Sandwich-type all- MgB2 Josephson tunnel junctions (MgB2 AlOx MgB2) have been fabricated with as-grown MgB2 films formed by molecular-beam epitaxy. The junctions exhibit substantial superconducting current (Ic RN product ~0.8 mV at 4.2 K), a well-defined superconducting gap (Δ=2.2-2.3 mV), and clear Fraunhofer patterns. The superconducting gap voltage of Δ agrees well with the smaller gap in the multigap scenario. The results demonstrate that MgB2 has great promise for superconducting electronics that can be operated at T~20 K.
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