Effect of ferroelectric substrate on carrier mobility in graphene field-effect transistors

Effect of LiNbO3 ferroelectric substrate on the carrier mobility in top gated graphene field-effect transistors (G-FETs) is demonstrated. It is shown that, at the same residual concentration of the charge carriers, the mobility in the G-FETs on the LiNbO3 substrate is higher than that on the SiO2/Si substrate. The effect is associated with reduction of Coulomb scattering via screening the charged impurity field by the field induced in the ferroelectric substrate, but significant only for mobilities below 1000 cm2/V s. Raman spectra analysis and correlations established between mobility and microwave loss tangent of the Al2O3 gate dielectric indicate that the charged impurities are located predominantly at the gate dielectric and/or at the gate dielectric/graphene interface and are likely associated with oxygen vacancies.