Structure of Pb dimer chains on Si(1 0 0)2×1

We have investigated the structure of Pb chains grown on the Si(1 0 0)2×1 surface by means of scanning tunnelling microscopy at variable temperature (50–300 K). We have observed the coexistence of both intrinsically symmetric and asymmetric dimers in the chains at low temperature. The analysis of the data suggests that this may arise from the interplay of a termination (end) effect and of a significant dimer–dimer interaction. In particular, “free” ends of the chains seem to impose the direction of buckling of neighbouring dimers.