Regensburg 2002 – wissenschaftliches Programm

Bereiche | Tage | Auswahl | Suche | Downloads | Hilfe

O: Oberflächenphysik

O 17: Oxide und Isolatoren (I)

O 17.2: Vortrag

Dienstag, 12. März 2002, 11:30–11:45, H43

Structural analysis of the BaTiO₃(111)(√3 × √3)R30^∘ surface using tensor LEED — •J. Wang, Ch. Ammer, Ch. Hagendorf, H. Neddermeyer, and K.-M. Schindler — Martin-Luther-Universität Halle-Wittenberg, FB Physik, D-06099 Halle

The ferroelectric and dielectric properties of barium titanate (BaTiO₃) make it a prime candidate for memory technology. From the various reconstructions of the (111) surface, we selected the (√3 × √3)R30^∘ reconstruction because of its stability. In order to remove contaminants and create the reconstruction the sample was annealed in vacuum at 1470 K. The reduction of the surface was monitored with XPS through the appearance of Ti³⁺ shoulders in the Ti 2p photoemission lines. The surface structure was investigated by means of tensor LEED. Structural models with Ba-O and Ti terminations of the surface as well as oxygen vacancies were selected on the basis of STM images. A data set of 8 nondegenerate beams and a total energy range of 800 eV was used to automatically optimize the agreement between theoretical and experimental LEED I(V) curves. Best agreement (r-factor: 0.36) was achieved with a BaO-terminated surface and the presence of oxygen vacancies. In addition, strong vertical relaxations have been found in the two topmost BaO-Ti double layers. The structural results will be discussed in relation to other theoretical and experimental investigations.