1. Department of Materials Science and Engineering, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA
2. Semilab Semiconductor Physics Laboratory Co. Ltd., Budapest 1117, Hungary
3. Center for Advancing Materials Performance from the Nanoscale, State Key Laboratory for Mechanical Behavior of Materials, Xi'an Jiaotong University, Xi'an 710049, China
4. Department of Nuclear Science and Engineering, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA
5. Center for Nanoscale Systems, Harvard University, Cambridge, Massachusetts 02138, USA