Dresden 2011 – wissenschaftliches Programm
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O: Fachverband Oberflächenphysik
O 69: Electronic structure I
O 69.1: Vortrag
Donnerstag, 17. März 2011, 11:15–11:30, WIL C107
Structural/electronic interplay in tunable dislocation networks — •Frederik Schiller1, Zakaria Abd-el-Fattah1, Manfred Matena2, Javier Cordon3, and Enrique Ortega1,2,3 — 1Centro de Fisica de Materiales (CFM-CSIC), Materials Physics Center (MPC), San Sebastian, Spain — 2Donostia International Physics Center, San Sebastian, Spain — 3Dpto. Fisica Aplicada, Universidad del Pais Vasco, San Sebastian, Spain
Moiré and strain dislocation networks arise when a monolayer or two of one material grows on a substrate with the same crystal symmetry but different atomic lattice constant. Beyond their use as growth templates, such metallic superlattices may be used as model two-dimensional metallic superstructures at which surface states scatter, thereby leading to two-dimensional superlattice band folding and gap opening. The Ag monolayer on Cu(111) system, with its characteristic free-electron-like surface state, is a prototype scenario. At low temperature, it forms a perfect coincidence lattice (Moiré), which transforms into a hexagonal array of triangular dislocations by annealing above 300 K. Such structural transition is accompanied by a deep surface state transformation, i.e., from a parabolic band in the Moiré structure to a superlattice-folded and gapped two-dimensional band structure in the dislocation network. The latter features a full 25 meV gap that can be brought below the Fermi level by lowering the temperature or by gold doping, thereby making the noble metal surface effectively semiconducting.