Morphology and structure of copper-phthalocyanine and iron-phthalocyanine thin films on Ag(111)

Copper-phthalocyanine and iron-phthalocyanine have been in situ deposited onto Ag(111) surface at room temperature by vacuum sublimation. Thin heteroepitaxial films formed thereof have been investigated using scanning tunneling microscopy. When annealed up to $\sim $ 500\r{ }K, both molecules form well-ordered square lattices on the hexagonal substrate lattice but result in different molecular orientations within the surface unit cell. For CuPc, benzo units of the molecules are rotated by approximately 30\r{ } with respect to the surface lattice vectors forming a high-density packing whereas for FePc the benzo units are rotated by about 45\r{ }. Consequently, the square lattice constant for CuPc measured at $\sim $14 {\AA} is significantly smaller than that of $\sim $16 {\AA} for FePc. Annealing to $\sim $700\r{ }K results desorption of as much as 70{\%} of surface monolayer of phthalocyanine molecules. The aggregates are observed in dendrite-like form, and further discussion of temperature effects on CuPc and FePc thin films will be presented.