Scanning tunneling microscopy and photoelectron spectroscopy investigation of the sexithiophene:C60 donor-acceptor nanostructure formation on graphite

The organic donor-acceptor nanostructure formation processes of C-60 and alpha-sexithiophene (6T) on graphite are monitored by in situ low-temperature scanning tunneling microscopy and synchrotron-based photoelectron spectroscopy experiments. It is found that the intermolecular interaction between C-60 and 6T plays a key role in the formation of organic nanostructures on graphite. Room temperature deposition of C-60 on the 6T monolayer on the weakly interacting graphite substrate results in the coexistence of three energetically stable structural motifs with a well-defined supramolecular arrangement, including C-60 zigzag filament, C-60 hexagon and C-60-pair filament, and hence the formation of C-60:6T molecular glass on graphite. Our results show that only the thermally stable C-60 zigzag filaments can develop into a long-range ordered two-dimensional C-60 zigzag chain array by annealing the system at 350 K. (C) 2011 American Institute of Physics. [doi: 10.1063/1.3573779]