Covalently bonded single-molecule junctions with stable and reversible photoswitched conductivity

Through molecular engineering, single diarylethenes were covalently sandwiched between graphene electrodes to form stable molecular conduction junctions. Our experimental and theoretical studies of these junctions consistently show and interpret reversible conductance photoswitching at room temperature and stochastic switching between different conductive states at low temperature at a single-molecule level.We demonstrate a fully reversible, two-mode, single-molecule electrical switch with unprecedented levels of accuracy (on/off ratio of ∼100), stability (over a year), and reproducibility (46 devices with more than 100 cycles for photoswitching and ∼105 to 106 cycles for stochastic switching).