Broken symmetry induced band splitting in the Ag2Ge surface alloy on Ag(111)
2014 (English)In: Physical Review B. Condensed Matter and Materials Physics, ISSN 1098-0121, E-ISSN 1550-235X, Vol. 89, no 12, 125410-1-125410-6 p.Article in journal (Refereed) Published
We report a study of the atomic and electronic structures of the ordered Ag2Ge surface alloy containing ⅓ monolayer of Ge. Low-energy electron diffraction (LEED), scanning tunneling microscopy (STM), and angle-resolved photoelectron spectroscopy (ARPES) data reveal a symmetry breaking of the expected √3 × √3 periodicity, which is established for other Ag2M alloys (M = Bi, Sb, Pb, and Sn). The deviation from a simple √3 × √3 structure manifests itself as a splitting of diffraction spots in LEED, as a striped structure with a 6× periodicity including a distortion of the local hexagonal structure in STM, and as a complex surface band structure in ARPES that is quite different from those of the other Ag2M alloys. These results are interesting in view of the differences in the atomic and electronic structures exhibited by different group IV elements interacting with Ag(111). Pb and Sn form √3 × √3 surface alloys on Ag(111), of which Ag2Pb shows a surface band structure with a clear spin-orbit split. Si and C form silicene and graphene structures, respectively, with linear band dispersions and the formation of Dirac cones as reported for graphene. The finding that Ag2Ge deviates from the ideal (√3 × √3) Ag2Sn and Ag2Pb surface alloys makes Ge an interesting “link” between the heavy group IV elements (Sn, Pb) and the light group IV elements (Si, C).
Place, publisher, year, edition, pages
American Physical Society , 2014. Vol. 89, no 12, 125410-1-125410-6 p.
IdentifiersURN: urn:nbn:se:liu:diva-105259DOI: 10.1103/PhysRevB.89.125410ISI: 000332460600003OAI: oai:DiVA.org:liu-105259DiVA: diva2:705047