Rectifying NdNiO3∕Nb:SrTiO3 junctions as a probe of the surface electronic structure of NdNiO3

We have studied the electronic properties of junctions formed between Nb-doped SrTiO3 substrates, an n-type semiconductor, and NdNiO3 films, which exhibit a strong first-order phase transition from a high temperature paramagnetic metal to a low temperature antiferromagnetic insulator. Although the junctions are rectifying at all temperatures, the current-voltage and capacitance characteristics show no indication of the metal-insulator transition clearly observed in the films. This suggests that the surface electronic structure of NdNiO3 is distinct from the interior of the film and does not undergo the bulk transition.