Adsorption and ordering of PTCDA on various reconstruction surfaces of In/Si(1Â 1Â 1)

The adsorption and ordering of 3,4,9,10-perylene-tetracarboxylic-dianhydride (PTCDA) molecules on various reconstruction surfaces of the In/Si(111) at room temperature were examined by using scanning tunneling microscope. On the semiconducting √31x√31 surface, the PTCDA molecules adsorbed randomly and were isolated without ordering, whereas the molecules adsorbed on the metallic 4 × 1 and 'striped' surfaces were mobile and self-assembled to form regular structures. The assembled structures were governed by the dimensionality of the substrate structures. On the quasi-one-dimensional 4 × 1 surface, the PTCDA molecules with the same orientations were confined between the In chains to form molecular wires. On the other hand, the molecules formed a herringbone arrangement on the two-dimensional 'striped' surface via hydrogen bonding between the molecules. The different molecular arrangements on the two metallic surfaces reflect the relative predominance of the molecule-substrate interactions on the 4 × 1 surface and of the molecule-molecule interactions on the 'striped' surface.