The graphene used in this study was synthesized on copper foil
by low pressure chemical vapor deposition (LPCVD) [24,25], with
methane as carbon source. After synthesis, it was transferred onto
heavily doped Si substrate with a 100-nm-thick SiO2 capping layer.
The samples were then bombarded by boron ions to doses ranging
from 0 to 5 1014 cm2 at a fixed energy of 32 keV. Those boron
ions was introduced by an implanter (Varian 350D) which is widely