Allgemeines Physikalisches Kolloquium - WS 2013/14
| Ort: | 48149 Münster, Wilhelm-Klemm-Straße 10, IG 1, HS 2 |
| Zeit: | Donnerstag, 07.11.2013, 16 Uhr c.t. |
| Kolloquiums-Kaffe: ab 15:45 Uhr vor dem Hörsaal |
from oxide surface science to the discovery of new quasicrystals |
| Prof. Dr. Wolf Widdra, MPI für Mikrostrukturphysik, Universität Halle |
Recently the astonishing properties of new materials like the honeycomb-structured carbon monolayer of graphene or the topological insulators have widely opened the interests in purely 2-dimensional materials. These properties and the specific structure are often driven by the interface and can be well addressed by the broad range of experimental techniques which have been developed in surface science. In this talk I will present the structure formation at Perovskite oxide surfaces and ultrathin films on metal substrates. Growth, atomic structure, vibrational as well as ferroelectric properties at the vacuum interface have been investigated by electron diffraction, photoelectron spectroscopy and microscopy, vibrational spectroscopy, and scanning probe microscopy. The properties of ultrathin films differ from the properties of the respective bulk systems, either by the formation of structurally different oxide phases, by the strain from the oxide-metal misfit, or simply by the presence of the substrate.
Even more surprising, the interface interaction can lead to new 2D crystallographic phases and we demonstrate the formation of a 2-dimensional oxide quasicrystal with a perfect twelvefold diffraction pattern. The diffraction pattern results from a dodecagonal tiling pattern which is composed by squares and triangles as atomically resolved STM images show. Whereas any periodic order is clearly absent, a self-similarity of the structure is found.
Support by the German joint research network Sonderforschungsbereich 762 “Functionality of oxidic interfaces” of the Deutsche Forschungsgemeinschaft is gratefully acknowledged.
| Einladender: Prof. Dr. H. Zacharias |
| Im Auftrag der Hochschullehrer des Fachbereichs Physik |
| Prof. Dr. N.A. Stolwijk |