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Molecule‐based devices are envisioned to complement silicon devices by providing new functions or by implementing existing functions at a simpler process level and lower cost, by virtue of their self‐organization capabilities. Moreover, they are not bound to von Neuman architecture and this feature may open the way to other architectural paradigms. Neuromorphic electronics is one of them. Here, a device made of molecules and nanoparticles—a nanoparticle organic memory field‐effect transistor (NOMFET)—that exhibits the main behavior of a biological spiking synapse is demonstrated. Facilitating and depressing synaptic behaviors can be reproduced by the NOMFET and can be programmed. The synaptic plasticity for real‐time computing is evidenced and described by a simple model. These results open the way to rate‐coding utilization of the NOMFET in dynamical neuromorphic computing circuits.

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.

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We demonstrate a molecular rectifying junction made from a sequential self-assembly on silicon.The device structure consists of only one conjugated (π) group and an alkyl spacer chain. We obtain rectification ratios up to 37 and threshold voltages for rectification between -0.3V and -0.9V. We show that rectification occurs from resonance through the highest occupied molecular orbital of the π-group in good agreement with our calculations and internal photoemission spectroscopy. This approach allows us to fabricate molecular rectifying diodes compatible with silicon nanotechnologies for future hybrid circuitries.

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International audienceSelf-assembled monolayers (SAMs) are molecular assemblies that spontaneously form on an appropriate substrate dipped into a solution of an active surfactant in an organic solvent. Organic field-effect transistors are described, built on an SAM made of bifunctional molecules comprising a short alkyl chain linked to an oligothiophene moiety that acts as the active semiconductor. The SAM is deposited on a thin oxide layer (alumina or silica) that serves as a gate insulator. Platinum-titanium source and drain electrodes (either top- or bottom-contact configuration) are patterned by using electron-beam (e-beam) lithography, with a channel length ranging between 20 and 1000 nm. In most cases, ill defined current-voltage (I-V) curves are recorded, attributed to a poor electrical contact between platinum and the oligothiophene moiety. However, a few devices offer well-defined curves with a clear saturation, thus allowing an estimation of the mobility: 0.0035 cm2V-1 s-1 for quaterthiophene and 8 × 10-4 cm2V-1 s-1 for terthiophene. In the first case, the on-off ratio reaches 1800 at a gate voltage of -2 V. Interestingly, the device operates at room temperature and very low bias, which may open the way to applications where low consumption is required