▎ 摘　　要

A facile way to segregate wafer-size graphene with controllable layer number using Cu-Ni binary alloy under vacuum annealing condition is presented here. Increasing atomic percentage of Ni in Cu-Ni alloy was found to segregate thicker uniform graphene. To date, over 95% monolayer and 91% bilayer graphene films have been prepared by only changing atomic percentage of Ni in Cu-Ni alloy, respectively. The synergetic combination of the distinct carbon solubilities of Cu and Ni and the well-known segregation phenomenon is believed to be responsible for the formation of high-quality uniform few layer graphene. Together with the easy detachment from growth substrates, we believe this facile segregation technique will offer a great driving force for graphene research.