The transition from surface to bulk pentacene at the Au(111) interface will have important implications for the mechanism of carrier transport across the interface. STM observations of pentacene molecules on the Au(111) surface, at more than a monolayer coverage, revealed periodic rows of molecules spaced 61 ± 5 Å apart. These widely spaced periodic rows consist of flat and edge-on molecules aligned with the initial layer of pentacene. Commensuration with the surface and characteristic bulk pentacene−pentacene interactions drive the formation of this unique structure.

The adsorption of the two-dimensionally chiral naphtho[2,3-a]pyrene molecule has been studied on Au(111). Both structural and electronic properties of the naphtho[2,3-a]pyrene (NP)/Au(111) interface have been measured. Ultraviolet and X-ray photoelectron spectroscopy have been employed to measure the energies of the molecular orbitals of the NP film with respect to the gold Fermi level. A Schottky junction with a large interface dipole (0.99 eV) is formed between Au(111) and NP. Temperature-programmed desorption was used to determine that adsorbed NP has a binding energy of 102.2 kJ/mol. Chiral domains have been observed with scanning tunneling microscopy due to the spontaneous phase separation of the 2-D enantiomers. Two distinct structural polymorphs have been observed, one of which has homochiral paired molecular rows. Models of the 2D structure are proposed that are in excellent agreement with experimental measurements.

Several electrochemically active polypyridine-metal complexes are isolated in the formally zero-charged state via reductive electrocrystallization, and are thermally evaporated to form conducting thin films with low work functions. Solution-phase cyclic voltammetry of the parent complexes is used to predict the work function of these materials. The reduced films are used as cathode materials in organic light-emitting devices, in place of the commonly used low work function metals such as calcium and aluminum. These reduced complexes represent a new class of materials available for use as electron-injecting contacts in organic electroluminescent devices.

Nanostructures were fabricated on natural MoS 2 crystals by bombardment with low doses of Ar + and He + with energies ranging from 100 to 5 keV. The bombarded surfaces were investigated with x-ray photoemission spectroscopy ͑XPS͒ and scanning tunneling microscopy ͑STM͒ in an ultrahigh vacuum environment. The ion exposures were low enough to ensure that the observed nanostructures can be associated with individual ion impacts. Argon ions ͑Ar + ͒ with energies of 100 eV or less remove very few, if any, sulfur atoms from the surface but STM and XPS studies reveal that the electronic structure of the MoS 2 surface is altered. Ar + with energies greater than 100 eV has a higher probability of sputtering sulfur atoms from the surface. The apparent size of the nanostructures in the STM images increased with Ar + energies up to about 1 keV and was dependent on the angle of incidence of the Ar + . Helium ion ͑He + ͒ sputtering of MoS 2 produced similar but smaller nanostructures when compared to Ar + at the same impinged ion energy. STM images showed bright ring-shaped features were created with He + energies greater than 500 eV. On the basis of XPS and current imaging tunneling spectroscopy investigations, the features are assigned to sulfur atom vacancies. A change in the surface doping type from n to p was observed upon light sputtering of the surface.