1. Surface Science Group, Faculty of Engineering and Natural Sciences, Tampere University, P.O. Box 692, FI 33014 Tampere, Finland
2. Tampere Microscopy Center, Faculty of Engineering and Natural Sciences, Tampere University, P.O.
Box 692, FI 33014 Tampere, Finland
3. Faculty of Engineering and Natural Sciences, Tampere University, P.O. Box 692, FI 33014 Tampere, Finland