[1] Univ Manchester, Sch Phys & Astron, Manchester M13 9PL, Lancs, England
[2] Inst Microelect Technol, Chernogolovka 142432, Russia
[3] Univ Manchester, Manchester Ctr Mesosci & Nanotechnol, Manchester M13 9PL, Lancs, England
[4] TSC, Lancaster OL10 1DS, England
[5] Graphene Ind Ltd, Manchester M60 1QD, Lancs, England
[6] Radboud Univ Nijmegen, High Feild Magnet Lab, NL-6525 ED Nijmegen, Netherlands
[7] Univ Manchester, Sch Comp Sci, Manchester M13 9PL, Lancs, England