Ultra-thin HfAlO Nanofilms on Graphene Directly Deposited by Atomic Layer Deposition

In order to realize graphene-based devices, ultra-thin, uniform-coverage and pinhole-free dielectric films with high permittivity on top of graphene are required. Here we report the direct growth of HfAlO onto graphene by H
2
O-based atomic layer deposition (ALD). Al2O
3
-onto- HfO
2
stacks benefited the doping of Al
2
O
3
into HFO
2
matrixes more than HfO
2
-onto-Al
2
O
3
stacks did due to the micro-molecular property of Al
2
O
3
and high chemical activity of TMA. The capacitance and the relative permittivity of HfAlO was up to 1.18 µF/cm
²
and 12, respectively, indicating high quality of high-K films on graphene.