Growth enhancement and field emission characteristics of one-dimensional 3,4,9,10-perylenetetracarboxylic dianhydride nanostructures on pillared titanium substrate

We have utilized the pi-pi interactions between 3,4,9, 1 0-perylenetetracarboxylic dianhydride (PTCDA) molecules and temperature-induced morphology changes to synthesize one-dimensional (ID) nanostructures of PTCDA on a heated (ca. 100 degrees C) titanium substrate through vacuum sublimation. Because of the pillared Ti structures and the presence of reactive Ti-Cl sites, the titanium substrate played a crucial role in assisting the PTCDA molecules to form ID nanostructures. The average diameter of the nanofibers deposited on the Ti-CVD substrate, a Ti substrate formed by chemical vapor deposition (CVD), at 100 degrees C was ca. 84 run, with lengths ranging from 100 nm to 3 mu m. When the PTCDA nanofibers were biased under vacuum, the emission current remained stable. The turn-on electric field for producing a current density of 10 mu A/cm(2) was 8 V/mu m. The maximum emission current density was 1.3 mA/cm(2), measured at 1100 V (E = 11 V/mu m). From the slope of the straight line obtained after plotting ln(J/E-2) versus 1/E, we calculated the field enhancement factor beta to be ca. 989. These results demonstrate the PTCDA nanofibers have great potential for applicability in organic electron-emitting devices. (C) 2007 Elsevier B.V. All rights reserved.