Properties and origin of one-dimensional Au nanostructures on tungsten surface carbides

We introduce a universal template for one-dimensional self-organization. The tungsten surface carbide W(110)/C-R(15 x 3) displays a large-scale reconstruction with interesting properties. We recently showed that this structure which is rotated by 14 circle relative to W is able to order various atomic species ranging from C60 superclusters which show ''magic'' numbers to Au films which become patterned in a way that they in turn serve as templates for needle-shaped Ni clusters. The Au reconstruction is uniaxial with corresponding one-dimensional E(k) dispersion. We demonstrate the origin of the self-organization of Au comparing (15 x 12) and (15 x 3) templates by STM and LEED. Two principally different mechanisms are identified: At room temperature, regular Au clusters develop which are 1 monolayer high when grown on the (15 x 12) structure and 2 monolayers high on (15 x 3) but always aligned along the physical potential of the carbide nanomesh, i. e., off by 14 circle. Annealing rearranges the Au adatoms towards a nanowire-like reconstruction which has rotated back to the [001] of W. The chemical driving force for this is revealed in detail by photoemission spectra from the valence band and the W4f core level