Metal-Enhanced Charge Transport and its Mechanism in Atomically Precise Ruthenium Single-Molecule Devices

Achieving reliable, quantitative investigation of charge transport at the single-molecule level remains a key challenge in molecular electronics. In this study, we develop a universal strategy to fabricate molecular devices based on edge-selective chemical oxidation of graphene electrodes with atomically defined zigzag edges and controllable nanogaps, thus enabling precise covalent connection of molecules for device construction. Stable single-molecule devices are then successfully created by covalently connecting three representative wire-like organometallic ruthenium molecules (Ru 1, Ru 2, and Ru 3) between nanogapped graphene electrodes via an amidation reaction. The superior accuracy of our approach is substantiated by the exceptional device-to-device uniformity across various devices, with normalized standard deviations of ∼1.04%, ∼1.27%, and ∼0.91% for Ru 1, Ru 2, and Ru 3, respectively, which significantly surpass conventional methods. Leveraging this platform, we uncover a metal-enhanced conductance effect characterized by an ultralow attenuation (β  =  0.069 nm^{- 1}), arising from strong electrode-molecule covalent coupling. Furthermore, temperature-dependent transport measurements reveal a characteristic barrier-lowering mechanism that modulates charge injection. By enabling accurate investigation of intrinsic molecular transport properties, this study establishes a reproducible and precise experimental platform for developing future functional molecular devices.