Electronic structure and ordering of aromatic molecules on Au(111)

Aromatic molecules, such as pentacene, sexiphenyl and naphtho[2,3-a]pyrene, adsorbed on Au(111) surfaces are studied with x-ray photoemission spectroscopy (XPS), ultraviolet photoemission spectroscopy (UPS), temperature programmed desorption (TPD) and scanning tunneling microscopy (STM). All the molecules developed a strong interface dipole indicative of charge transfer from the molecule to the substrate. At monolayer coverages or less a variety of two-dimensional ordered structures were discovered. Naphtho[2,3-a]pyrene, a 2D chrial adsorbate, forms chiral domains rater than a 2D racemic unit cell.