Affiliation: | a Department of Physical Sciences, University of Helsinki, P.O. Box 64, 00014 HU, Finland b Department of Materials Chemistry, Tampere University of Technology, P.O. Box 541, 33101 Tampere, Finland c Institut für Festkörperforschung, Forschungszentrum Jülich GmbH, D-52425 Jülich, Germany d VTT Biotechnology, P.O. Box 1500, 02044 VTT, Finland |