Self-organised periodic surface structures are prepared by spinodal decomposition of AgCl-NaCl single crystals and subsequent ex-solution of the alkali-rich component. While the kinetics of decomposition was studied previously by time-resolved neutron scattering, in the present paper, the etching process is studied in some detail and the surface structures are characterised by atomic force microscopy. It is shown that the duration of both, the demixing process as well as the etching process, determines the characteristic length scale of the periodic pattern. Under well controlled conditions, relief structures with wavelengths of some 100 mn are obtained that are uniform over areas of some mm(2). These patterns can possibly be used as templates for the decoration with metals, macromolecules, etc. (c) 2006 Elsevier B.V All rights reserved.