Probing Concepts in Single-Molecule Wires: Diodes, Electromechanics, FETs, Spinterfaces, etc.

CIC nanoGUNE Seminars

Ismael Diez, University of Barcelona, Barcelona, Spain
nanoGUNE seminar room, Tolosa Hiribidea 76, Donostia - San Sebastian
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Probing Concepts in Single-Molecule Wires: Diodes, Electromechanics, FETs,  Spinterfaces, etc. **Host** : Luis Hueso Single-molecule Junction approaches [1] 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 [6]. 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 [5]. 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 [4]. The last example shows the design of single-molecule field effect transistors (FET) by exploiting an electrochemical gate method [5]. 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 [7] to spin-dependent transport applications [8]. 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. **_References_** [1]. Xu, B., Tao, NJ. _Science_ , **301** (2003) 1221. [2]. Chen, F. _et al._ _JACS_ **128** (2006) 15874. [3]. Díez-Pérez, I. _et al._ _Nature Nanotechnology_ __**6** __ (2011) 226. [4]. Díez-Pérez, I. _et al._ _Nature Chemistry_ **1** (2009) 635. [5]. Díez-Pérez, I. _et al._ _Nature Comm._ **1** (2010) 635. [6]. J. Xia, I. Díez-Pérez, _et al._ _Nano Letters_ **8** (2008) 1960. [7]. Gita Sedghi _et al._ ___Nature Nanotechnology_ **6** __ (2011) 517. [8]. Burzurí, E. _et al._ _Physical Review Letters_ **109** , 147203 (2012).