STM and STS investigation of ultrathin tin phthalocyanine layers adsorbed on HOPG(0001) and Au(111)

The initial adsorption of tin phthalocyanine (SnPc) on graphite and gold su rfaces was studied by low-temperature UHV-STM. At submonolayer coverages on highly oriented pyrolytic graphite (HOPG), SnPc forms substrate-defined mo lecular chains, while SnPc monolayers reveal dense packed structures with t he molecules symmetry. A comparitive study with CuPc on HOPG reveals simila r chains in the submonolayer regime. No chains were found upon SnPc adsorpt ion onto Au(1 1 1). At ordered SnPc/HOPG films with thickness around one mo nolayer, local I(V) curves were collected with high reproducibility. Their wide energy gap shows the semiconductive properties of the SnPc monolayers. A strongly increased differential conductivity was observed at distinct en ergy values. (C) 2001 Elsevier Science B.V. All rights reserved.