▎ 摘　　要

We demonstrate a chemical-vapor-deposition (CVD)-based approach for the direct synthesis of graphene on insulator with high-dielectric-constant (high-x). Rutile titanium dioxide (TiO2), an insulator with reported k value of 80-125, is selected as the growth-initiating layer for graphene. A two-step CVD process is shown to grow graphene directly on TiO2 crystals or exfoliated ultrathin TiO2 nanosheets without using any metal catalyst. Various material characterization techniques confirm the growth of few-to-monolayer of graphene. Annealing of the growth substrate at 1100 degrees C under atmospheric pressure, prior to the low-pressure CVD process, is needed for activating nucleation sites in subsequent graphene synthesis. Electrical behavior of a field-effect transistor fabricated on the graphene/TiO2 heterostructure shows p-type doping in the CVD-synthesized graphene. (C) 2012 Elsevier Ltd. All rights reserved.