Low-voltage high-performance organic thin film transistors with a thermally annealed polystyrene/hafnium oxide dielectric

Abstract

Low-voltage pentacene-based organic thin film transistors (OTFTs) are demonstrated with polystyrene (PS)/hafnium oxide (HfOx) hybrid dielectrics. Thermal annealing of PS films on HfOx at 120 deg;C (PS-120) induces a flatter orientation of the phenyl groups (tilt angle 65°) at the surface compared to PS films without annealing (PS-RT) (tilt angle 31°). The flatter phenyl group orientation leads to better matching of surface energy between pentacene and PS. Pentacene deposited on PS-120 display higher quality thin films with larger grain sizes and higher crystallinity. Pentacene OTFTs with PS-120/ HfOx hybrid dielectrics can operate at low-voltage (<3V) with high field-effect mobilities (1 cm2 /V s), high on/off current ratios (106), and low subthreshold slopes (100 mV/dec). © 2009 American Institute of Physics.