[1] CSIC, Catalan Inst Nanosci & Nanotechnol ICN2, Campus UAB, Barcelona 08193, Spain
[2] Barcelona Inst Sci & Technol, Campus UAB, Barcelona 08193, Spain
[3] UMR CNRS 8520, Inst Elect Microelect & Nanotechnol, Ave Poincare,CS 60069, F-59652 Villeneuve Dascq, France
[4] Luxembourg Inst Sci & Technol, Mat Res & Technol MRT Dept, 5 Ave Hauts Fourneaux, L-4362 Esch Sur Alzette, Luxembourg
[5] Univ Toulouse, CNRS, Lab Anal & Architecture Syst, 7 Ave Colonel Roche, F-31400 Toulouse, France
[6] Univ Zaragoza, Inst Nanociencia Aragon INA ARAID, Lab Microscopias Avanzadas, Zaragoza 50018, Spain
[7] Univ Zaragoza, Dept Fis Mat Condensada, Zaragoza 50018, Spain
[8] Inst Catalana Recerca & Estudis Avancats ICREA, Barcelona 08010, Catalonia, Spain
[9] Australian Natl Univ, Res Sch Phys & Engn, Dept Elect Mat Engn, GPO Box 4, Canberra, ACT 0200, Australia
[10] Univ Paris Saclay, CEA Saclay, CNRS, SPEC,CEA, F-91191 Gif Sur Yvette, France