A Study on the Components of MgB2 Thick Film Prepared via HPCVD

Abstract

Superconducting MgB₂ thick film has been prepared via hybrid physical chemical vapor deposition method on Al₂O₃ (0001) substrate by using B₂H₆ and magnesium ingot as raw materials reacted from 730 to 830?C for 40 min under 20 to 30 kPa. Its thickness is about 40 ?m. The MgB₂ thick film shows T_c (onset) = 39.0 K and Tc (0) = 37.2 K. X-ray diffraction pattern shows that the film grown along (101) direction has small amount of impurities of Mg and MgO. Scanning electron microscopy and energy dispersive X-ray spectroscopy indicated that these impurities existed indeed and were Mg rich. The MgO film was formed on the surface of the MgB₂ thick film to further protect the sample from oxidation. We presented a new mechanism for the formation of the thick film.