Far-infrared study of substrate-effect on large scale graphene

From far-IR Drude absorption measurement we determine carrier density (N) and carrier scattering rate (Γ) of graphene deposited on buffer-layer/SiO2 composite substrate. Two types of buffer-layers, (1) polar dielectric oxide ZnO and SrTiO3 (2) organic thin film hexamethyldisilazane and polymethyl methacrylate (PMMA) were studied. N varies widely over 0.12–11.8(×1012 cm−2) range depending on the buffer-layer. In contrast Γ remains almost constant, ∼100 cm−1, irrespective of the buffer-layers. This indicates that carrier mobility (μ) of graphene depends on substrate through N, but not by Γ as commonly believed.