NEW BARIUM-INDUCED SURFACE RECONSTRUCTIONS ON SI(111)

The growth of Ba on Si(111)7 x 7 at room temperature proceeds in a lay er-by-layer fashion up to at least two full layers. Upon subsequent an nealing, four new sub-monolayer surface reconstructions can be identif ied. The (3 x 1), (5 x 1) and (2 x 8) reconstructions are formed at ab solute coverages not larger than 0.35, 0.50 and 0.65 monolayer (ML), r espectively. A (root 3 x root 3)R30 degrees reconstruction co-exists w ith each of these phases and possibly comprises a pseudo-centered orth orhombic BaSi2(100) layer. Epitaxial BaSi2 is formed under supersatura tion conditions at substrate temperatures near 600 degrees C.