Formation of an ordered Cu-phtalocyanine molecular layer on a pyrolytic graphite surface

A Cu-phtalocyanine sub-monolayer prepared on a highly ordered pyrolytic gra phite surface by means of deposition from solution at liquid/solid interfac e was investigated by scanning tunneling microscopy. The deposited layer is formed by flat lying Cu-phtalocyanine molecules and it has a triangle stru cture with 2.56 nm average period. The layer represents a (6 root3 x 6 root 3) superstructure rotated by 30 degrees relatively to the graphite surface triangle unit cell. A relatively weak interaction of the Cuphtalocyanine mo lecules with the substrate was observed. An increase of the surface potenti al (about 0.05 eV) was registered during vacuum deposition of Cu-phtalocyan ine molecules on the graphite substrate by means of Electron spectroscopy. The formation of the CuPc monolayer is discussed in terms of interaction be tween the molecules and the solvent and the graphite substrate.