Organic thin-film transistors of pentacene films fabricated from a supersonic molecular beam source

Abstract

Top-contact organic thin-film transistors (OTFTs) of pentacene have been fabricated on bare SiO2 and SiO2 modified with hexamethyldisilazane (HMDS) and octadecyltrichlorosilane (OTS). The pentacene films were deposited from a supersonic molecular beam source with kinetic energy of incident molecules ranging from 1.5 to 6.7 eV. The field-effect mobility of OTFTs was found to increase systematically with increasing kinetic energy of the molecular beam. The improvements are more important on HMDS- and OTS-treated surfaces than on bare SiO2. Tapping mode atomic force microscopy images reveal that pentacene thin films deposited at high kinetic energy form with significantly larger grains—independent of surface treatment—than films deposited using low-energy beams.