[1] Univ Castilla La Mancha, Appl Phys IRICA, Ciudad Real, Spain
[2] Inst Bioengn & Nanotechnol, Singapore, Singapore
[3] Catalan Inst Nanosci & Nanotechnol ICN2, Barcelona, Spain
[4] NCSR Demokritos, Inst Nanosci & Nanotechnol, Athens, Greece
[5] Uppsala Univ, Dept Engn Sci, Uppsala, Sweden