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Surface topography dependent desorption of alkali halides
1Institute of Physics, Jagiellonian University, Reymonta 4, 30-059 Krakow, Poland.
Physical Review Letters
|September 8, 2000
Summary
Electron-stimulated desorption of potassium bromide (KBr) surfaces reveals oscillatory patterns in K and Br desorption, linked to surface topography changes during layer-by-layer removal. This suggests terrace edges trap excited F centers, influencing crystal deexcitation pathways.
Area of Science:
- Surface Science
- Materials Science
- Solid State Physics
Background:
- Electron-stimulated desorption (ESD) is crucial for understanding material modification under electron irradiation.
- Potassium bromide (KBr) is a model ionic crystal with applications in optics and electronics.
- Surface topography significantly influences desorption dynamics and material properties.
Purpose of the Study:
- To investigate the electron-stimulated desorption (ESD) of the (100)KBr surface.
- To correlate desorption behavior with surface topography changes.
- To elucidate the role of surface features in the deexcitation mechanisms of excited states.
Main Methods:
- Noncontact atomic force microscopy (AFM) for high-resolution surface topography imaging.
- Mass spectroscopy for identifying and quantifying desorbed species (K and Br).
- Controlled electron irradiation in vacuum to induce desorption.
Main Results:
- Both K and Br desorption components exhibited an oscillatory dependence on electron dose.
- The amplitude of these oscillations decayed gradually with increasing electron dose.
- Surface topography was found to vary periodically, consistent with layer-by-layer desorption.
Conclusions:
- Surface terrace edges act as preferential trapping sites for excited F centers.
- The oscillating density of terrace edges modulates F center recombination and reflection rates.
- This modulation influences the balance between surface and bulk deexcitation pathways in KBr.