Abstract
We have studied the atomic structure of up to one monolayer of Te on Si(001) using first-principles total-energy calculations. A low amount of Te atoms deposited on Si(001) is adsorbed on top of symmetric Si dimers. This configuration is preferred to adsorption on cave sites between Si dimers. For the one-monolayer coverage the most favorable structure corresponds to adsorption of Te atoms on near bridge sites. The $(1\ifmmode\times\else\texttimes\fi{}1)$ symmetry is broken by a small shift of Te atoms from perfect bridge positions, giving rise to a slightly disordered surface. This is a way to relieve the strain due to the size difference between Te and Si atoms. Missing Te rows is another way, and it is the one observed experimentally. We have calculated the atomic structure of the surface when one out of every five Te rows is missing. Two possibilities were examined. The most favorable corresponds to missing Te rows orthogonal to original Si rows. In all cases, our results are in good agreement with experimental data.
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