Current-voltage characteristics of Sigma 1 boundaries with and without cobalt ions in niobium-doped SrTiO3 bicrystals

Current-voltage (I-V) characteristics across Sigma 1 boundaries of Nb-doped SrTiO3, bicrystals were investigated with a special interest in the effect of an impurity ion, cobalt. The Sigma 1 boundary with cobalt ions was fabr icated by hot-joining technique after evaporating metallic cobalt onto the (001) plane used for a contact plane. High-resolution transmission electron microscopy (HREM) study associated with X-ray energy dispersive spectrosco py (EDS) revealed that cobalt solved and distributed around the Sigma 1 bou ndary which was perfectly joined without any second films. It was Found tha t the Sigma 1 boundary with cobalt ions exhibited a nonlinear I-V relations hip while the Sigma 1 boundary without cobalt ions showed a linear I-V rela tionship. This result indicates that the presence of cobalt itself at the b oundary can form a potential barrier irrespective of grain boundary coheren cy.