Effect of excessive amount of Cd(II) cations on surface morphology of prismatic {110} faces of cadmium mercury thiocyanate crystals

Surface morphologies of cadmium mercury thiocyanate crystals grown from synthesized mother solutions with excessive amount of Cd(II) cations (5%, 20% and 50% in molar ratio) are investigated by atomic force microscopy. Unlike our previous observations, strong anisotropic growths occur at the large two-dimensional nuclei as well as at steps generated by 2D nuclei. These steps are highly bunched macrosteps varying from 1.6 up to 35 nm in height with distinctly well-oriented protuberance trains at the step fronts while regular elementary steps are hardly observed. These protuberances, however, become fewer and less distinct with the increase of excessive Cd(II) cations in the solution and even disappear at a much higher concentration of 50%. Steps also vary from macrosteps to dominant substeps with the height of 1 and 2 elementary steps of 0.81 nm at this high concentration. These distinct surface morphological variations are assumed to result from the effect of Cd–SCN complex anions as either growth units or impurities under different growth conditions. r 2002 Elsevier Science B.V. All rights reserved.