Atomic structure of Si-rich6H‐SiC(0001¯)‐2×2surface

Abstract

The atomic structure of the Si-rich $6\mathrm{H}\text{\penalty1000-\hskip0pt}\mathrm{SiC}(000\overline{1})\text{\penalty1000-\hskip0pt}2\ifmmode\times\else\texttimes\fi{}2$ surface has been determined by high-resolution medium energy ion scattering (MEIS) and photoelectron spectroscopy using synchrotron-radiation-light (SR-PES). The MEIS analysis reveals the fact that Si adatoms (0.2--0.3 ML) overlie a Si adlayer (0.8--0.9 ML) sitting on the bulk-truncated surface $(1\phantom{\rule{0.3em}{0ex}}\mathrm{ML}=1.22\ifmmode\times\else\texttimes\fi{}{10}^{15}\phantom{\rule{0.3em}{0ex}}\text{atoms}∕{\mathrm{cm}}^{2})$. In fact, we observed two surface-related components in the Si $2p$ core level spectra corresponding to the adatom and the adlayer Si atoms and the intensity ratio of the former to the latter was $\ensuremath{\sim}1∕3$. On the other hand, the C $1s$ core level observed has the bulk component only. We propose an adatom-adlayer model satisfying the $2\ifmmode\times\else\texttimes\fi{}2$ surface reconstruction, threefold symmetry and the results obtained by MEIS and SR-PES. Further MEIS analysis using focusing∕blocking effect clearly shows that the Si adatoms take a $H$ site. The surface structure predicted by the ab initio molecular dynamics calculation coincides with the above structure model except for slight lateral displacements of the Si adlayer and reproduces well the present experimental results of MEIS and SR-PES.