The adsorption of tetracene on a Cu(110) surface has been studied with high-resolution energy loss spectroscopy, low-energy electron diffraction (LEED), and scanning tunneling microscopy (STM). Vibrational spectra confirm that at monolayer (ML) coverage the adsorbed molecules are in a flat-lying geometry with their molecular plane parallel to the substrate. At low coverage, 0.7 ML, LEED shows an oval pattern, which is related to a slightly disordered surface, while STM indicates molecules in different azimuthal orientations. At saturation coverage, a c(10 × 2) structure is formed, which gradually transfers into a p(5 × 2) structure on annealing at 340 K. STM reveals the molecular arrangement within both these unit cells and clearly indicates that the long molecular axis is aligned along 〈110〉. Molecular rows show a long-range wavelike behavior related to the interdigitation of C−H bonds of adjacent molecules. Similar structures, c(12 × 2) and p(6 × 2), are formed for pentacene on Cu(110).

A new, centered orthorhombic crystal, a = 20.7 Å, b = 19.3 Å, c = 3.4 Å, and β = 90 Å, of perylene, C20H12, has been grown epitaxially on a Cu(110) surface under UHV conditions. The crystal structure has been studied with HREELS, LEED, and STM. Vibrational spectra reveal that the molecular planes are parallel to the substrate. Electron diffraction indicates an almost square unit cell in the ab plane in which the a axis is commensurate along the 〈110〉 azimuth of the Cu substrate, while the b axis is incommensurate along the 〈001〉 azimuth. STM images show a large scale smooth morphology of the organic crystal indicative of layer-by-layer growth, while high-resolution images show the details of the centered orthorhombic structure of perylene and the nature of the 3D grain boundaries.

The growth of ordered perylene structures on a Cu(110) surface has been studied by low-energy electron diffraction and scanning tunneling microscopy. Submonolayer STM images show a centered structure with the molecular plane parallel to the substrate. A sequence of STM images indicates molecular diffusion even at room temperature. The monolayer-covered surface shows a c(8 × 4) periodicity, which transfers into a ( ) structure on annealing at 450 K. On further increasing the surface coverage at room temperature, on top of the c(8 × 4) structure, an ordered multilayer structure grows with molecular rows aligned along the 〈110〉 azimuth.