One-Dimensional Growth of PTCDA Molecular Rows on Si(111)-(2√3 x 2√3)R30°-Sn Surfaces

We report an investigation on the adsorption of 3,4,9,10-perylene tetracarboxylic dianhydride (PTCDA) molecules on Si(111)-(2 root 3 x 2 root 3 )R30 degrees-Sn surfaces using scanning tunneling microscopy (STM) under ultrahigh vacuum. A novel PTCDA structure, consisting of quasi-one-dimensional molecular chains, is obtained at a submonolayer range. A fine balance between intermolecular and molecule-substrate interactions favors and stabilizes the formation of this molecular structure, which extends homogeneously, creating a highly ordered overlayer with regularly spaced rows in a commensurate (4 root 3 x 2 root 3)R30 degrees PTCDA reconstruction. The Visualization of PTCDA molecular orbitals in bias-dependent high resolution STM images allows for identifying the bonding configuration and the molecular adsorption site,