Scaling of Al2O3 dielectric for graphene field-effect transistors

We investigate the scaling of Al2O3 dielectric on graphene by atomic layer deposition (ALD) using ultra-thin, oxidized Ti and Al films as nucleation layers. We show that the nucleation layer significantly impacts the dielectric constant (k) and morphology of the ALD Al2O3, yielding k = 5.5 and k = 12.7 for Al and Ti nucleation layers, respectively. Transmission electron microscopy shows that Al2O3 grown using the Ti interface is partially crystalline, while Al2O3 grown on Al is amorphous. Using a spatially uniform 0.6 nm-thick Ti nucleation layer, we demonstrate graphene field-effect transistors with top dielectric stacks as thin as 2.6 nm.