1. Institut of Materials Science of Barcelona, CSIC, Campus UAB, 08193 Bellaterra, Barcelona, Spain
2. Catalan Institute of Nanoscience and Nanotechnology (ICN2), CSIC and BIST, Campus UAB, Bellaterra, 08193 Barcelona, Spain
3. Institut of Microelectronics of Barcelona-Center National of Microelectronics, CSIC, Campus UAB, 08193 Bellaterra, Barcelona, Spain