1. Leibniz-Institut für Kristallzüchtung, Max-Born-Str. 2, 12489 Berlin, Germany
2. Materials Research Institute and Department of Materials Science and Engineering, The Pennsylvania State University, University Park, Pennsylvania 16802, USA
3. Paul-Drude-Institut für Festkörperelektronik, Hausvogteiplatz 5-7, 10117 Berlin, Germany
4. Department of Computer Science and Engineering, University of South Florida, Tampa, Florida 33620, USA