Metallic electrical conduction in alkaline metal-doped pentacene

We have prepared a cesium-doped pentacene film and a rubidium-doped pentacene film and have investigated their electrical properties in order to obtain a new molecular conductive film based on pentacene. It is found that the electrical conductivity depends strongly on the doping temperature. A high electrical conductivity is obtained by annealing of pentacene film doped with the alkaline metal. As a result, the electrical conductivities equal 74 S/cm and 47 S/cm in the cesium-doped pentacene film and in the rubidium-doped pentacene film, respectively. Moreover, we have observed that these conductivities increase with decreasing temperature and show metallic behavior below room temperature. Furthermore, it is found that the electrical resistivity shows anomalous behavior at around 80 K in the cesium-doped pentacene film and at around 90 K in the rubidium-doped pentacene film.