Conductivity enhancement of ultrathin LaNiO3 films in superlattices

The resistance of superlattices composed of bilayers of ultrathin (similar to 4 unit cells) of LaNiO3 and similar to 3 unit cells of insulating SrTiO3 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. (C) 2010 American Institute of Physics. [doi:10.1063/1.3511738]