Conductivity enhancement of ultrathin LaNiO_3 films in superlattices

摘要

The resistance of superlattices composed of bilayers of ultrathin (~4 unit cells) of LaNiO_3 and ~3 unit cells of insulating SrTiO_3 is explored as a function of temperature and the number of bilayers. All superlattices with more than one bilayer are metallic, whereas a single bilayer is insulating. Two possible interpretations of the electrical characteristics of the superlattices are discussed. The first model involves conduction in parallel-connected layers, whereas the second model assumes coupling of layers, each of which is near the percolation threshold for a metal-insulator transition.