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

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 1×10^-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. [ABSTRACT FROM AUTHOR]