Abstract EN:

This ph-d thesis is about electronic transport through organic molecules inserted in a metal-molecule-metal junction. We describe first a simple process to prepare sub-3 nm gaps by controllable breakage (under an electrical stress) of gold wires lithographed on a sio2/si substrate at low temperature (4. 2 k). We show that the involved mechanism is thermally assisted electromigration. We observe that current-voltage (i-v) characteristics of resulting electrodes are stable up to ~5 v, which gives access to the well-known fowler-nordheim regime in the i-v, allowing an accurate characterisation of the gap size. The average gap is found to be between 1. 5 nm in width and 2. 5 ev in height. Molecules and nanoparticules have then been inserted in the junction. In the case of nanoparticules for example, the resulting i-v clearly shows the suppression of electrical current at low bias, known as coulomb blockade, characteristic of single-electron tunnelling through nanometer-sized structures. Finally we fabricated a single-electron tunneling device based on au nanoparticles connected to the electrodes via terthiophene (t3) molecule. We use the silicon substrate, separated from the planar structure by a silicon oxide of 200 nm, as an electrostatic gate and observed clear current modulation with possible signature of the transport properties of the terthiophene molecules.