1. CEMES-CNRS, NanoSciences Group & MANA Satellite, 29 rue Jeanne Marvig, BP 94347, F-31055 Toulouse cedex 4, France
2. IMRE, A*STAR (Agency for Science, Technology and Research), 3 Research Link, 117602, Singapore
3. Université de Toulouse, UPS, 118 route de Narbonne, F-31062 Toulouse cedex 9, France