First-principles pseudopotential calculations were made of the geometrical structures of Ge, Si and mixed Si-Ge dimers on the Si(001)-(1 x 2), Si(001)-(2 x 2), Ge(001)-(1 x 2) and Ge(001)-(2 x 2) surfaces. The results showed that there was a clear energy gain in going from the (1 x 2) reconstruction to a semi-antiphase (2 x 2) reconstruction, for all of the systems. For the above reconstruction change, significant elongation was found to occur for pure Ge-Ge and mixed Si-Ge dimers, but not for pure Si-Si dimers; in spite of a similarly beneficial change in substrate relaxation.

Dimer Length Variation for Different Reconstructions of Si, Ge, and mixed Si-Ge Dimers on Si(001) and Ge(001) Substrates S.C.A.Gay, G.P.Srivastava: Physical Review B, 1999, 60[3], 1488-91