Adsorption process, atomic geometry, electronic structure and stability ofSi(001)/Te surface

The adsorption process, atomic geometry, electronic structure and energetic s of a Si(001) surface covered by Te atoms have been studied using first-pr inciples total-energy calculations. Our findings indicate that the Te atoms adsorb in the 'bridge' site on the surface Si dimer bond, in agreement wit h recent experimental results. We have also verified that the Si dimers (un derneath adsorbed Te atoms) do not dissociate, The subsequent atomic exchan ge between the adsorbed Te atom and the surface Si atom, giving rise to an interdiffusion process of Te atoms towards Si substrate, is not an exotherm ic process. We have considered a number of possible coverages of Te atoms o n Si(001) surface and our results indicate that for a coverage of one monol ayer (1 ML). the Si(001)/Te-(1 x 1) surface represents the energetically mo re stable configuration. For a coverage of 2/3 hit, we have verified the fo rmation of Te-Si-Te mixed trimers, in a (3 x 1) reconstructed surface. At 1 /3 ML coverage, we have obtained the formation of Si dimers with a single T e atom at the surface, in a (3 x 1) reconstruction. Finally, for a coverage of 1/2 ML, we have obtained the formation of Si-Te mixed dimers, in a (2 x 1) reconstructed surface, but the calculated formation energy indicates th at this atomic configuration is not energetically favourable. (C) 2000 Else vier Science B.V. All rights reserved.