Thiolate-induced surface reconstruction of Cu(1 0 0) electrodes studied by in situ Video-STM

In situ Video STM was employed to study the formation mechanism and dynamics of the Cu checkerboard surface reconstruction induced by small coverages of adsorbed methyl thiolate on Cu(1 0 0) electrodes in 0.01 M HCl solution. The reconstruction process commences at potentials ⩽−0.60 V versus SCE by the formation of anti-phase shifted rows in the c(2 × 2) lattice of the chloride/thiolate coadsorbate layer, which are attributed to thiolates embedded into the Cu surface layer. These rows form a dense 2D network on the surface that exhibits pronounced fluctuations on the subsecond timescale, resulting in a highly disordered c(2 × 2) phase. This intermediate structure is replaced on time scales of minutes by the checkerboard reconstruction, in which the surface is covered by Cu adislands, consisting of small mobile islands of a slightly expanded c(2 × 2) structure. The dynamic observations support a stabilization of these adislands by thiolate, attached to the islands steps.