Direct growth of HfO2 on graphene by CVD

Abstract

Chemical vapor deposition (CVD) was applied to grow dielectric HfO2 layers on graphene/SiO2/Si and graphene/TiN/Si reference substrates directly, i.e., without a seed layer or any other functionalization of graphene. It was found that the presence of bilayer and (generally) multilayer graphene islands on nominally monolayer graphene strongly impacts the nucleation and the growth of HfO2. No damage inflicted by the CVD process on the graphene could be detected by Raman spectroscopy. According to x-ray diffraction, the films, grown on graphene at 400 °C and having thickness between 5 and 50 nm, were polycrystalline. Electrical measurements were performed for metal–insulator–metal (MIM) capacitors produced by evaporating Au and TiN top electrodes on the HfO2 film. Leakage currents were in the range of 10−8 A/cm2 at 1 V for 50 nm HfO2 grown on graphene, exceeding by one order of magnitude the currents measured for the reference HfO2/TiN MIM structures. The films grown on graphene have a dielectric constant of 17 with a quality factor of 50.