1. Institute of Materials and Surface Engineering Faculty of Natural Sciences and Technology Riga Technical University Riga LV‐1048 Latvia
2. School of Science RMIT University Melbourne 3000 Australia
3. Institute of Solid State Physics University of Latvia Riga LV‐1063 Latvia
4. Institute of Biomaterials and Bioengineering Faculty of Natural Sciences and Technology Riga Technical University Riga LV‐1048 Latvia
5. Institute of Technical Physics Faculty of Natural Sciences and Technology Riga Technical University Riga LV‐1048 Latvia