Investigation of the electronic transport through photochromic molecules under plasmonic excitation Etudes du transport électronique à travers des molécules photochromes sous excitation plasmonique

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The joint project PlasmoChrom is devoted to the study of electronic transport properties of photoswitchable molecules contacted to metal leads under light irradiation. It is based on the mastering of three hot topics, which are the understanding of electrical transport through metal-molecule-metal junctions, the synthesis of tailored switching molecules, and advanced plasmonics related to the physics of photo-assisted transport. PlasmoChrom will combine these topics in order to reveal how plasmonic resonances can be coupled to metal-molecule-metal devices and thereby aim at enhancing the switching efficiency of photochromic molecules by virtue of optical antenna effects of the electrodes. We will investigate tunable single-molecule junctions with leads patterned with gratings optimized for exciting propagating surface plasmon polaritons (SPPs). In parallel we will nano-assemble two gold nanoparticles connected by a few molecules and investigate by advanced scanning probe techniques how localized surface plasmon resonance (LSPRs) affects the charge transport. For both device concepts the switching efficiency will be studied as a function of plasmonic excitation. These studies will reveal on the one hand a route to optimize the plasmonic properties of the electrodes and, on the other hand, provide guidelines for the improvement of the molecular synthesis and photochromic properties of diarylethene-based molecules. The functionality of diarylethenes is based on the ring-opening/ring-closure principle, which is favorable for device applications because the electronic changes due to the isomerization go along with only minor geometrical changes. The main expected outcome is the design of a molecular electronics device with reproducibly and efficiently tunable conductance.