Tunneling measurements ofNd1.85Ce0.15CuOx

Tunneling spectroscopy measurements have been carried out on the electron-doped oxide superconductor ${\mathrm{Nd}}_{1.85}$ ${\mathrm{Ce}}_{0.15}$ ${\mathrm{CuO}}_{\mathrm{x}}$. Surfaces of a polycrystalline bulk sample of the compound were probed at low temperatures by a point-contact technique using Al as the counterelectrode. The differential conductance curve taken of the junctions exhibited a relatively well-pronounced gaplike structure near 5 mV at temperatures from 4.2 up to about 15 K. Taking the peak of the structure with the estimated $T_c$ of the dominant phase of the sample, we obtain the reduced energy gap 2Δ(0)/$k_B$ $T_c$ of 5.5±1.2, which is consistent with values we have obtained previously from the hole-doped oxide superconductors.