Regensburg 2010 – scientific programme
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O: Fachverband Oberflächenphysik
O 23: Nanostructures at surfaces: Dots, particles, clusters
O 23.3: Talk
Tuesday, March 23, 2010, 11:00–11:15, H33
Gundlach oscillations and Coulomb blockade of Co nano-islands on MgO/Mo(100) — •Marco Pratzer, Christian Pauly, Martin Grob, and Markus Morgenstern — II. Physikalisches Institut B and JARA-FIT, Otto-Blumenthal-Straße, RWTH Aachen, 52074 Aachen
We studied the electronic properties of ultra thin MgO films (thickness 2 ML to 11 ML) on Mo(100) by scanning tunneling microscopy and spectroscopy at room temperature. Preparation of MgO has been done by molecular beam epitaxy of magnesium in O2 partial pressure of p=10−7 mbar. The work function differences of the MgO film are mapped by field emission resonance states (Gundlach oscillations) by dz/dU-spectroscopy. We found parts of islands with significantly reduced workfunction (Δ Φ=0.6 eV), which are tentatively assigned to charged defects within the MgO film. On top of the MgO films we prepared Co nano-islands with an area of about A=4 nm2 by molecular beam epitaxy. Due to the small capacity of the Co islands we observed Coulomb staircases at room temperature, respectively peaks in dI/dU-spectroscopy. Good agreement with orthodox theory is achieved showing variations of Q0 for islands at different positions.