Investigations of MgB2/MgO and MgB2/AIN heterostructures for Josephson devices

We report structural and transport proprieties of MgB2/MgO and MgB2/AlN multilayers for MgB2 Josephson junctions. The MgB2, layers were grown by,hybrid physical chemical vapor deposition (HPCVD). The epitaxial MgB2/MgO/MgB2 trilayers were grown in situ in the HPCVD system. The AlN layers were grown at room temperature by pulsed laser deposition, and the MgB2/AlN/MgB2 trilayers were deposited ex situ with the deposition of the AlN layer between the depositions of the top and bottom MgB2 layers. Although slightly less perfect than in films grown directly on sapphire and SiC substrates, excellent superconducting and transport properties were obtained in the MgB2 layers in both heterostructures. The result addressed only the first of many issues about the adequacy of using MgO and AlN as the barrier materials for all-MgB2 planar Josephson junctions, i.e. the ability to obtain good structural and superconducting properties in both electrode layers using the trilayer deposition process. It allows us to further investigate the conditions for better wetting and coverage of the insulator layers, as well as other critical issues in the fabrication of all-MgB2 planar Josephson junctions.