1. Department of Materials Science and Engineering, Biomedical Engineering, Box 534, Uppsala University, SE- 75121Uppsala, Sweden
2. Department of Physics, Materials Physics, Box 530, Uppsala University, SE-75121Uppsala, Sweden
3. Department of Chemistry Ångström, Box 538, Uppsala University, SE-751 21Uppsala, Sweden
4. Department of Materials Science and Engineering, Nanotechnology and Functional Materials, Box 35, Uppsala University, SE- 75103Uppsala, Sweden