Preparation of Large Area NbN/AlN/NbN Josephson Junctions

AℓN has been used as a barrier material in large josephson junctions. The chemical and structural compatibility of AℓN with NbN make it possible to fabricate NbN/AℓN/NbN junctions by sequential reactive sputtering in a common Ar and N2 atmosphere. In a junction with an area of about 1.0×1.0 mm2, having a transition temperature of 14.5K. the measured I–V and first derivative curves yield a sum gap value of about 3.0 meV.