Communication-Reduced Off-Current of NbO2 by Thermal Oxidation of Polycrystalline Nb Wire

The origin of high leakage current in NbO2 is investigated on the basis of grain size and grain boundary distribution. We used thermally grown and sputtered NbO2 films on polycrystalline niobium microwires. The off-current of the thermally grown film was significantly decreased. This is attributed to the large size of grains in thermally grown film over sputtered one and better quality of oxide film could be grown in the thermal process than sputtering. Our assumptions are supported by Conductive Atomic Force Microscopy studies and simulations. In addition, by introducing 15 nm HfO2 dielectric layer further reduction of the off-current was achieved.