Sectional structures and electrical properties of ultrathin NbN/MgO bilayers on Si(100)

NbN/MgO bilayers deposited on Si(100) substrates by rf-sputtering were studied using cross-sectional transmission electron microscopy (XTEM). The XTEM results reveal that the 10-nm-thick MgO layer forms two layers of different structures, i.e., an amorphous layer (∼4 nm) and a highly (100) oriented polycrystalline layer (∼6 nm). We also found that the structure of MgO underlayers exhibits a strong effect on Tc of on-deposited NbN layers.