One-dimensional defects in iodine adlayers on Pt(1 0 0)

One-dimensional defect structures of closed-packed ( 2 × 5 2 ) R 45 ° adlayers of iodine on Pt(1 0 0) were studied with scanning tunneling microscopy (STM). On the terraces of the Pt(1 0 0) surface we observed rotational ( 2 × 5 2 ) R 45 ° domains with line defects running in [0 1 0] directions, in coexistence with nearly defect-free domains. In addition to these prevailing line defects (A-defects) with a local coverage lower than that of a defect-free surface, we report on much less frequently observed line defects with higher local coverages (B- and C-defects). The strong dependence of the concentration of these defects on the adsorption temperature is governed by the decrease of the overall iodine coverage with increasing temperature. Iodine adsorption at ∼1100 K leads to self-organization of A-defects in quasi-periodic arrangements. The relevance of these defects as important structural elements of commensurate ( 2 × n 2 ) R 45 ° superstructures of iodine on Pt(1 0 0) is stressed.