  We investigate the structural damage of graphene underlying dielectrics (HfO2
and Al2O3) by remote plasma-enhanced atomic layer deposition (PE-ALD).
Dielectric film is grown on bilayer graphene without inducing significant
damage to the bottom graphene layer. Based on Raman spectra, we demonstrate
that the bottom graphene layer has the salient features of single layer
graphene. During the initial half-cycle PE-ALD, the upper graphene layer reacts
with the metal precursor, forming uniform nucleation islands or an active
metallic carbide layer. After monolayer dielectric coverage, the bottom
graphene layer has additional protection. The upper graphene layer serves as a
sacrificial layer, which not only promotes the adhesion of dielectric on
graphene, but also protects the lattice symmetry of the bottom graphene layer.
Our results indicate that bilayer graphene allows for controlling/limiting the
degree of defect during the ALD of dielectrics and could be a good starting
material for building filed effect transistors and sensing devices.
