Bidirectional interdependency between graphene doping level and ferroelectric polarization is demonstrated in graphene/PbZr0.2Ti0.8O3 hybrid structures. The polarization of the PbZr0.2Ti0.8O3 can be effectively switched with graphene electrodes and can in turn alter carrier type and density in the graphene. A complete reversal of the current-voltage hysteresis direction is observed in the graphene when external environmental factors are minimized, converting p-type graphene into n-type with an estimated carrier density change as large as ~10(13) cm(-2). Nonvolatility and reversibility are also demonstrated.

Tuning graphene conduction states with the remnant polarization of ferroelectric oxides holds much promise for a range of low-power transistor and memory applications. However, understanding how the ferroelectric polarization affects the electronic properties of graphene remains challenging because of a variety of intricate and dynamic screening processes that complicate the interaction. Here, we report on a range of slow electrical conductance relaxation behavior in graphene-ferroelectric field-effect transistors with the extreme case leading to the convergence of two polarization-induced states. Piezoresponse force microscopy through the graphene channel reveals that the ferroelectric polarization remains essentially unchanged during this conductance relaxation. When measured in vacuum, the conductance relaxation is significantly reduced, suggesting equilibration with adsorbates from the ambient atmosphere that can cause charge transfer to and from graphene to be the origin of the slow relaxation.

The continuing revolutionary success of mobile computing and smart devices calls for the development of novel, cost- and energy-efficient memories. Resistive switching is attractive because of, inter alia, increased switching speed and device density. On electrical stimulus, complex nanoscale redox processes are suspected to induce a resistance change in memristive devices. Quantitative information about these processes, which has been experimentally inaccessible so far, is essential for further advances. Here we use in operando spectromicroscopy to verify that redox reactions drive the resistance change. A remarkable agreement between experimental quantification of the redox state and device simulation reveals that changes in donor concentration by a factor of 2-3 at electrode-oxide interfaces cause a modulation of the effective Schottky barrier and lead to >2 orders of magnitude change in device resistance. These findings allow realistic device simulations, opening a route to less empirical and more predictive design of future memory cells.