Differences in adsorption of FePc on coinage metal surfaces

A study of the electronic and structural properties of iron phthalocyanine (FePc) molecule adsorbed on coinage metal surfaces Cu (100) and Cu (110) has been conducted by means of density functional theory calculations. The strength of the molecule-substrate interactions is interpreted in terms of the lateral adsorption geometry and the site specific electronic structure of the molecule. In the case of FePc on (100)-oriented copper surface, the benzopyrrole leg is found to be oriented at an angle of 9° or 3° from the 01-1 substrate direction. Further, an upward bend in the molecular plane ranging from 7° to 10° is also observed; giving an almost buckled shape to the molecule. However, in the case of FePc on Cu (110), neither a bend nor a sizable rotation is observed. From general knowledge of the principals of structural and electronic properties, it is concluded that FePc-Cu (100) interaction is relatively stronger than FePc-Cu (110) interaction, which is further evidenced by the charge transfer, work function changes, changes in the shape of the adsorbed molecular orbitals, and the orbital shifts. Furthermore, a density of states analysis shows that valence band level shift is surface- and site-dependent.