Two-State, Nonvolatile Memristors and Light-Assisted Logic-In Operation from Diarylethene-Based Single-Molecule Junctions

Single-molecule junctions (SMJs) were fabricated incorporating photochromic diarylethene units, which are covalently bonded to a bottom electrode by diazonium electro-reduction. The scanning-tunneling-microscopy break-junction (STM-BJ) and conductance versus time (STM-<i>G</i>(<i>t</i>)) techniques characterize the different conductance states upon light irradiation, whereas the STM current versus voltage (<i>I</i>/<i>V</i>) measurement at room temperature allows electric-field-stimulated conductance switching. We observe that the Au-[DAE]₁-Pt SMJs appear with a single conductance state. The Au-[DAE]₂-Pt SMJs show two distinct high- and low-conductance states under UV or visible light irradiation. Most importantly, hysteresis <i>I</i>/<i>V</i> loops, emerging with a yield as high as 60%, reveal an electric-field-generated conductance switching with a memory effect. Cycles of successive "reading, writing, and erasing" processes are practiced at different applied voltages between the "0" (LC) and "1" (HC) states such that a Au-[DAE]₂-Pt SMJ functions as a fully electric nonvolatile memristor. Statistical <i>I</i>/<i>t</i> and <i>I</i>/<i>V</i> heatmaps indicate that the memory properties are highly reproducible. Considering light and electric-field stimulus as two different inputs and the resulting HC or LC as output signals, the Au-[DAE]₂-Pt memristor shows an XOR logic-in operation.