title: Diode-like I-V characteristics of a nonplanar polyaromatic compound: a spectroscopic study of isolated and stacked dibenzo[g,p]chrysene.
abstract: In this scanning-tunneling-microscopy/spectroscopy study (STM/STS), samples of isolated and close-packed dibenzo[g,p]chrysene (DBC), a nonplanar polyaromatic compound, are used as model systems to demonstrate the effect of intermolecular interactions on the electronic structures. For dropcast films, DBC molecules adopt an edge-on orientation in a close-packed structure on graphite. Isolated DBC molecules are prepared on graphite from a DBC-coated STM tip by a ca. 7 V/10 μs pulse. STS spectra for both isolated- and close-packed DBC molecules exhibit diode-like I-V curves in which the latter shows a turn-on voltage (0.47 V) smaller than that of the former (0.91 V). The diode-like behaviors are attributed to the more-facile tunneling of electrons through the HOMO of DBC than through the LUMO. The reduced turn-on voltage for the films is ascribed to the diminished HOMO-LUMO gap based on the results of DFT (density functional theory) simulations for the energy-level couplings of π-stacked DBC molecules.
authors: Department of Chemistry, National Taiwan University, Taipei 10617, Taiwan.
authors: Shern-Long
authors: SL
authors: Lee
authors: Min-Jie
authors: MJ
authors: Huang
authors: Chun-hsien
authors: CH
authors: Chen
authors: Cheng-I
authors: CI
authors: Wang
authors: Rai-Shung
authors: RS
authors: Liu