Influence of cation off-stoichiometry on transport properties of metal/Nb-SrTiO_3 junctions

摘要

We investigated the influence of the cation off-stoichiometry on the transport properties of junctions consisting of a metal (Ti or Pt) and a Nb-doped SrTiO_3 (Nb-STO) epitaxial film. Ti/Nb-STO junctions with a Ti-deficient Nb-STO film show slightly asymmetric I-V characteristics and a large zero-bias differential junction resistance. Junctions with a Sr-deficient film, in contrast, exhibit nearly ohmic I-V characteristics and a differential resistance comparable to that of junctions with a stoichiometric film. We also found that the cation off-stoichiometry of the Nb-STO film has a strong influence on the rectifying and hysteric I-V characteristics of Pt/Nb-STO Schottky junctions. For Schottky junctions with the Ti-deficient film, the junction currents are largely reduced while the hysteric behavior remains. Junctions with the Sr-deficient film, on the other hand, have hysteric I-V characteristics that are comparable to those of junctions with the stoichiometric film. The results show the strong influence of the cation off-stoichiometry of the Nb-STO film on the junction properties. Based on the experimental results including transient behavior measurements, we discuss how the cation off-stoichiometry affects the transport properties of the metal/Nb-STO junctions.