1. Helmholtz-Zentrum Dresden-Rossendorf, Institute of Ion Beam Physics and Materials Research, 01328 Dresden, Germany
2. Institute of Applied Physics, Technical University of Dresden, 01062 Dresden, Germany
3. Leibniz-Institut für Kristallzüchtung (IKZ), 12489 Berlin, Germany
4. Korea Research Institute of Standards and Science, 34113 Daejeon, Republic of Korea
5. Department of Nano Science, University of Science and Technology (UST), Daejeon 34113, Republic of Korea