1. Institute for Integrative Nanosciences; IFW Dresden; Helmholtzstraße 20 01069 Dresden Germany
2. Department of Applied Physics; The Hong Kong Polytechnic University; Kowloon Hong Kong P. R. China
3. The Hong Kong Polytechnic University Shenzhen Research Institute; 518057 Shenzhen P. R. China
4. Institute für Festkörperphysik; Leibniz Universität Hannover; 30167 Hannover Germany
5. Material Systems for Nanoelectronics; Technische Universität Chemnitz; 09107 Chemnitz Germany