Temperature and gate voltage dependent electrical properties of graphene field-effect transistors

Temperature (T) and gate voltage sweep range (VGmax) dependent electrical properties of graphene field-effect transistors were investigated in the ambient atmosphere. With the increase of T from 300 to 380 K, the charge neutrality point (CNP) in the transfer characteristic curve (ID-VG) was shifted negatively from the positive voltage to near zero, which might be mainly due to the desorption of water adsorbates from the graphene surface and other thermally activated processes at the graphene/SiO2 interface at high T. Accompanying the CNP shift is the semiconducting behavior of the temperature-dependent conductivity, observed not only in the low carrier density region near the CNP, but also in the high carrier density region. The variations in the position and magnitude of the CNP in the ID-VG hysteresis loops were linearly enhanced by increasing either T or VGmax, which are explained in terms of the trapping/detrapping process and the chemical redox reaction at the graphene-oxide interface, as well as the thermally activated mobile ions movement in the dielectric layer.