| AVS 54th International Symposium | |
| Surface Science | Thursday Sessions |
| Session SS1-ThA |
| Session: | Environmental Surfaces |
| Presenter: | F. Ostendorf, University of Osnabrueck, Germany |
| Authors: | F. Ostendorf, University of Osnabrueck, Germany C. Schmitz, University of Osnabrueck, Germany S. Hirth, University of Osnabrueck, Germany M. Reichling, University of Osnabrueck, Germany |
| Correspondent: | Click to Email |
Mineral surfaces play a key role in many reactions regarding mineral dissolution, precipitation and crystal growth. The most prominent of this type of surfaces in nano biology and material science is Muscovite mica. Air cleaved mica surfaces have been investigated by dynamic force microscopy operated in the non-contact mode (NC-AFM) under ultra-high vacuum (UHV) conditions with atomic resolution. In contrast to the common assumption that a simple degas under UHV conditions leads to a true atomically flat and clean surface, we demonstrate that the sample surface always exhibits a high density of small defects and clusters. In addition to these defective features we find flat and layered, hexagonally shaped islands exhibiting two different types of atomic scale patterns on different length scales: namely a rectangular pattern and a Moiré superstructure. In general one can consider that potassium ions of a mica surface - when cleaved in air - react with water and carbon dioxide. This composes potassium carbonate. By detailed measurements with atomic precision we clearly identify the unit cells of both patterns. The rectangular pattern is associated with the potassium carbonate unit cell. For growing potassium carbonate crystallites on mica surfaces the slight lattice mismatch needs to be compensated. This compensation is reflected by the observed Moiré superstructure. Finally we yield strong evidences that crystallites of potassium carbonate emerge due to the reaction with water and carbon dioxide and grow by Ostwald ripening on mica surfaces.