PERYLENE-DERIVATIVE LANGMUIR-BLODGETT-FILMS FOR USE AS ULTRATHIN CHARGE-TRANSPORT BARRIERS

Very thin sandwich structures composed of two different perylene-3,4,9,10-tetracarboxyldiimide derivative Langmuir-Blodgett (LB) films, symmetrically contacted with microstructured gold electrodes, have been prepared, The nature of the side chains on the pi-system influences the Langmuir layer behavior and the presence of sulfur appears to increase the ability to withstand the evaporation of the top gold electrode, At. 4 K, both junctions exhibit abrupt current onsets at reproducible voltage thresholds that make these LB layers useful as well-defined tunneling barriers with respect to molecules with lower ionization potential. There is evidence for tunneling processes involving the highest occupied molecular states at low temperatures, whereas increasing temperature leads to the dominance of hopping conductivity.