Structural analysis of the beta -SiC(100)-c(2 x 2) surface reconstruction by automated tensor low-energy electron diffraction.

Abstract

The atomic structure of the \ensuremath{\beta}-SiC(100)-c(2\ifmmode\times\else\texttimes\fi{}2) surface was analyzed using dynamical calculations of low-energy electron-diffraction intensities. The c(2\ifmmode\times\else\texttimes\fi{}2) surface was prepared in ultrahigh vacuum by two different methods. The first utilized the removal of surface silicon by high-temperature annealing in ultrahigh vacuum. The second route utilized the deposition of surface carbon by exposing the stoichiometric (2\ifmmode\times\else\texttimes\fi{}1) surface at 1125 K to ${\mathrm{C}}_{2}$${\mathrm{H}}_{4}$. Our results showed that both methods produced a surface terminated with ${\mathrm{C}}_{2}$ groups in staggered silicon bridge sites. Weak silicon dimer bonds were found in the second atomic layer of the c(2\ifmmode\times\else\texttimes\fi{}2) surface produced by silicon sublimation, but not for the c(2\ifmmode\times\else\texttimes\fi{}2) surface produced by ${\mathrm{C}}_{2}$${\mathrm{H}}_{4}$ exposure. We postulate that hydrogen, released by the thermal decomposition of ${\mathrm{C}}_{2}$${\mathrm{H}}_{4}$, saturated silicon dangling bonds in the second atomic layer, suppressing dimer formation.