1. Advanced Research Centre for Nanolithography (ARCNL), Science Park 106, 1098 XG Amsterdam, The Netherlands
2. Van der Waals-Zeeman Institute, University of Amsterdam, Science Park 904, 1098 XH Amsterdam, The Netherlands
3. Department of Physics and Astronomy, Vrije Universiteit, De Boelelaan 1081, 1081 HV Amsterdam, The Netherlands