Thin films of MgB2 were prepared on polished sapphire C(001) single crystal substrates by using electron beam evaporation without any post-annealing. The background pressure was controlled to less than 10−6Pa and the deposition conditions were varied to investigate the effects of the growth temperature and the chemical composition of MgB2 thin films on the pinning characteristics. It was found that superconducting MgB2 thin films could be obtained even at very low substrate temperature of 120C. With raising the deposition temperature up to 240C, TC increased to 33K in the MgB2 thin films with the stoichiometric composition (Mg:B = 1:2). However, ΔM in the M–H curve of the film deposited at 240C was smaller than that of the film at 210C. It was confirmed that the ΔM value was affected by the grain size of MgB2. It was also clarified that the Mg poor compositions make the c-axis length short and that the some defects introduced by the Mg deficiency acted as pinning centers.

Fabrication of MgB2 Thin Films by Electron Beam Evaporation Technique. K.Nagatomo, T.Doi, Z.Mori, H.Kitaguchi, Y.Kobayashi, Y.Hakuraku, K.Saitoh, M.Okada: Physica C, 2005, 426-431[2], 1459-63