I-V, V-O characteristics and atomic force images of grain boundary Josephson junctions fabricated on SrTiO, bicrystal substrates were investigated. The half integer Shapiro steps and I, versus B curves show evidence of the inhomogeneous current distribution along the grain boundary junction. The dc SQUID formed on the grain boundary shows the expected V-O curve. The AFM images, R-T curves and IeRn product reveal sequential destructive deterioration of the junction originating from the underlying grooved substrate. The results are discussed.
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