[1] CSIC, Inst Ciencia Mat Barcelona ICMAB, Bellaterra 08193, Catalonia, Spain
[2] Univ Complutense Madrid, Dept Fis Aplicada 3, E-28040 Madrid, Spain
[3] Oak Ridge Natl Lab, Mat Sci & Technol Div, Oak Ridge, TN 37831 USA
[4] Univ Zaragoza, Inst Nanociencia Aragon INA ARAID, Lab Microscopi Avanzadas LMA, Zaragoza 50018, Spain
[5] Catholic Univ Louvain, Inst Condensed Matter & Nanosci Bio & Soft Matter, B-1348 Louvain, Belgium
[6] It4ip SA, B-7180 Seneffe, Belgium