Publications in Scientific Journals:
C. Klein, G. Kresse, S. Surnev, F.P. Netzer, M. Schmid, P. Varga:
"Vanadium surface oxides on Pd(111): A structural analysis";
Physical Review B,
Scanning tunneling microscopy (STM) studies of vanadium oxides grown on Pd(111) show interesting structures especially in the low coverage region.
Evaporation of V in an oxygen background at elevated sample temperature (250 °C) results in the formation of a non-periodic honeycomb-like structure
growing from the steps, which starts to transform into an ordered phase at a vanadium coverage of approx. 0.2 monolayers (ML). At 0.31 ML the entire
surface is covered by this well-ordered open (4x4) structure. Annealing this structure in H2 atmosphere transforms the phase into a V2O3 surface oxide
with (2x2) periodicity, whose optimal coverage is reached at 0.5~ML vanadium. Models for both ordered structures have been suggested before on the basis
of ab initio density functional theory (DFT) calculations and molecular dynamics simulations and these models are now unambiguously confirmed by
quantitative low energy electron diffraction (LEED) analyses. In the (4x4) phase, the V atoms are surrounded by four oxygen atoms in an unusual tetrahedral
coordination leading to a V5O14 stoichiometry. This tetrahedral coordination allows the oxide to adopt open loosely packed two-dimensional (2D) and 1D
structures, which are stabilized by the surface-oxide interface energy. Furthermore, it is shown that state of the art DFT calculations can indeed predict
complex structures exactly as well as that modern quantitative LEED is capable of dealing with very large unit cells.
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Created from the Publication Database of the Vienna University of Technology.