The behavior of steps and out-of-phase boundaries of the 7 x 7 reconstruction on the (111) surface during Si molecular beam epitaxy was reported. During step-flow growth, the Si atoms were preferentially incorporated into the crystal at positions where steps were connected with out-of-phase boundaries on the lower terraces; resulting in sawtooth-shaped steps. This heterogeneous advance of the steps caused the out-of-phase boundaries to rearrange, and thereby decrease in number.

H.Hibino, T.Ogino: Applied Physics Letters, 1995, 67[7], 915-7