Superconductivity of epitaxial MgB2 thick films and MgB2 nanowires grown by hybrid physical-chemical vapor deposition

Abstract

We have fabricated epitaxial MgB2 thick films and MgB2 nanowires by using hybrid physical-chemical vapor deposition (HPCVD) technique. Mg pellet and B2H6 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. MgB2 thick films and MgB2 nanowires were grown on Al2O3 substrates at a low temperature. X-ray diffraction patterns showed epitaxial growth of MgB2 thick films. Columnar structures of epitaxial MgB2 thick films were observed by cross-sectional view transmission electron microscope (TEM) images. For the 1.7 μm thick film, the Tc was observed to be 40.5 K with a Jc of 1.5 × 106 A/cm2 at 30 K. The MgB2 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 MgB2 nano-bridge pattern on the MgB2 thin film. The superconductivity of the MgB2 nanowire was confirmed by using resistivity measurements. © 2008 Elsevier B.V. All rights reserved.