Adsorption behavior of iron phthalocyanine at the initial stage on Cu(100) surface

The adsorption behavior of iron phthalocyanine (FePc) on the Cu(100) surface at the initial stage has been investigated by combining scanning tunneling microscopy (STM) and density functional theory (DFT) calculations. At low coverage, FePc molecules deposited on the sample surface at room temperature tend to adsorb dispersedly with their molecular planes parallel to the crystallographic directions of the substrate. Another interesting STM observation for the sub-monolayer coverage is that the molecular axes of FePc are aligned along [037] (as well as 03¯7) azimuth. At the monolayer coverage and elevated temperature, two types of ordered structures are observed. The FePc adsorption sites for the experimentally observed two distinct ordered domains have been revealed through DFT calculations. With further increasing the coverage, molecular clusters are formed particularly near the step edges. ► FePc on Cu(100) from submono- to multilayer has been studied. ► At very low coverage, FePc molecules tend to adsorb dispersedly with their molecular planes parallel to the substrate. ► Ordered molecular structures can only be achieved at elevated temperature. ► Experimentally observed adsorption sites are revealed through density function theory calculations. ► Beyond monolayer coverage, molecular clusters are observed particularly near the step edges.