Two-terminal analog memory comprising self-assembled monolayers of edge-fused porphyrin oligomers

The study of molecular electronic devices displaying hysteresis, non-volatility, and analog switching in their current-voltage characteristics not only reveals fundamental information on electron transfer, but also provides interesting candidates for next-generation computing paradigms. In this work we report on the charge-transport properties of a family of self-assembled monolayer junctions formed from edge-fused porphyrin oligomers (monomer, dimer and trimer). We show that hysteresis emerges as molecular length increases, and that ON-OFF ratios between high and low conductance states reach over 200 for edge-fused porphyrin trimers. By applying voltage sweeps, the junction conductance can be modulated to a series of intermediate conductance states, between the high and low conductance states, that are stable over hour timescales at room temperature.