1. Department of Physics, University of Alberta, Edmonton, Alberta T6G 2E1, Canada
2. Department of Physics and Astronomy, University of Calgary, Calgary, Alberta T2N 1N4, Canada
3. Nanotechnology Research Centre (NANO), National Research Council Canada (NRC), Edmonton, Alberta T6G 2M9, Canada
4. Department of Electronic Engineering, Maynooth University, W23 F2H6 Maynooth, County Kildare, Ireland