Electronic structure of Te- and As-covered Si(211)

Electronic and atomic structures of the clean and As- and Te-covered Si(211) surface are studied using pseudopotential density-functional method. The clean surface is found to have $(2\ifmmode\times\else\texttimes\fi{}1)$ and rebonded $(1\ifmmode\times\else\texttimes\fi{}1)$ reconstructions as stable surface structures, but no $\ensuremath{\pi}$-bonded chain reconstruction. Binding energies of As and Te adatoms at a number of symmetry sites on the ideal and $(2\ifmmode\times\else\texttimes\fi{}1)$ reconstructed surfaces have been calculated because of their importance in the epitaxial growth of CdTe and other materials on the Si(211) surface. The special symmetry sites on these surfaces having the highest binding energies for isolated As and Te adatoms are identified. But more significantly, several sites are found to be nearly degenerate in binding-energy values. This has important consequences for epitaxial growth processes. Optimal structures calculated for 0.5 monolayer of As and Te coverage reveal that the As adatoms dimerize on the surface while the Te adatoms do not. However, both As- and Te-covered surfaces are found to be metallic in nature.