1. Research Center for Integrated Quantum Electronics, Hokkaido University, Kita-13 Nishi-8, Kita-ku, 060-8628 Sapporo, Japan
2. Surface Physics and Nanostructures Department, Institute of Physics-CND, Silesian University of Technology, Konarskiego 22B, 44-100 Gliwice, Poland
3. Institute of Physics, Polish Academy of Sciences, al. Lotnikow 32/46, 02-668 Warsaw, Poland
4. Institute of Electron Technology, al. Lotnikow 32/46, 02-668 Warsaw, Poland