Time-dependent transport characteristics of graphene tuned by ferroelectric polarization and interface charge trapping.

Abstract

Graphene-based field effect transistors (FETs) were fabricated by employing ferroelectric Pb(Mg1/3Nb2/3)O3-PbTiO3 (PMN-PT) as a gate insulator. The co-existing effects of ferroelectric gating and interface charge trapping on the transport properties of graphene were investigated with respect to the FET structure. The sheet resistance (Rs) of graphene shows a slight decay under a small applied voltage, which is much less than the coercive voltage of the ferroelectric PMN-PT, suggesting non-negligible charge trapping effects. Moreover, when the applied voltage is increased up to a value larger than the coercive voltage, Rs exhibits three states: an initial rapid change, followed by a slow nearly exponential evolution, and finally a saturated state either during the applied voltage is retained or after it is released. In particular, a high-resistance state is finally reached due to the ferroelectric gating, implying that ferroelectric effects dominate this process. The underlying physical mechanism was fully investigated to effectively address the observed evolution of time-dependent Rs. Such a finding provides us an opportunity to understand the co-existing effects of ferroelectric gating and charge trapping and tune the transport properties of graphene through the interface effects.