1. Department of Physics, University of Alberta, Edmonton, Alberta T6G 2J1, Canada
2. Metrology Research Centre, National Research Council of Canada, 1200 Montreal Road, Ottawa, Ontario K1A 0R6, Canada
3. Quantum Silicon, Inc., Edmonton Alberta T6G 2M9, Canada
4. Nanotechnology Research Centre, National Research Council Canada, Edmonton, Alberta T6G 2M9, Canada