▎ 摘　　要

In this work, we report the electron mobility and electron density of three graphene field effect transistors using a 280 nm titanium dioxide dielectric layer and a graphene channel of area 300 x 300 mu m(2). We achieve electron mobilities up to 1877 cm(2)/V and the Dirac point appears in small gate voltages, as compared to similar SiO2 transistors. Also, we obtain the TiO2 surface roughness through profilometry and confirm that electron mobility is inversely proportional to the channel's surface roughness.