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

We have studied the epitaxial growth of bismuth overlayers on Si(111) 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 7×7 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)-1×1 surface. The films prepared on Si(111)-α-√3×√3-Bi or on Si(111)-β-√3×√3-Bi do not show as good quality as those on Si(111)-7×7. Thus, the initial disordered wetting layer formed on the 7×7 surface successfully accommodates the large 18% lattice mismatch between the Si(111) and Bi(0001) planes and allows the 2D nanocrystal to grow laterally.