Ge-induced surface reconstructions on the 4° vicinal Si(100) surface

We report results of a combined study of low-energy-electron diffraction (LEED) and Monte Carlo simulations for the Ge-adsorbed single-domain stepped Si(100) surface. The (4 x I)structure, least favored energetically among the (2 x 1) family of the dimer-induced structures, is found to appear on the Ge-adsorbed Si(001) surface in a limited range of temperatures slightly below room temperature. With mild annealing at similar to 370 K, the surface undergoes irreversible transitions initially to a (3 x 1)and then ultimately to a (2 x 1) structure after prolonged annealing. We propose that the (4 x 1) structure consists of an antiferromagnetic arrangement of A-type Ge ad-dimers, which decompose and recombine into C-type ad-dimers for the high-temperature structures upon annealing. In addition, results of Monte Carlo simulations suggest that the (4 x 1) surface is the most stable structure when the signs of the Ge inter-dimer interaction parameters are exactly opposite to those of the c(4 x 2) + p(2 x 1) surface. (C) 1999 Published by Elsevier Science Ltd. All rights reserved.