1. Center for Nano Science and Technology @PoliMi, Istituto Italiano di Tecnologia, 20133 Milan, Italy
2. The Molecular Foundry, Lawrence Berkeley National Laboratory, Berkeley, California 94720, United States
3. Micro and Nanostructured Materials Lab, Department of Energy, Politecnico di Milano, 20133 Milan, Italy
4. Materials Characterization Facility, Istituto Italiano di Tecnologia, 16163 Genova, Italy