|Prof. Ernst Bauer
|Department of Physics, Arizona State University
|Nanoscale Patterns on Polar Oxide Surfaces
|Polar ionic surfaces with bulk termination are inherently unstable because of their diverging electrostatic surface energy. Nevertheless, they are frequently observed in nature, mainly because of charge neutralization by adsorbates, but occur also under atomically clean conditions. Several mechanisms have been invoked to explain the stability of atomically clean polar surfaces, but the frequently observed periodic nanoscale pattern formation has not yet been explained. Here we propose that long-range interactions between alternating electropositive and electronegative regions of different surface terminations minimize the electrostatic energy of the surface and thus stabilize the nanoscale pattern. This is illustrated with the polar Fe2O3(0001) and Fe3O4(111) surfaces, which are important in heterogeneous catalysis, by combining scanning tunneling microscopy and spectroscopy results with results from density functional theory-based calculations and dipole－dipole interaction models.
|グリーンフォトニクス分野 三澤 弘明（内線9358）