In situ atomic force microscopy investigation of the growth of secondary nuclei produced by contact of different growth faces of potash alum crystalsunder supersaturated solutions

Contact of a potash alum crystal in a supersaturated solution with a solid surface may easily produce many secondary nuclei of the same orientation an d crystal structure as the parent crystal contact faces. Previous studies h ave shown that, if this contact is sufficiently gentle, secondary nuclei ma y be produced by the transfer of ordered solute molecules without the need for microabrasion of the parent solid. In this investigation, crystal faces of the {1 0 0}, {1 1 0}, and {1 1 1} families were identified in a parent crystal, and gentle contact between these and a solid surface (glass slide) in a slightly supersaturated solution of potash alum produced many seconda ry nuclei, the external symmetry of which reflected that of the parent face . In situ atomic force microscopy (AFM) measurements were carried out to st udy the early stages of the growth of these new nuclei. A strong correlatio n was found between the symmetry of the nuclei produced and that of the par ent crystal face. The topographies of the in situ growth of the (I 1 1) fac e of the parent crystal and those of the very small new nuclei produced wer e compared. (C) 1999 Elsevier Science B.V. All rights reserved.