Electrically Stable Self-Assembled Monolayers Achieved through Repeated Surface Exchange of Molecules

Self-assembled monolayers (SAMs) are two-dimensional molecular ensembles. In molecular electronics, SAMs serve as active components for exploring structure-tunneling relationships due to their easy and simple fabrication and atomic-detailed (supra)molecular modifications. Single-component pure SAMs are commonly incorporated into tunneling junctions. However, pure SAMs are defective to some extent, which results in low electrical breakdown voltages and allows access to narrow bias windows through the junctions. Narrow bias windows ultimately limit the possible charge-transport channels to shallow molecular orbital energy levels such as the highest occupied molecular orbital (HOMO) or lowest unoccupied molecular orbital (LUMO), making it difficult to investigate charge transport through deeper molecular orbital (MO) energy levels such as sub-HOMOs and post-LUMOs.