We describe the growth of a highly ordered pentacene film on the Au(110) surface, investigated in both real and reciprocal space using scanning tunneling microscopy and low-energy electron diffraction techniques. At high coverage, a unidirectional multilayer of π-stacked molecular row is formed with long-range order. Investigations of the interface at low molecular coverage show that this molecular arrangement is a direct consequence of a pentacene-induced surface reconstruction. Pentacene molecules initially adsorb between atomic gold rows of the Au(110)–(1×2) missing row structure and induce a (1×3) surface reconstruction, acting as a template for the organic film formation.

The chemical bonding interactions of molecular pentacene with the Si(100) surface were investigated by high resolution core level photoemission spectroscopy and by scanning tunneling microscopy (STM). Thin films of pentacene were deposited from a thermal evaporator onto the atomically clean Si(100) surface in ultrahigh vacuum. Analysis of the Si 2p core level spectra reveal evidence of a strong chemical interaction between the molecule and the surface. Three chemically shifted components at kinetic energies—0.27, −0.65, and −1.1 eV with respect the bulk peak—are required to consistently fit the Si 2p core level. The −0.27 eV chemically shifted component resulting from the bonding interaction suggests the formation of Si–C bonds between the pentacene and the silicon surface. The other two components are attributed to different adsorption sites on the surface. Annealing the pentacene covered surface in the 100–200 °C temperature range results in the desorption of molecular layers which had been deposited on top of this chemically reacted layer, leaving a monolayer coverage intact. Valence band spectra of the annealed surface indicate that the bonding interaction occurs between the π orbitals of the pentacene and the silicon surface. By acquiring valence band spectra of thicker layers with s and p polarized light it was possible to conclude that the pentacene molecules absorb molecularly on top of the reacted layer with the plane of the molecule lying parallel to the Si(100) surface. The STM studies of submonolayer coverages of pentacene on the clean Si surface allow three distinct molecular orientations to be identified. Adsorption taken place both on top of, and between, the dimer rows with the molecule aligned parallel to the dimer row axis. Molecular adsorption perpendicular to the dimer rows is also observed.

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