1. Department of Mathematics and Physics, School of Computing, Engineering and Mathematical Sciences, La Trobe University, Victoria 3086, Australia
2. Fraunhofer Institute for Integrated Systems and Device Technology IISB, Schottkystrasse 10, D-91058 Erlangen, Germany
3. nano analytik GmbH, Ehrenbergstraße 3, 98693 Ilmenau, Germany
4. Technische Universität Ilmenau, Nanoscale Systems Group, Gustav-Kirchhoff-Straße 1, 98693 Ilmenau, Germany