1. Faculty of PhysicsSt. Petersburg State University Ulyanovskaya 1 St. Petersburg 198504 Russia
2. IRC Nanotechnology, Research ParkSt. Petersburg State University Ulyanovskaya 1 St. Petersburg 198504 Russia
3. Department of Simulation & CharacterizationLeibniz-Institut für Kristallzüchtung Max-Born-Straße 2 12489 Berlin Germany