Berlin 2008 – wissenschaftliches Programm
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O: Fachverband Oberflächenphysik
O 32: Oxides and Insulators: Clean Surfaces
O 32.10: Vortrag
Dienstag, 26. Februar 2008, 15:15–15:30, MA 042
Metal-insulator transition on the V2O5(001) surface: Theory and experiment — •Maria Veronica Ganduglia-Pirovano1, Remy Fortrie1, Joachim Sauer1, Ralf-Peter Blum2, Horst Niehus2, Carsten Hucho3, Shamil Shaikhutdinov4, and Hans-Joachim Freund4 — 1Inst. für Chemie, HU-Berlin — 2Inst. für Physik, HU-Berlin — 3Paul-Drude-Institut Berlin — 4FHI Berlin
Several vanadium oxides undergo a metal-to-insulator transition (MIT) in the bulk, e.g., V2O3 at ∼150 K,
VO2 at 340 K, whereas V2O5 is a semiconductor. Experimental evidence for a thermally induced surface insulator-metal transition (MIT) at the V2O5(001) surface at 350-400 K is presented.
This surface exposes vanadyl (V=O) double rows along the [010] direction. Using density functional theory (DFT) in combination with statistical thermodynamics,
the facile reduction along the rows was predicted.[1] The experimentally observed MIT transition expands preferentially in the direction of these rows. We then used the
Monte Carlo method to simulate the
reduced V2O5(001) surface at a given temperature and defect concentration. We typically find
areas with a random distribution of isolated defects and others with up to 5 sites forming [010] oriented trenches. Using calculated band gaps
for reduced V2O5 structures as obtained
with DFT+U, we construct band gaps maps which agree with those derived from scanning tunneling spectroscopy data; only the areas
with defective rows are metallic.
[1] M. V.
Ganduglia-Pirovano and J. Sauer, PRB 70, 045422 (2004).
[2] R.-P. Blum, H. Niehus, C. Hucho et al.,
PRL. in press.