The first low-temperature scanning tunnelling microscopic images of Si(001) were presented. It was observed that, upon cooling to 120K, the number of buckled dimers increased; confirming that the dimers had an asymmetrical nature. Buckled-dimer domains of c(4 x 2) order were bounded by p(2 x 2) regions. Defects pinned nearby dimers into a buckled configuration and acted so as to smear out the transition to order. At room temperature, dimers rapidly switched orientation; leading to an averaged symmetrical appearance in scanning tunnelling microscopic images.

Direct Observation of an Increase in Buckled Dimers on Si(001) at Low Temperature. R.A.Wolkow: Physical Review Letters, 1992, 68, 2636-9