[1] Karlsruhe Inst Technol, Inst Nanotechnol, D-76344 Eggenstein Leopoldshafen, Germany
[2] Univ Strasbourg, Inst Phys & Chim Mat Strasbourg IPCMS, CNRS, F-67034 Strasbourg 2, France
[3] Karlsruhe Inst Technol KIT, Inst Funct Inteifaces IFG, D-76344 Eggenstein Leopoldshafen, Germany
[4] Brazilian Ctr Res Energy & Mat CNPEM, Brazilian Nanotechnol Natl Lab LNNano, BR-13083970 Campinas, SP, Brazil