.gif)
The organic semiconductor pentacene, has attracted considerable attention due to its relative high hole mobility of 3 cm2/Vs at room temperature and above 100,000 cm2/Vs at lower temperature. Before pentacene can show its exciting properties, like ambipolar transport, integer and fractional quantum Hall effects or superconductivity at 2 K, it has to be separated from the smallest traces of impurities. Using gas phase transport in a stream of carrying gas, it is possible to separate pentacene (deep dark blue crystals not seen on this photo) from the very similar to pentacene compound, dihydropentacene. Under proper conditions, dihydropentacene co-crystallizes with pentacene forming well oriented layers inside pentacene crystals. The crystals on the cover are in fact co-crystals of the organic semiconductor pentacene and its insulating impurity dihydropentacene.