Ge-intercalated graphene: The origin of the p-type to n-type transition T. P. Kaloni, M. Upadhyay Kahaly, Y. C. Cheng and U. Schwingenschlögl EPL, 99 5 (2012) 57002 Published online: 12 September 2012 DOI: 10.1209/0295-5075/99/57002