"Probing Concepts in Single-Molecule Wires: Diodes, Electromechanics, FETs, Spinterfaces, etc."
Who: Ismael Diez, University of Barcelona, Barcelona, Spain
Place: nanoGUNE seminar room, Tolosa Hiribidea 76, Donostia - San Sebastian
Date: Monday, 9 June 2014, 11:00
Host: Luis Hueso
Single-molecule Junction approaches  have advanced the comprehension of charge transport in a large variety of molecular backbones and brought fine details on the molecule-electrode communication [2,3]. Latest efforts in this field have been focused on the design of nanoscale molecular contacts with new electrical functionalities [4,5].
The first block of this seminar will describe our latest implemented methodologies to univocally identify the formation of single-molecule contacts between two metal beads. The methods are based on the combination of DC-AC current detection schemes when a small AC mechanical perturbation is introduced along the main single-molecule junction axis .
For the second block, we have picked few examples that illustrate the exploitation of previous methodologies to tailor single-molecule wires with new electrical behaviors. The first case presents an example of controlling diode (rectification) behavior in a single-molecule device . Here we demonstrate that it is possible to go from a perfectly symmetric to a highly rectifying charge transport in a single-molecule junction by introducing specific asymmetry within the molecular backbone. The second case shows an example of a single-molecule device incorporating mechanical gating capabilities . The last example shows the design of single-molecule field effect transistors (FET) by exploiting an electrochemical gate method . Several examples of efficient current modulation on single-molecule contact with this approach will be shown.
Last block of this seminar will focus on single-molecule wires built with more complex organometallic backbones. Such molecular systems brought a number of potential applications in nanoscale electrical interfaces, from highly efficient molecular wires  to spin-dependent transport applications . Two new examples will be brought here: first, spin-dependent transport in a single-molecule contact built with an Fe(II)-based spin crossover (SCO) compound is presented. Large magnetoresistance (>100%) is observed at low applied biases depending upon the magnetization direction of a Ni electrode. The second example illustrates the use of the metal coordination chemistry to wire a single metalloporphyrin ring between two metal electrodes in a fully flat conformation. This special geometry allows enhanced electrical coupling between the metal electrodes and the molecule through the porphyrin metal center.
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