Composition and sequence-controlled conductance of crystalline unimolecular monolayers

Understanding how the charge travels through sequence-controlled molecules has been a formidable challenge because of simultaneous requirements in well-controlled synthesis and well-manipulated orientation. Here, we report electrically driven simultaneous synthesis and crystallization as a general strategy to study the conductance of composition and sequence-controlled unioligomer and unipolymer monolayers. The structural disorder of molecules and conductance variations on random positions can be extremely minimized, by uniform synthesis of monolayers unidirectionally sandwiched between electrodes, as an important prerequisite for the reproducible measurement on the micrometer scale. These monolayers show tunable current density and on/off ratios in four orders of magnitude with controlled multistate and massive negative differential resistance (NDR) effects. The conductance of monolayer mainly depends on the metal species in homo-metal monolayers, while the sequence becomes a matter in hetero-metal monolayers. Our work demonstrates a promising way to release an ultra-rich variety of electrical parameters and optimize the functions and performances of multilevel resistive devices.

Automated summary

Understanding the charge transport in sequence-controlled molecules has been a challenge due to the need for controlled synthesis and orientation. We demonstrate a general strategy of electrically driven simultaneous synthesis and crystallization to study the conductance of composition and sequence-controlled monolayers. By synthesizing monolayers uniformly between electrodes, structural disorder and conductance variations are minimized, enabling reproducible measurements on the micrometer scale. These monolayers exhibit tunable current density, on/off ratios, multistate behavior, and negative differential resistance effects.