Fabrication and characterization of NbN/AlN/NbN junction on MgO(001) and AlN/NbN bilayer on MgO(111) substrates

Using direct current (DC) or radio frequency (RF) magnetron sputtering techniques, NbN/AlN/NbN junctions or AlN/NbN bilayers are prepared on single crystal MgO [001] or MgO (111) substrates respectively, both at ambient substrate temperatures. The crystalline structures of such multilayers are characterized layer-by-layer using X-ray diffraction and transmission electron microscopy (TEM). Interestingly, the AlN barrier in NbN/AlN/NbN/ MgO [001] is amorphous while the NbN/AlN/NbN/MgO (111) is single-crystalline with [001] orientation. The electrical properties of these two structures are compared. Also discussed are the DC and high frequency behavior of NbN/AlN/NbN/ MgO [001] junction.