1. VTT Technical Research Centre of Finland,
P.O. Box 1000, FI-02044 VTT, Espoo, Finland
2. Department
of Physics, University of Jyväskylä, P.O. Box 35, FI-40014, Jyvaskyla, Finland
3. Department
of Chemistry, School of Chemical Technology, Aalto University, P.O. Box 16100 FI-00076 Espoo, Finland
4. Department
of Solid State Sciences, Ghent University, Krijgslaan 281/S1, Gent B-9000, Belgium