Epitaxial growth of single-crystal ultrathin films of bismuth on Si(111)

We have studied the epitaxial growth of bismuth overlayers on Si(lll) surfaces by in situ reflection high-energy electron diffraction (RHEED) and scanning tunneling microscopy (STM). Lateral growth of texture two-dimensional (2D) nanocrystals takes place after the formation of an initial disordered wetting layer on the 7 x 7 DAS structure. After the coalescence of the texture 2D nanocrystals, alignment in their azimuthal orientation takes place. At slightly more than 15 monolayers, the growth front of the overlayer exhibits a perfectly long-range ordered Bi(0001)-1 x 1 surface. Toe films prepared on Si(111)-alpha-root 3 x root 3-Bi or on Si(111)-beta-root 3 x root 3-Bi do not show as good quality as those on Si(111)-7 x 7. Thus, the initial disordered wetting layer formed on the 7 x 7 surface successfully accommodates the large 18% lattice mismatch between the Si(lll) and Bi(0001) planes and allows the 2D nanocrystal to grow laterally.