Ordering of a prototypical conjugated molecular system during monolayer growth on the (1 x 2)-Au(110) surface

Adsorption of pentacene on filled d-band metal surfaces: Long-range ordering and adsorption energy

The growth of pentacene on suitable metallic templates is studied by means of low-energy electron diffraction and ultraviolet photoelectron spectroscopy. Highly ordered pentacene single layers can be prepared by deposition on filled d-band metal templates kept at 370 K. The presence of the steps for the Cu(119) vicinal surface and of the Au troughs for the Au(110)-(1 x 2) surface allows the formation of commensurate long-range ordered structures with (3 x 7) and (3 x 6) periodicities, respectively. A detailed analysis of the molecular induced electronic states evolution is performed for different growth morphologies. The adsorption energy of the ordered molecular single layers on the Au(110) surface is lower (1.90 eV) than on the Cu vicinal surface (2.36 eV), where the steps enhance the molecule adsorption energy.

Phase Diagram of Pentacene Growth on Au(110)

We studied the growth of pentacene (C22H14) on the Au(110) surface by means of He atom scattering and Synchrotron X-ray photoemission. We found that two-dimensional commensurate growth only occurs in the monolayer range for a substrate temperature, T(s), higher than approximately 370 K. Larger amounts of deposited molecules forms three-dimensional uncorrelated clusters on the wetting layer. The desorption of second layer molecules occurs at T(s) > or = 420 K. The highest coverage ordered phase displays a (6 x 8) symmetry and corresponds to the saturation coverage at T(s) = 420 K. The (3 x 6) symmetry phase, recently reported for a multilayer planar film [Ph. Guaino, et al. Appl. Phys. Lett. 2004, 85, 2777], is only found at a coverage slightly lower than the (6 x 8) one. The (3 x 6) phase corresponds to the saturation coverage of the first layer at T(s) = 470 K.

Sexithiophene Adlayer Growth on Vicinal Gold Surfaces

We have investigated the initial stages of vacuum-deposited sexithiophene (alpha-6T) adlayer formation on Au(111) vicinal surfaces at room temperature. The in situ scanning tunneling microscopy (STM) and photoemission spectroscopy (PES) reveal a step edge-driven growth of alpha-6T on the Au(111) vicinal surfaces that first leads to the formation of an ordered monolayer, comprising two phases with the molecular major axes aligned along the step edges. The monolayer formation is then followed by the appearance of a single-phase 2D superstructure at a two-monolayer coverage. The results highlight the potential of using vicinal metal surfaces as templates for generating organized organic nanostructures over macroscopic areas for applications in organic electronics and moletronics.