As-grown superconducting MgB_2 thin films have been grown on SrTiO_3(001),
MgO(001), and Al_2O_3(0001) substrates by a molecular beam epitaxy (MBE) method
with novel co-evaporation conditions of low deposition rate in ultra-high
vacuum. The structural and physical properties of the films were studied by
RHEED, XRD, electrical resistivity measurements, and SQUID magnetometer. The
RHEED patterns indicate three-dimensional growth for MgB_2. The highest T_c
determined by resistivity measurement was about 36K in these samples. And a
clear Meissner effect below T_c was observed using magnetic susceptibility
measurement. We will discuss the influence of B buffer layer on the structural
and physical properties.Comment: 9 pages with 4 figures, ISS2003 proceedin