1. IMEC, Kapeldreef 75, Leuven, Belgium
2. Solid State Physics, Ghent University, 9000 Ghent, Belgium
3. Laboratory of Solid State Physics and Magnetism, KU Leuven, 3001 Leuven, Belgium
4. Instituut voor Kern- en Stralingsfysica, KU Leuven, 3001 Leuven, Belgium
5. Graduate School of Engineering, Osaka University, 565-0871 Osaka, Japan
6. IMEC, Kapeldreef 75, 3001 Leuven, Belgium