Polarity-driven nickel oxide precipitation in LaNiO3-LaAlO3 superlattices

We have studied the microstructure of LaNiO3-LaAlO3 superlattices using transmission electron microscopy in combination with electron energy loss spectroscopy. In superlattices grown on non-polar SrTiO3 substrates, nanometer-sized NiO precipitates form directly at the interface between the substrate and the initial LaNiO3 layer, while control measurements on polar substrates show no NiO. Because of the drastically different electronic properties of NiO and LaNiO3, such precipitates can strongly affect measurements on atomically thin LaNiO3-based films and multilayers on SrTiO3. In general, polarity-driven secondary phase formation should be carefully evaluated as a possible consequence of the polarity mismatch at metal-oxide interfaces. (C) 2011 American Institute of Physics. [doi: 10.1063/1.3663568]