Lattice and grain-boundary diffusions of impurity atoms in BaSi2 epitaxial layers grown by molecular beam epitaxy

Al or B layers of a few hundreds of nm in thickness deposited on BaSi2 epitaxial films on Si(1 1 1) substrates were annealed at different temperatures, and the diffusion coefficients of Al and B were evaluated using secondary ion mass spectrometry with O2+. We also investigated the effect of post annealing (850 °C, 10 min) of BaSi2 films on the diffusion coefficients. It was found that both the lattice diffusion and the grain boundary diffusion were decreased by the post-annealing. The plan-view transmission electron microscopy images revealed that the grain size was increased from approximately 0.2 to 0.6 μm by the annealing, and the X-ray diffraction intensities also increased. The activation energies of lattice and grain boundary diffusions in the post-annealed BaSi2 are 0.63 eV and 0.58 eV for Al, and 4.6 eV and 4.4 eV for B, respectively.