Rolling Up Transition Metal Chalcogenides/Oxide Heterostructures Enables Polarity-Tunable and High-Switchable Memristors.

Harnessing transition metal dichalcogenides (TMDCs) for memristors provides a promising pathway toward high-density data storage and neuromorphic functionalities. Yet the single operation mode and insufficient on/off ratio extremely restrict the ultimate device performance. Here, we design and construct a high-order superlattice-based memristor by rolling up oxide/TMDCs heterostructures, which exhibits tunable resistive switching polarity and a high on/off ratio. Four types of heterostructures are created via fine-controlled oxygen plasma to in situ oxidize the top few layers into uniform transition metal oxide. Capillary forces in organic reagents are utilized to drive these heterostructures to spontaneously roll up. The as-formed high-order oxide/TMDCs superlattices with alternately stacked TMDCs and oxides are clearly resolved by the cross-section scanning transmission electron microscope and corresponding elemental mappings. With pre-set oxide layers supplying mobile oxygen atoms, bipolar resistive switching of the high-order superlattice-based memristors is realized in vertical tunneling current measurements. In contrast, when the top and bottom electrodes are arranged in an interleaved configuration, the spatial confinement of conductive filaments converts the switching behavior into a unipolar mode. Furthermore, this polarity-tunable memristor exhibits an outstanding on/off ratio of approximately 107 and a robust multilevel resistance performance. Our work opens a new avenue for the fundamental design of high-performance and multimodal memristors.