Berlin 2008 – wissenschaftliches Programm

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O: Fachverband Oberflächenphysik

O 7: Symposium: Atomic Wires at Surfaces I
(Invited Speakers: Franz Himpsel, Hanno Weitering, Han Woong Yeom)

O 7.2: Vortrag

Montag, 25. Februar 2008, 11:45–12:00, HE 101

Properties and origin of one-dimensional Au nanostructures on tungsten surface carbides — •Andrei Varykhalov, Oliver Rader, and Wolfgang Gudat — BESSY Berlin

We introduce a universal template for one-dimensional self-organization. The tungsten surface carbide W(110)/C-R(15×3) displays a large-scale reconstruction with interesting properties [1,2]. We recently showed that this structure which is rotated by 14^∘ 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 [3]. The Au reconstruction is uniaxial with corresponding one-dimensional E(k) dispersion [3]. We will demonstrate the origin of the self-organization of Au comparing (15×12) and (15×3) 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 (15×12) structure and 2 monolayers high on (15×3) but always aligned along the physical potential of the carbide nanomesh, i. e., off by 14^∘. 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.

[1] M. Bode et al., Surf. Sci. 344, 185 (1995). [2] A. Varykhalov et al., Phys. Rev. B 72, 115440 (2005). [3] A. Varykhalov et al., Phys. Rev. B 73, 241404(R) (2006); 74, 95420 (2006); 72, 241404(R) (2005).