Ultrathin Al Oxide Seed Layer for Atomic Layer Deposition of High-\kappa Al_2O_3 Dielectrics on Graphene

Due to the lack of surface dangling bonds in graphene, the direct growth of high-\kappa films via atomic layer deposition (ALD) technique often produces the dielectrics with a poor quality, which hinders its integration in modern semiconductor industry. Previous pretreatment approaches, such as chemical functionalization with ozone and plasma treatments, would inevitably degrade the quality of the underlying graphene. Here, we tackled this problem by utilizing an effective and convenient physical method. In detail, the graphene surface was pretreated with the deposition of thermally evaporated ultrathin Al metal layer prior to the Al_2O_3 growth by ALD. Then the device was placed in a drying oven for 30 min to be naturally oxidized as a seed layer. With the assistance of an Al oxide seed layer, pinhole-free Al_2O_3 dielectrics growth on graphene was achieved. No detective defects or disorders were introduced into graphene by Raman characterization. Moreover, our fabricated graphene top-gated field effect transistor exhibited high mobility (\sim 6200 cm^2V^-1s^-1) and high transconductance (\sim 117 μS). Thin dielectrics demonstrated a relative permittivity of 6.5 over a large area and a leakage current less than 1.6 pA/μm^2. These results indicate that Al oxide functionalization is a promising pathway to achieve scaled gate dielectrics on graphene with high performance.