Dresden 2003 – wissenschaftliches Programm

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O: Oberflächenphysik

O 12: Postersitzung (Struktur und Dynamik reiner Oberfl
ächen, Grenzfl
äche fest-flüssig, Nanostrukturen, Teilchen und Cluster, Halbleiteroberfl
ächen und Grenzfl
ächen, Zeitaufgelöste Spektroskopie, Rastersondentechniken, Methodisches)

O 12.31: Poster

Montag, 24. März 2003, 18:00–21:00, P1

The adsorption of Barium on Si(100) studied with LEED and XRD — •Nicole Jeutter, Alexander Hirnet, and Wolfgang Moritz — Department of Earth and Environmental Sciences, Section Crystallography, University of Munich, Germany

The adsorption of Ba on Si(100) has been studied because it is supposed to from the interface in epitaxial Sr/BaTiO₃- and high T_c oxide-layers on Si(100). Ba shows basically three different adsorption structures at submonolayer coverages. From 1/6 up to 1/3 ML a (2 × 3) structure occurs, between 1/3 and 1/2 ML a c(2 × 6) structure is coexisting with the (2 × 3) structure. Above 1/2 ML on a (2 × 1) structure occurs. None of these structure has been umambiguously solved until now. Several models have been proposed mainly assuming Ba in the brigde or valley brigde position while the Si-dimer of the clean surface remains. First results of our LEED and XRD measurements show that none of the proposed models is consistent with the data. XRD measurements during annealing show that the (2 × 3) structure exhibits an order-disorder phase transition between 950 and 1000 K. After an oxygen exposition up to 1000 L at 1000 K a new phase, presumedly a silicide phase, with a lattice constant of 0.217 nm and the orientation of the unit mesh parallel to the [100] and [010] direction of the substrate cell has been observed.