Interaction of metallophthalocyanines (MPc, M=Co, Ni) on Au(001):: Ultraviolet photoemission spectroscopy and low energy electron diffraction study

Thin films of metallophthalocyanine (MPc,M=Co,Ni) evaporated onto a "5x20" reconstructed Au(001) substrate at room temperature have been investigated by employing low energy electron diffraction (LEED) and ultraviolet photoelectron spectroscopy (UPS). The LEED images from NiPc thin films show that the overlayers are highly ordered with a square unit cell of 12.8x12.8 A(2) aligned along the < 110 > and < 1 (1) over bar0 > axes of the Au(001) substrate. For CoPc, the LEED pattern reveals the superposition of multiple rotationally equivalent domains of a 12.9x12.9 A(2) square lattice which are rotated by 16 degrees with respect to each other. The contrast between NiPc and CoPc on Au(001) is further demonstrated in the interfacial electronic structure. UPS studies of the interfacial layers of NiPc deposited on the hexagonally reconstructed gold substrate indicate that NiPc physisorbs on the gold surface as evidenced by a uniform molecular orbital (MO) shift. The CoPc MO's, on the other hand, indicates a charge transfer at the interface, evidenced by the 13a(1g) MO interacting with the Au surface. (c) 2006 American Institute of Physics.