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.