1. Division Biophotonics, Federal Institute for Materials Research and Testing (BAM), 12489Berlin, Germany
2. PhysNano Department, ITMO University, 197101Saint Petersburg, Russia
3. AG Strukturforschung/Elektronenmikroskopie Institut für Physik, Humboldt-Universität zu Berlin, 12489Berlin, Germany
4. Division Surface Analysis and Interfacial Chemistry, Federal Institute for Materials Research and Testing (BAM), 12203Berlin, Germany