Preparation of a colloidal crystal at a wall characterized with AFM

We present a new procedure to prepare high-quality colloidal crystals at a flat wall, which was oriented vertically in a colloidal suspension. The met hod is based on the depletion-induced effective attraction between the coll oidal particles themselves and between the colloidal particles and a flat w all. The concentrations of the colloidal particles and the depletion agents (polymers in this case) were chosen in such a way that phase transition oc curred not only at the wall but also in the bulk. In this way, good conditi ons were obtained to form high-quality colloidal crystals, consisting of se veral layers, at a flat wall in a relatively short time period. The crystal s formed were characterized with atomic force microscopy.