1. Department of Physics and Astronomy, York University, Toronto, Ontario M3J 1P3, Canada
2. Department of Electrical Engineering and Computer Science, York University, Toronto, Ontario M3J 1P3, Canada
3. Department of Engineering, University of Cambridge, Cambridge, United Kingdom
4. Institute of Physics, Chemnitz University of Technology, Chemnitz, Germany
5. Institute of Ion Beam Physics and Materials Research, Helmholtz-Zentrum Dresden-Rossendorf, Dresden, Germany