Pentacene organic field-effect transistors with polymeric dielectric interfaces: Performance and stability

Low-voltage pentacene organic field-effect transistors (OFETs) with different gate dielectric interfaces are studied and their performance in terms of electrical properties and operational stability is compared. Overall high electrical performance is demonstrated at low voltage by using a 100 nm-thick high-kappa gate dielectric layer of aluminum oxide (Al2O3) fabricated by atomic layer deposition (ALD) and modified with hydroxyl-free low-kappa Polymers like polystyrene (PS), divinyltetramethyldisiloxane-bis(benzocyclobutene) (BCB) (Cyclotene (TM) Dow Chemicals), and as well as with the widely used octadecyl-trichlorosilane (OTS). Devices with PS and BCB dielectric surfaces exhibit almost similar electrical performance with high field-effect mobilities, low subthreshold voltages, and high on/off current ratios. The higher mobility in pentacene transistors with PS can be correlated to the better structural ordering of pentacene films, as demonstrated by atomic force microscopy (AFM) images and X-ray diffraction (XRD). The devices with PS show good electrical stability under bias stress conditions (V-GS = V-DS = -10 V for 1 h), resulting in a negligible drop (similar to 2%) in saturation current (I-DS) in comparison to that in devices with OTS (similar to 12%), and to a very high decay (similar to 30%) for the devices with BCB. (C) 2009 Elsevier B.V. All rights reserved.