We have measured the tunneling characteristics of planar junctions fabricated on YBa2(Cu1-xFex)3O7 single crystals with different percentages of Fe substitutions. A liquid etched bath (1% Br in methanol, by volume) has been used to remove the degraded surfaces of the high T(c) superconductors. After a short air exposition, the junctions were completed by evaporating Pb thin film counterelectrodes through a metallic mask. In comparison with the undoped 90 K phase, the doped junctions show gap-like structures smeared and reduced in amplitude at about +/-25 mV, while a second feature at about +/-5 mV is present only for slightly doped samples. This fact seems to indicate that Fe is mainly substituting for Cu in the one-dimensional Cu-O chains.
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