Atomic force microscopic studies of stabilization of NaCl(1 1 3), (1 1 2) and (1 1 0) surfaces in ethanol, CdCl2/ethanol and HgCl2/ethanol

Facet formation processes at various crystal faces of NaCl were observed with atomic force microscopy (AFM) to study the mechanisms of stabilization of the surfaces with additives in solutions. The most stable surfaces in respective conditions gave atom-resolved AFM images. In ethanol, the most stable face is (1 1 3), where ethanol molecules presumably adsorb at {1 1 1} ledges of Na ions along the 〈1 1 0〉 direction. The atom-flatness was kept in the air. In ethanol solution of CdCl2 (0.01 mol dm−3), (1 1 2) surface is the most stable. When the sample was taken out of the solution, a line pattern along the 〈1 1 0〉 direction was imaged with AFM. This is attributable to a chain structure of Cd-chloro complexes formed at {1 1 1} ledges. In ethanol solution of HgCl2 (0.05 mol dm−3), (1 1 0) face became atom-flat, giving atom-resolved AFM image in air. The (1 0 0) surface, and the monatomic {1 1 1} ledges on it were stable, too. The (1 1 3) faces having repeated (1 1 1) ledges were also fairly stable in the solution. Models were proposed to explain the stableness of the surface structures by the formation of octahedral Hg-chloro complexes.