1. Department of Applied Physics, Chalmers University of Technology, SE-412 96 Göteborg,
Sweden
2. Department of Microtechnology
and Nanoscience, Chalmers University of Technology, SE-41296 Göteborg, Sweden
3. Department of Physics, Chemistry
and Biology, Linköping University, SE-581 83 Linköping,
Sweden
4. EaStCHEM, School
of Chemistry, University of Edinburgh,
Edinburgh EH9 3JJ, Scotland
5. Division of Quantum Phases and
Devices, Department of Physics, Konkuk University, Seoul 143-701, Korea