1. CMEMS—UMINHO, Universidade do Minho, Campus Azurem, 4804-533 Guimaraes, Portugal
2. Centro de Física das Universidades do Minho e do Porto (CF-UM-UP), Campus de Gualtar, 4710-057 Braga, Portugal
3. Department of Surface and Plasma Science, Faculty of Mathematics and Physics, Charles University, V Holešovičkách 2, 18000 Prague 8, Czech Republic
4. National Institute of Materials Physics, 105 bis Atomistilor, 077125 Magurele, Romania
5. School of Engineering and Materials Science, Queen Mary University of London, Mile End Road, London E1 4NS, U.K.
6. Department of Materials Science, University of Milano-Bicocca, via R. Cozzi 55, I-20125 Milano, Italy