Ab initio pseudopotential calculations for electronic and geometric structure of mixed Si-Ge dimers on the Si(001)-(1 x 2) and Si(001)-(2 x 4) surfaces

We report on ab initio pseudopotential calculations for electronic and geometric structure of mixed Si-Ge dimers on the Si(001)-(1 x 2) and Si(001)-(2 x 4) surfaces. The structural parameters obtained from our calculations provide some agreement with the recently proposed structure by Chen et al. based on adjacent substitutional Si-Ge dimers buckled in opposite directions. Dimer bonding and electronic states in the silicon band gap are also studied. It is noted that the c-(2 x 4) reconstruction provides a more efficient substrate relaxation mechanism than does the simple (1 x 2) reconstruction. (C) 1999 Elsevier Science B.V. All rights reserved.