1. Department of Materials Science and Metallurgy, University of Cambridge, Cambridge CB3 0FS, United Kingdom
2. Department of Electrical and Electronic Engineering, The University of Hong Kong, Pokfulam Road, Hong Kong
3. Experimental Techniques Centre, Brunel University, Uxbridge UB8 7BQ, United Kingdom
4. Gatan UK, 25 Nuffield Way, Abingdon, Oxon OX14
1RL, United Kingdom