1. Institute
for Integrative Nanosciences, Leibniz Institute for Solid State and Materials Research (IFW Dresden), Helmholtzstrasse 20, Dresden 01069, Germany
2. Material
Systems for Nanoelectronics, Technische Universität Chemnitz, Reichenhainer Strasse 70, Chemnitz 09107, Germany
3. College
of Material Science and Technology, Nanjing University of Aeronautics and Astronautics, Yudao Street 29, Nanjing 210016, P. R. China
4. Institut
für Festkörperphysik, Leibniz Universität Hannover, Appelstrasse 2, Hannover 30167, Germany