Atomic Heterointerfaces and Electrical Transportation Properties in Self-Assembled LaNiO3-NiO Heteroepitaxy

Abstract

Vertical nanostructure heteroepitaxy opens new opportunities for designing next-generation electronic devices due to the enthralling multifunction combinations and the abundant heterointerfaces manipulated effects. In this study, self-assembled heteroepitaxial thin films, vertically aligned metallic LaNiO3 (LNO) and semiconducting NiO with diverse heterointerfaces, are created and systematically investigated by advanced transmission electron microscopy. With the increase of LaNiO3 content, the LaNiO3 phases present as isolated islands encircled by the connected NiO nanoplates and eventually become the continuous matrix with embedded NiO nanopillars. The atomic heterointerface between NiO and LaNiO3 phases is determined to be [NiO2-LaO](LaNiO3)-LaO-[NiO](NiO), in which an extra La-O layer is enriched at the heterointerface. Besides, the formation mechanism of the heterointerface and antiphase boundaries observed in LaNiO3 phase is discussed. The electrical transport properties at room temperature can be tuned gradually by changing the volume ratio of constituents. The correlation among the insulator-to-metal transition, the carrier types associated with transport behaviors, and the heterostructure evolutions are explored. This study offers a desirable platform to design new multifunctional electronic devices based on the oxide heterojunctions.