Segregation of molecular overlayers with different structures on a metal surface

Segregation of molecular overlayers having different structures depending on the molecular structure was observed by using scanning tunneling microscope in ultra-high vacuum at 77.5 K. Two kinds of molecules, chloro[tri-tert-butyl-subphthalocyaninato]boron(III) (TBSubPc) and phenyl[tri-tert-butyl-subphthalocyaninato]boron(III) (phenyl-TBSubPc), were successively co-deposited on an Au (111) surface. Two different overlayer structures were clearly identified: a honeycomb lattice consisting of phenyl-TBSubPc molecules and a quasi-hexagonal lattice consisting of TBSubPc molecules. This behavior suggests that the molecules can interact strongly with the same molecules to form their own overlayer structure. The difference in the central part of the molecular structures affects the intermolecular interaction resulting in the segregation of molecular overlayers.