1. Waterloo Institute for Nanotechnology, University of Waterloo, 200 University Avenue West, Waterloo, Ontario N2L 3G1, Canada
2. Department of Electrical and Computer Engineering, University of Waterloo, 200 University Avenue West, Waterloo, Ontario N2L 3G1, Canada
3. Department of Physics & Astronomy, University of Waterloo, 200 University Avenue West, Waterloo, Ontario N2L 3G1, Canada
4. Department of Systems Design Engineering, University of Waterloo, 200 University Avenue West, Waterloo, Ontario N2L 3G1, Canada
5. Shimco North America Inc., 75 Heroux Devtek Dr, Cambridge, Ontario N3E 0A7, Canada
6. School of Physics and Electronics, Henan University, No. 1 Jinming Street, Kaifeng, Henan 475001, P. R. China