Uniform MgB2 thin films grown on Si(111) and Al2O3(0001) substrates prepared by e-beam evaporation and in situ annealing methods

Abstract

MgB2 superconducting thin films on Si(111) and Al2O3(0001) substrates were prepared by high vacuum e-beam evaporation and two-step in situ annealing techniques. The precursor films [B(100 Å)/Mg(151 Å)]6/Al2O3 (or Si) were deposited at room temperature and 1x10−7 mbar of background vacuum, then annealed in situ at 630 °C for 30 min in an argon atmosphere of 150 Pa. The atomic force microscopy image showed that the films were uniform with grain sizes of about 100 nm. An extremely sharp superconducting transition with a width of 0.1 K and a zero-resistance temperature of 30.3 K was obtained, indicating a film of high uniformity and purity in its phase with perfect connection between the MgB2 grains.