Kondo effect in single cobalt phthalocyanine molecules adsorbed on Au(111) monoatomic steps

The Kondo effect in single dehydrogenated cobalt phthalocyanine (CoPc) molecules adsorbed on Au(111) monoatomic steps was studied with a low temperature scanning tunneling microscope. The CoPc molecules adsorbed on Au(111) monoatomic steps show two typical configurations, which can be dehydrogenated to reveal Kondo effect. Moreover, the Kondo temperatures (T-K) measured for different molecules vary in a large range from similar to 150 to similar to 550 K, increasing monotonically with decreasing Co-Au distance. A simple model consisting of a single Co 3d(z)(2) orbital and a Au 6s orbital is considered and gives a qualitative explanation to the dependence. The large variation of T-K is attributed to the variation of the interaction between the magnetic-active cobalt ion and the Au substrate resulted from different Co-Au distances. (C) 2008 American Institute of Physics.