A new azobenzene-thiophene molecular switch is designed, synthesized, and used to form self-assembled monolayers (SAM) on gold. An "on/off" conductance ratio up to 7 x 10(3) (with an average value of 1.5 x 10(3)) is reported. The "on" conductance state is clearly identified to the cis isomer of the azobenzene moiety. The high on/off ratio is explained in terms of photoinduced, configuration-related changes in the electrode-molecule interface energetics (changes in the energy position of the molecular orbitals with respect to the Fermi energy of electrodes) in addition to changes in the tunnel barrier length (length of the molecules). First principles density functional calculations demonstrate a better delocalization of the frontier orbitals as well as a stronger electronic coupling between the azobenzene moiety and the electrode for the cis configuration over the trans one. Measured photoionization cross sections for the molecules in the SAM are close to the known values for azobenzene derivatives in solution.

Immobilization of an azobenzene-bithiophene compound on a gold surface leads to self-assembled monolayers with photoswitchable electrical properties.

We report on hybrid memristive devices made of a network of gold nanoparticles (10 nm diameter) functionalized by tailored 3,4-(ethylenedioxy)thiophene (TEDOT) molecules, deposited between two planar electrodes with nanometer and micrometer gaps (100 nm to 10 μm apart), and electro-polymerized in situ to form a monolayer film of conjugated polymer with embedded gold nanoparticles (AuNPs). Electrical properties of these films exhibit two interesting naphthalenethiol 8 or with 1-dodecanethiol 9 , a perylene derivative with Au nanoparticles 10 , pentacene films with embedded Au nanoparticles 11;12 . Some of these previous reports claimed, in addition to resistive switching, the observation of a Negative Differential Resistance (NDR) in the device. 3;5;6 However in these previous works, devices have a vertical sandwich structure consisting in a metal/switching layer/metal stack where the hybrid material is localized between top and bottom electrodes. In these devices two approaches were used to form the hybrid material: (i) by mixing the organic material with the nanoparticles in solution and depositing the blend by spincoating on the surface; or (ii) by evaporation of an ultra-thin metallic layer (usually 5 nm) onto the organic layer in order to form metal clusters or nanoparticles 13 . Furthermore, resistive memories and their extension to memristive systems have opened new routes toward innovative computing solutions such as logic-in-memory (implication logic with memristor) 14 , analog computing (threshold logic with memristor 15 ) or neuromorphic computing 16 .Nevertheless, to become attractive, these different approaches require a massive integration of memory elements. If crossbar integration consisting in vertical devices interconnected between metallic lines and columns has been considered as an interesting solutions, its practical realization with standard lithographic technics (i.e. top-down approaches) is facing severe limitations such as wire resistance contribution, crosstalk of memory elements during programming and sneak path during reading. One relatively unexplored solution is to rely on bottom-up approaches based on randomly assembly elements, in which memory functionalities are configured post-fabrication.This idea was initially proposed with the concept of nanocell 17;18;19 but remains in its early steps of development from a practical viewpoint and would benefit from functional and reliable hardware for its implementation.Here, we report on a hybrid organic/gold nanoparticle memory with several advances compared to the devices demonstrated until now: (i) a nanoscale -monolayer thick-planar structure: the hybrid organic/gold nanoparticle material is placed between two coplanar electrodes with characteristic distance smaller than 100 nm; (ii) a bottom-up approach for material synthesis, device fabrication and operation: redox ligands were electro-polymerized in situ (i.e. into the device) to form a monolayer of a conjugated polymer with embedded Au nanoparticles and the memory functionality is def...