Electronic properties of perfect single crystals of organic semiconductors prepared by crystallization from solutions

Abstract

A chemical method for the preparation of well-defined single crystals of organic semiconductors for organic FET devices is described. Vacuum evaporation has long been used for the preparation of thin films of organic semiconductors such as pentacene. However, nearly perfect single crystals of pentacene and rubrene can also be grown from their solutions. The surface structures of single crystals are investigated by noncontact atomic force microscopy (AFM). Molecularly flat and extremely wide terraces, extending over a width of more than a few micrometers with monomolecular steps, were consistently observed, suggesting that these crystals were nearly perfect single crystals. The molecular packing arrangements of the crystals were revealed by AFM. The hole mobility was also determined by FET characteristics and TOF analysis.