1. IMEP-LAHC (UMR CNRS/INPG/UJF 5130), Grenoble INP Minatec, 3 Parvis Louis Néel, BP 257, F-38016 Grenoble, France
2. Oak Ridge National Laboratory, One Bethel Valley Road, Oak Ridge, Tennessee 37831-6493, United States
3. CIN2 (CSIC-ICN) Barcelona, Campus Universitat Autonoma de Barcelona, E-08193 Bellaterra, Spain
4. CIN2 (ICN-CSIC) and Universitat Autonoma de Barcelona, Catalan Institute of Nanotechnology, Campus de la UAB, 08193 Bellaterra (Barcelona), Spain
5. ICREA, Institució Catalana de Recerca i Estudis Avancats, 08010 Barcelona, Spain