Extreme doping of graphene

Extreme doping of two-dimensional (2d) van der Waals materials can lead to emergent phases and next generation electronic devices and photonics. This also requires clean and local charge control. Here, we demonstrate that the large work function narrow-band Mott insulator RuCl3 enables modulation doping of exfoliated graphene. We characterized the doping level in trilayer structure RuCl3/graphene/RuCl3 using Raman. The G and 2D peak of graphene showed significant upshifts, indicating that graphene is heavily doped. By performing Raman measurements at different excitation energies, we show that, with excitation wavelength longer than 633nm, the 2D peak can be suppressed by Pauli blocking as laser energy below the doping level.