known to have a low energy barrier (less than 10 kJ/mol) for rotation around the axis of the molecular wire. π orbital localization accompanied with the rotation of the phenylene unit due to the reduction of the π–π coupling strongly influences the electron transport through the molecular wires. Here we demonstrate low-energy conformational gating in oligo(phenylene ethynylene)-based molecular wires connected between contacts. We could achieve an on–off ratio of over 104 by rotating the phenylene units out of the plane of the molecule, which requires only 90 meV in total energy. This result implies that studies of electron transport using stationary geometries may require that special attention be paid to the relationship between molecular fluctuations and conductance.
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