Novel mechanism for molecular self-assembly on metal substrates: unidirectional rows of pentacene on Cu(110) produced by a substrate-mediated repulsion.

The formation of one-dimensional, unidirectional nanoscopic molecular structures by self-assembly on metal substrates with a long range ordering up to several hundred nanometers has been achieved by a novel mechanism, an oscillatory modulation of the adsorption energy due to charge-density waves related to a surface state. For the case of pentacene (C22H14) adsorbed on Cu(110), annealing at 400 K produces a regular pattern of molecular wires one molecule wide (15.6 A) and a wire-to-wire distance of 28+/-2 A. Results obtained for similar compounds suggest that the underlying mechanism is rather general and can be applied also for other linear aromatic molecules.