1. School of Electrical and Computer Engineering, Cornell University, Ithaca, New York 14853, USA
2. Department of Materials Science and Engineering, Cornell University, Ithaca, New York 14853, USA
3. Novel Crystal Technology, Inc., Sayama, Saitama 350-1328, Japan
4. Center for Micro-Nano Technology, Hosei University, Koganei, Tokyo 184-0003, Japan
5. Kavli Institute at Cornell for Nanoscale Science, Cornell University, Ithaca, New York 14853, USA