The adsorption of pentacene molecules on the 2fold surface of the icosahedral (i)AgInYb quasicrystal (QC) has been studied using scanning tunnelling microscopy (STM). The STM images show that the molecules are arranged in rows, and aligned predominantly along the highsymmetry 5fold and 2fold axes of the surface. The row separation perpendicular to the 5fold symmetry axes is either short S = 0.79 « 0.03 nm or long L = 1.24 « 0.02 nm. The ratio between them is close to the golden mean (¸= 1.618+) and creates segments of the Fibonacci sequence. Fourier transform of the scanning tunnelling microscopy (STM) images reveal 2fold, quasicrystalline, longrange order. A comparison of the STM features with the model structure of the substrate shows that Pn molecules adsorb at Yb sites.

We present a study of the adsorption of pentacene (Pn) molecules on the high symmetry (fivefold, threefold, and twofold) surfaces of the icosahedral ( i) Ag–In–Yb quasicrystal. We also compare the results with adsorption of Pn on a surface of a periodic crystal related to this quasicrystal, the (111) surface of the Au–Al–Tb 1/1 approximant. Scanning tunneling microscopy reveals that Pn molecules on the quasicrystal surfaces are aligned along the high symmetry directions of the substrates and selectively adsorb on Yb atoms and thus exhibit quasicrystalline order. Pn molecules on the Au–Al–Tb approximant surface also preferably adopt Tb sites. The behavior of selective adsorption can be understood in terms of the geometry and electronic properties of the adsorbate and substrate. The Yb–Yb (Tb–Tb) separations are comparable to the C–C or H–H distances in a Pn molecule. Pn is an electron donor, whereas the unoccupied electronic states of the substrate are dominated by the rare earth atoms, suggesting that there is an electronic transfer between the Pn molecules and Yb (Tb) atoms.