title: n and p type character of single molecule diodes.
abstract: Looking for single molecule electronic devices, we have investigated the charge transport properties of individual tetra-phenylporphyrin molecules on different substrates by ultrahigh-vacuum scanning tunneling microscopy and spectroscopy and by first-principles calculations. The tetra-phenylporphyrins with a Co atom (Co-TPP) or 2 hydrogens (H2-TPP) in the central macrocycle when deposited on Cu3Au(100) substrates showed a diode-like behavior with p and n type character, respectively. After removing the central hydrogens of H2-TPP molecule with the STM tip an ohmic behavior was measured. The rectifying effect was understood from the theoretical point of view by assuming for Co-TPP HOMO conduction and for H2-TPP LUMO conduction, both selectively elected by the hybridization of states between molecule and substrate surface.
authors: 1] Max Planck Institute of Microstructure Physics, Halle, Germany [2] Laboratório de Filmes Finos e Superfícies, Universidade Federal de Santa Catarina, Florianópolis, Brazil.
authors: Vinícius Claudio
authors: VC
authors: Zoldan
authors: Cryssmat-Lab and Centro NanoMat, Facultad de Química, Universidad de la República, Montevideo, Uruguay.
authors: Ricardo
authors: R
authors: Faccio
authors: Laboratório de Filmes Finos e Superfícies, Universidade Federal de Santa Catarina, Florianópolis, Brazil.
authors: André Avelino
authors: AA
authors: Pasa