Scanning tunnelling microscopy (STM), which yields lateral and vertical resolution in the sub-nm range, was applied to thin films of stoichiometric, oxygen-sensitive Ga2O3. In a next step a combined STM and Auger electron spectroscopy study was performed for ultra-thin platinum metallizations of these Ga2O3 ceramic carriers. The drastically enhanced activity and its degradation at temperatures around 1000 K of this real supported catalyst with respect to CO oxidation rates is demonstrated by means of a quadrupole mass spectrometer in varying O2/CO atmospheres. For the first time STM images and images of the local barrier height of these ultra-thin Pt layers are shown before and after degradation of the catalytic activity. Special care has been taken to prepare tunnelling tips of extremely low curvature radii and of sufficiently high mechanical stability to enable realistic imaging of these rough surfaces to be performed. General guidelines for tip-shape preparation result from a finite-element simulation of d.c. etched tungsten tips.
ASJC Scopus subject areas
- Electronic, Optical and Magnetic Materials
- Condensed Matter Physics
- Surfaces, Coatings and Films
- Metals and Alloys
- Electrical and Electronic Engineering
- Materials Chemistry