MgB2 film; SEM image; EDX; X-ray diffraction pattern
【摘要】
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 μm. The MgB2 thick film shows Tc (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.
