Characterization of molecular overlayers on metal surface in dynamic equilibrium by scanning tunneling microscope H.Suzuki,S.Berner,M.Brunner,H.Yanagi,D.Schlettwein,T.A.Jung,H-J.Guentherodt Abstract: The overlayer structure of [tetra-(3,5-di-tertiary-butylphenyl)porphyrinato] copper (Cu-TBPP) molecules on Ag (001) and chloro(subphthalocyaninato)boron(III) (SubPc) molecules on Ag (111) were analyzed by UHV scanning tunneling microscope. In the case of approximately 20% coverage, both molecules show high mobility on the substrates, that cause to form their overlayer island on terraces. Cu-TBPP molecules form oblique lattice on Ag (001) surface and SubPc molecules forms hexagonal lattice on Ag (111). In high-resolution STM image of the overlayer, characteristic protrusion corresponding to the molecular shapes, such as four-lobes of Cu-TBPP and three-lobes of SubPc, were clearly identified.