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

► 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.