Superconductivity of epitaxial MgB 2 thick films and MgB 2 nanowires grown by hybrid physical–chemical vapor deposition

Abstract

We have fabricated epitaxial MgB 2 thick films and MgB 2 nanowires by using hybrid physical–chemical vapor deposition (HPCVD) technique. Mg pellet and B 2H 6 gas were used as source substances. We used a special susceptor with a susceptor cap in order to obtain a high magnesium vapor pressure around the substrate. We were able to achieve very high growth rate of 0.17 μm/min. MgB 2 thick films and MgB 2 nanowires were grown on Al 2O 3 substrates at a low temperature. X-ray diffraction patterns showed epitaxial growth of MgB 2 thick films. Columnar structures of epitaxial MgB 2 thick films were observed by cross-sectional view transmission electron microscope (TEM) images. For the 1.7 μm thick film, the T c was observed to be 40.5 K with a J c of 1.5 × 10 6 A/cm 2 at 30 K. The MgB 2 nanowire observed by using scanning electron microscope (SEM) was 70–100 nm in diameter and 1–3 μm in length. A focused ion beam (FIB) was used to fabricate MgB 2 nano-bridge pattern on the MgB 2 thin film. The superconductivity of the MgB 2 nanowire was confirmed by using resistivity measurements.