A channel for dimer flipping on the Si(001) surface

A mechanism of dimer flipping on the Si(001) surface has been investigated by means of ab initio pseudopotential calculations. These studies clearly demonstrate a tied flipping behavior of two consecutive dimers: the buckling of adjacent outer dimers becomes stronger while two inner dimers switch their orientation, which facilitates the inner dimer flipping by relieving the sublayer strain. Contrary to popular speculation, in most cases, the dimers undergo thermal fluctuations between two unequal energy minima. Hence, a clean Si(001) surface can preserve the 2 x anticorrelation of dimer buckling along a row at room temperature. (C) 2000 Elsevier Science B.V. All rights reserved.