Studies on H2O-based Atomic Layer Deposition of Al2O3 Dielectric on Pristine Graphene

Al2O3 films were deposited directly onto the surface of graphene by H2O-based atomic layer deposition (ALD) method, where physically absorbed water molecules acted as oxidant and the growing temperature changed from 60 degrees C to 260 degrees C. The morphology of Al2O3 films was characterized by atomic force microscope (AFM). AFM images revealed that the distribution of physically adsorbed H2O molecules on the surface of graphene decided the morphology of Al2O3 film, and conformal and uniform Al2O3 film was achieved with the root mean square (RMS) roughness of 0.26 nm when the growing temperature was around 100-130 degrees C. X-ray photoelectron spectroscopy (XPS) analysis showed that the O/Al ratio was close to stoichiometric condition of 1.5. Raman spectroscopy analysis revealed that H2O-based ALD process did not destroy the structure of graphene. The growing temperature in the H2O-based ALD process had significant impact on the initial nucleation and the growth of Al2O3 films.