Preparation and Characteristics of Multilayer Magnesium Diboride Superconducting Films via CVD Method

In this work we present the technology of preparing multilayer MgB2 superconducting films via CVD method. The first layer of the MgB2 superconducting film was obtained by two-step method: growthing the precursor boron film on a polycrystalline Al2O3 substrate first, then post annealing the film in magnesium ambient, thus we got the first layer of MgB2 film. After that a pure boron film was deposited on the MgB2 film , acting as the medium insulating layer, finally the second layer of the MgB2 superconducting film was formed by in-situ growth, evaporated magnesium atoms and boron atoms that decomposed from diborane met near the substrate and generated the second layer of the MgB2 superconducting film. The square resistance of the boron medium insulation layer is higher than 20 MΩ. The transition temperature of the both superconducting films was above 38 K, and the temperature for zero resistance is above 37 K. We found that different thickness of the B layer made different I-V curve between two superconducting films, which is very important for the use of Josephson junction. More meaningful results can be expected as the experiment goes on.