SCANNING TUNNELING MICROGRAPHS OF ORDERED LAYERS OF 2 THIOPHENE-ALKYLPYRROLE OLIGOMERS ON GRAPHITE

Scanning tunneling micrographs of two linear oligomers with six and se ven units of thiophene (S) and N-dodecylpyrrole (P-12) arranged as SP1 2SSP12S (molecule 1) and SP12SP12SP12S (molecule 2) dissolved in pheny loctane, and imaged on a highly oriented pyrolytic graphite with a Pt/ Ir tip, show ordered rows (lines) of oligomers. Molecule 1 has a singl e packing structure, an interline repeat distance of 19+/-0.5 Angstrom perpendicular to the bright lines (aromatic rings) and dark regions ( dodecyl tails), and an intraline distance of 8+/-0.3 Angstrom. Molecul e 2 shows three domains with subtly different molecular ordering, with repeat distances of 23+/-0.5 Angstrom (interline) and 18+/-0.5 Angstr om (intraline). For both molecules the aromatic rings may lie almost i n the graphite plane.