Temperature and gate voltage dependent transport across a single organic semiconductor grain boundary

Temperature and gate voltage dependent transport measurements on single grain boundaries in the organic semiconductor sexithiophene (6T) are described. Isolated grain boundaries are formed by vacuum deposition of pairs of 6T grains between Au electrodes 1.5–2.0 μm apart on SiO2/Si substrates; grain boundary formation is monitored using atomic force microscopy. The Si substrate serves as the gate electrode. We show from the activation energy, threshold voltage, and field effect resistance of the grain boundary junction that carrier transport is limited by the grain boundary. The activation energy of room temperature transport is of the order of 100 meV at carrier densities of ∼1018 cm−3 and decreases with increasing carrier concentration (gate voltage). We also observe that longer grain boundaries with smaller misorientation angles result in larger currents through a grain boundary. We relate our data to two models, one that assumes acceptor-like traps localized at a grain boundary and another that assumes...