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O: Oberflächenphysik

O 40: Oxides and insulators

O 40.11: Vortrag

Donnerstag, 30. März 2006, 17:30–17:45, WIL A317

Local differential conductance of thin CoO films on Ag(001) at low temperatures — •Stephan Grosser, Christian Hagendorf, and Wolf Widdra — Martin-Luther-Universität Halle-Wittenberg, FB Physik, D-06120 Halle(Saale)

Scanning tunneling microscopy (STM) and scanning tunneling spectroscopy (STS) have been applied to study simultaneously the local electronic and geometric structure of thin CoO films on Ag(001). CoO has been grown by reactive deposition of Co in an O₂ atmosphere. Growth at 480 K substrate temperature leads to precursor or unordered phases and subsequent annealing to ordered CoO(001) films.
dI/dV spectra for structurally well-characterized different precursor phases, CoO bilayer and layers up to 5 ML show distinct differences. The region of the unoccupied states up to 5 eV is dominated by the local density of states within the oxide film. Especially for 2 ML islands and thicker films, a strong and well-resolved unoccupied Co d-state at about 2.3 eV is found. For higher bias voltages between 5 and 10 V the spectra exhibit strong field emission resonances which are characteristically modified by the different oxide structures as compared to the bare metal substrate. Topographic and simultaneous measured spectroscopic maps reveal details of the lateral electronically homogeneity and defect distribution down to atomic resolution. The results will be compared with spectra for Ag(001) and first results of NiO on Ag(001).