Low-voltage Graphene/LiNbO₃memristors

Recent observations of domain wall conductivity in the LiNbO₃ thin films may facilitate the development of electrically-tunable resistive switching devices employing conductive domain walls as functional elements. In LiNbO₃ capacitors, several orders of magnitude modulation of resistance can be achieved by systematically changing the density of injected domain walls using voltage pulse amplitude above the coercive bias. However, a deleterious characteristic of this approach is a high-energy cost of polarization reversal due to high leakage current. Here, we demonstrate a new approach for tuning the device resistance by modulating the conductivity of domain walls rather than changing the domain configuration. Using the LiNbO₃ thin film capacitors with graphene top electrodes, we show that once the device is set to a specific poly-domain state, its resistance can be continuously tuned by application of sub-coercive voltage. The tuning mechanism is based on reversible transition between the conducting and insulating states of the domain walls due to the electrically-induced wall bending near the sample surface. The developed approach provides an energy-efficient way to realize resistive functionality without the need of the domain structure modification by high voltage pulses.