1. Thayer School of Engineering, Dartmouth College, Hanover, NH 03755, USA.
2. Institute of Condensed Matter and Nanosciences (IMCN), Université Catholique de Louvain, Chemin des Étoiles 8, Louvain-la-Neuve B-1348, Belgium.
3. Department of Physics, Ah-Najah National University, Nablus, Palestine.
4. Department of Materials Science and Engineering, University of California, Berkeley, Berkeley, CA 94720, USA.
5. Materials Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, CA 94720, USA.
6. Molecular Foundry Division, Lawrence Berkeley National Laboratory, Berkeley, CA 94720, USA.
7. Department of Electrical Engineering and Computer Sciences, University of California, Berkeley, Berkeley, CA 94720, USA.
8. Department of Physics, University of California, Berkeley, Berkeley, CA 94720, USA.