Sub-Monolayer Annealed CuPc on Cu(111): Defect Hindered Dynamic Clusters*

Annealed sub-monolayer copper phthalocyanine on Cu(111) was studied with room temperature scanning tunneling microscopy (STM) and density functional theory (DFT). At coverages of 0.25 ML we observed that annealing produces a disordered cluster network of CuPc that attach together by forming C-C bonds across isoindole lobes. At lower coverages we find that smaller CuPc clusters (less than ~20 CuPc in size) are mobile on the Cu(111) surface. This dynamic motion was tracked by repeated STM image scans. Subsequent deposition of CuPc (without annealing) produced a Cu(111) surface covered with highly mobile single CuPc molecules and less mobile CuPc clusters. This enabled resolution of surface defects that were found to immobilize the CuPc clusters through a defect pinning mechanism.