DIMER-ROW CORRELATIONS ON A SI(001) SURFACE WITH DOUBLE-ATOMIC-HEIGHT STEPS

The surface structure of a 4°-vicinal Si(001) sample tilted toward the [110] direction has been studied with low-energy electron diffraction. The correlation of dimer rows across double-atomic-height steps has been investigated by analyzing angular profiles of the diffracted beams. An irreversible phase transition has been discovered by observing the change of the splitting distances in individual (2×1) beams after heating the sample to above 1320°C. This change is considered as a result of converting a surface consisting of regions of terraces with dimer-row shifts all in the same direction from one terrace to the next within each region to a surface containing only single-direction dimer-row shifts for the entire surface. The phase transition is explained by the reduction of surface-stress-induced strain energy of the new phase. © 1994 The American Physical Society.