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O: Fachverband Oberflächenphysik
O 107: Semiconductor Surfaces (joint session O/HL)
O 107.7: Vortrag
Donnerstag, 19. März 2020, 16:45–17:00, REC C 213
Doping-induced metal-insulator transition in Au atomic wires — •Zamin Mamiyev1, Simone Sanna2, Christoph Tegenkamp1, and Herbert Pfnür1 — 1Appelstrasse 2 Institut für Festkörperphysik, Leibniz Universität Hannover, Hannover, Germany — 2Institut für Theoretische Physik, Justus-Liebig- Universität Gießen
Close coupling between structural and electronic parameters has been demonstrated in the past for arrays of quasi one-dimensional Au chains on Si surfaces. Here we employ plasmon spectroscopy and LEED to study electronic and structural modifications as a result of surplus Au concentrations, x, starting at 0.48 ML on Si(553) and at 0.65 ML on Si(111). For the Si(111)-Au surface an abrupt metal-insulator transition (MIT) was observed by adding more than 0.05 ML Au. In contrast, the Si(553)-Au surface shows a rather gradual decrease of plasmon frequency up to x= 0.1 ML. Moreover, self-doping with Au on Si(553)-Au improves the chain quality up to x=0.03 ML, resulting also in an increase of plasmon intensity. Further addition of Au at room temperature leads to a vanishing plasmon frequency, coupled with the disappearance of the ×2 periodicity. By annealing the doped samples at 630∘C the Au atoms form small clusters with (√3×√3)R30∘ symmetry, while the metallicity of the Au chains is fully recovered, but the structural imperfections in the chains as well. The appearance of √3-order indicates local restructuring into larger terraces and their spatial separation from the Au-chains. This proves that not only the amount of dopant but also its distribution is important for reversible MIT on such surfaces. These findings were corroborated by DFT calculations.