Gated lateral charge transport in self-assembled 1-pyrylphosphonic acid molecular multilayers

We have synthesized a p-type organic semiconductor, 1-pyrylphosphonic acid, that can self-assemble onto silicon dioxide to form either a 0.9 nm monolayer or a multilayer with well-defined 2.5 nm step heights depending on the assembly conditions. We allowed polycrystalline multilayers to self-assemble between interdigitated gold electrodes on a SiO₂/Si substrate and measured the charge carrier transport as a function of applied voltages to the electrodes and the gate substrate, temperature, and electrode spacing. At room temperature for channel lengths larger than 400 nm, the conduction was dominated by Poole-Frenkel emission at the metal/molecule interface. At low temperatures (∼240 K) the space charge limited conduction dominated and an on-off ratio of 1000 was achieved. © 2006 American Institute of Physics.