Distinct Charge Transport and its Regulation in Single-Molecule and Monolayer Junctions.

As electronic devices miniaturize to the nanometer scale, molecular junctions, including single and monolayer molecules, are gaining attention for applications in logic, storage, and sensing. However, comparative studies of charge transport in these two junction types are limited. Here, a highly conjugated pyrene derivative has been engineered to construct both single-molecule and monolayer junctions. The charge transport within these junctions has been examined systematically through theoretical simulations and electrical measurements. These studies demonstrate a distinct transition in a single molecule from temperature-independent coherent tunneling to temperature-dependent incoherent transport, indicating vibration-mediated transport, while vibration-suppressed coherent transport is observed in a densely packed monolayer. Additionally, anisotropic gating experiments reveal that parallel fields relative to the molecular connection modulate energy levels more efficiently in comparison with perpendicular fields. These findings enrich our understanding of molecular electronic transport and pave the way for diverse developments in the field of molecular electronic devices.