Figure 5

STM images of the clean Si(001) surface prepared in the slow-cooling mode: (a) the surface mainly covered by the (2 × 1) structure (+2.0 V, 100 pA), '1' and '3' are terraces; the height of the row '2' coincides with the height of the terrace '1'; (b) a magnified image taken with atomic resolution (-1.5 V, 150 pA), 'A' is the "rectangle", 'B' marks the dimer rows composing the (2 × 1) structure (separate atoms are seen), 'C' shows structural defects, i.e. the dimers of the uppermost layer oriented along the dimers of the lower (2 × 1) rows.