Low-temperature formation of self-assembled 1,5-diaminoanthraquinone nanofibers: Substrate effects and field emission characteristics

Abstract

In this study, we used thermal evaporation with a low sublimation temperature (42 degrees C) to deposit 1,5-diaminoanthraquinone (DAAQ) in various morphologies-including nanorods, nanocornerstones, and nanofibers-onto various substrates. Three major factors influenced the growth of vertically aligned DAAQ nanofibers on the electrodes: a low water contact angle (WCA) for the substrate and intermolecular hydrogen bonding and pi-pi interactions between the DAAQ molecules. On Au and Ti substrates (low-WCA), the DAAQ nanofibers DAAQ-Au and DAAQ-Ti, respectively, possessed great verticality and high aspect ratios; they also exhibited field emission characteristics, with maximum emission current densities of 0.31 and 0.65 mA/cm(2), respectively, at an applied electric field of 12 V/mu m. The turn-on electric fields for producing a current density of 10 mu A/cm(2) were 8.5 V/mu m for DAAQ-Au and 8.25 V/mu m for DAAQ-Ti. From the slopes of Fowler-Nordheim plots, we calculated the field enhancement factors (beta) of DAAQ-Au and DAAQ-Ti to be 447 and 831, respectively. Field emission stability studies revealed that the DAAQ nanofibers possessed outstanding anti-degrading capability. The emission current did not decrease, but rather increased slightly, after 3000 s. Given the advantages of this simple low-temperature process and the impressive anti-degrading field emission characteristics, such DAAQ nanofibers have great potential for use in various electronics applications (e.g., as organic field emitters). (C) 2011 Elsevier B.V. All rights reserved.