Swiss Nanoscience Institute 4056 Basel SwitzerlandBiozentrum University of Basel 4056 Basel SwitzerlandLaboratory for Micro and Nanotechnology Paul Scherrer Institut 5232 Villigen Switzerland;
Swiss Nanoscience Institute 4056 Basel SwitzerlandBiozentrum University of Basel 4056 Basel Switzerland;
Swiss Nanoscience Institute 4056 Basel SwitzerlandInstitute of Physics University of Freiburg D-79104 Freiburg Germany;
Swiss Nanoscience Institute 4056 Basel SwitzerlandLaboratory for Micro and Nanotechnology Paul Scherrer Institut 5232 Villigen Switzerland;