Metal Adlayer-Induced Relaxation of Au(111) Reconstruction under Electrochemical Control

摘要

Underpotential deposition of Sb has been observed to induce a relaxation of Au(111)(√3 * 22) reconstruction to corrugation lines of trigonal networks. The triangles typically appear pairwise with an average length of the baselines of ～20.2 ± 1.0 nm and a height of the triangles of ～10.6 ± 1.4 nm at a corrugation height of ～0.05 nm. The baselines of the trigonal network rotate by 30° with respect to the corresponding double rows of the (√3 * 22) reconstruction and align along one of the three {110} directions. An atomic resolution image reveals an apparent (√3 * √3) structure in the regions with hcp stacking sites enclosed by the triangles, which is attributed to the atomically dispersed surface alloy structure of Sb with the topmost Au atoms. Similar relaxation structures are observed with decreasing coverage via irreversible adsorption, although the size of the relaxation is alleviated. The surface alloying is confirmed by the creation of holes upon anodic stripping, the holes being confined at the connections between the two triangles. The results are rationalized as a consequence of compromise between two opposing effects: directional bonding via electron back donation, which tends to lift the reconstruction, and dislocation-mediated alloying, which favors the formation of relaxed reconstruction. The present study provides a good link with the studies in UHV as well as further knowledge for a thorough understanding of (sub)monolayer deposition in electrochemical environments.