No abstract

A key issue to push molecular devices toward a new range of applications is the ability to master large scale integration while preserving the device’s functionality. Furthermore, providing extra tunability of the device by external parameters, such as gating in a transistor-like configuration, is highly suited for molecular electronics. Large area molecular junctions in crossbar geometry have demonstrated high yields and compatible and compatible fabrication with Complementary Metal Oxide Semiconductor (CMOS) technology. However, such a device’s geometry favors diffusion of metallic atoms in the molecular layer and gives a very limited access to perform electrical or optical gating on molecules. In this work, we propose a new molecular junction architecture going behind these limits. We report a robust approach for the fabrication of molecular junctions based on the electrografting of a nanometer-thick molecular layer in high aspect ratio metallic nanotrenches. Nanotrenches are obtained by edge-mediated shadow deposition, resulting in laterally aligned electrodes with a 10.3 nm ± 3.3 nm average spacing along a 20 μm length. An in-solution electroreduction of diazonium salts is subsequently performed to fill the nanotrenches by a thin oligomeric layer of anthraquinone molecules. Electronic transport measurements performed at room temperature reveal the ability to produce stable molecular devices. Such a new junction’s engineering offers the key advantages of high fabrication yield, great amenability for compact assembly, and reduced leakage current. The proposed architecture opens interesting perspectives to investigate fundamental and applied questions in molecular electronics, in which coupling of the molecules with external stimuli is required.

Transition metal dichalcogenides represent an emergent platform for energy conversion solutions at the nanoscale. The thermoelectric performances of devices based on two-dimensional materials rely not only on the electric and thermal properties of the used materials, but also on device engineering. In actual devices, hybridization effects at the semiconductor/metal interface strongly affect the local band structure with important consequences on charge injection and thermoelectric response. Here, we investigate the role of different metal contacts (Ag, Pd, Co, Ti) on the electric and thermoelectric properties of hBN-supported few layers WSe 2 transistors. In our devices, we reveal a metal contactdependent Seebeck response with high values of the Seebeck coefficient (S), up to ∼ 180 µV/K, and power factors (PF = S 2 σ ) as high as 2.4 µW/cm K 2 (Co), in agreement with the state-of-the-art. Metal electrodes for which weak interface hybridization is theoretically expected (Ag) show the lowest electrical conductivity and the highest Seebeck coefficient. On the opposite, for expected strong interface hybridization (Pd, Co, Ti), electrical conductivity increases and slightly reduced S values are measured. Our work unveils the importance of metal contacts engineering to optimize the thermoelectric performances of actual few layers transition metal dichalcogenides based transistors.