Crafting oxide superlattices with efficient electron doping induced by interfacial charge transfer

Charge doping represents one of the most successful approaches to regulating the properties of materials. Conventional chemical doping inevitably involves side effects from quenched disorder and is sometimes restricted by the choice of doping elements. In contrast, electrostatic doping makes it possible to inject carriers into materials in a clean manner; however, in materials with a high background carrier concentration, the working distance of electrostatic doping is rather limited due to the extremely short screening length. In this work, based on band-alignment considerations, we craft artificial superlattices of SrRuO3/NdNiO3 by intercalating a single-unit-cell charge-reservoir layer of SrRuO3 into a NdNiO3 matrix at varied periodicities. The designed electron transfer from SrRuO3 to NdNiO3 with accompanying orbital reconstruction is revealed by x-ray absorption spectroscopy. Such electron doping dramatically regulates the metal-insulator and antiferromagnetic transitions of NdNiO3. Moreover, bulklike E′ antiferromagnetic order is observed in the superlattice with NdNiO3 layers down to a single unit cell, which is related to the interfacial ion exchange enhanced by the strong electron transfer in the ultrathin limit. Our work raises the prospect of customizing artificial oxide materials with efficient modulation doping, which may lead to emergent functionalities unattainable in natural crystals.