1. Electrical and Computer Engineering Department, Duke University, Durham, North Carolina 27705, United States
2. Institute of Inorganic Methodologies and of Plasmas, IMIP-CNR, via Orabona 4, 70126 Bari, Italy
3. Centre for Microscopy, Characterisation and Analysis, The University of Western Australia, Crawley, Western Australia 6009, Australia
4. Electron Microscope Unit, Bio21 Institute, University of Melbourne, Melbourne, Victoria 3010, Australia
5. Profactor GmbH, Im Stadtgut A2, 4407 Steyr-Gleink, Austria