Surface decoration: Localization of crystallites along the steps

The interest of decorating surfaces by metallic particles is to point out defects and in particular, steps. However, the precise localization of these particles is not known. It is shown here, by statistical measurements, that gold and palladium nuclei settle in the upper part of diatomic and monoatomic steps of (100) KCl. This unexpected localization is interpreted by the consideration of the elastic strain field, induced in the substrate by an in-contact crystallite. A crystallite placed near to the lower part of a step finds itself in a repulsive situation. When localized in the upper part, an attractive force counterbalanced by the line tension of the step exists. It is understood that decorating crystallites moving along the steps do not leave them, as it has been revealed by measurements and observations.