Intrinsic High-Order Ionic Superlattices in Two-Dimensional Oxide Perovskites

Abstract A high-order superlattice is desirable in emerging classes of semiconductors because it allows functionalities beyond the reach of existing materials. Despite their beneficial features, certain shortcomings, such as the poor interface between heterostructures and laborious time-consuming fabrication for stacking high-ordered layers, still need to be addressed. Here, we present intrinsic high-order ionic layered superlattices in two-dimensional layered Dion-Jacobson phase oxide perovskites. The atomically clean interfaces between neighbouring layers ensure unique quantum mechanical properties derived from the quantum wells of ionic layered superlattices. The resultant anomalous charging behaviour offers tenable conductivity enhancements and realises artificial synaptic devices modulated by both optical and electrical stimuli. We also demonstrate the high tunability of the ionic composition and number of layers of the two-dimensional layered oxide perovskites, resulting in tailored electrical properties. Our study promises a new class of ideal superlattices and their great potential as a novel two-dimensional building block for device applications.