1. International Iberian Nanotechnology Laboratory (INL), 4715-330 Braga, Portugal
2. Nanoscale Physics Research Laboratory, School of Physics and Astronomy, University of Birmingham, Birmingham B15 2TT, United Kingdom
3. College of Engineering, Swansea University, Bay Campus, Fabian Way, Swansea SA1 8EN, United Kingdom
4. Ernst Ruska-Centre for Microscopy and Spectroscopy with Electrons and Peter Grünberg Institute, Forschungszentrum Jülich GmbH, 52425 Jülich, Germany
5. Tethis S.p.A., via Russoli 3, 20143 Milano, Italy