Twin formation and growth mechanism of tabular silver halide crystals

In this study the growth mechanism of {111} tabular silver halide crystals will be examined. The side-face structure and aspect ratio of tabular silve r bromide crystals grown from different concentrations of silver bromide di ssolved in dimethylsulphoxide (DMSO) were established in situ and ex situ. For tabular silver bromide crystals grown by the industrial double-jet prec ipitation method. transmission electron microscopy images of ultramicrotome d sections or the side faces were analysed. Also for tabular silver bromide and tabular silver chloride crystals grown from the vapour phase the relat ion between the aspect ratio and side-face structure was studied. Using the result of the different crystallization techniques it is shown that there is a strong relation between the aspect ratio and the side-face structure. For tabular crystals grown from DMSO. by industrial double-jet precipitatio n and from the vapour phase the san-ie relation between the aspect ratio an d side-face structure is observed. This provides evidence to support the id ea that the growth mechanism of {111} tabular crystals is universal and ind ependent of the crystal growth technique or crystallization medium. The pre ferential lateral growth of the tabular crystals can be explained by the su bstep mechanism proposed by Ming and co-workers in an earlier study. This m echanism explains the increase in growth rate of a {111} side face linked v ia a twin plane to a faster growing {100} side face.