The role of {1 0 0} side faces for lateral growth of tabular silver bromide crystals

Abstract

In this study the growth of {1 1 1} tabular silver bromide crystals will be examined in situ under different conditions to determine a general growth mechanism. We established the side-face structure and aspect ratio of the tabular crystals for different concentrations of silver bromide dissolved in DMSO during the growth. The morphology of non-twinned crystals was studied to examine the relative growth rate of the {1 0 0} faces as compared to the {1 1 1} faces. It will be shown that there is a strong dependency between the relative growth rate of the {1 0 0} faces and the aspect ratio and side-face structures of the {1 1 1} tabular crystals. Relative fast growth of the {1 0 0} faces in comparison to the {1 1 1} faces leads to high aspect ratios and side-face structures with acute edges built up by {1 1 1} side faces. Relative slower growth leads to lower aspect ratios and ridge side-face structures built up by stable {1 1 1} and {1 0 0} faces. The lateral growth for all conditions can be explained by the substep mechanism proposed in an earlier study. This mechanism explains the increase of growth rate of a {1 1 1} side face that is linked via a twin plane to a faster growing {1 0 0} side face. From this mechanism and the observations it will be shown that the faces between the twin planes for double-twinned tabular crystals can be determined. The results presented here are not only valid for tabular crystals grown in the DMSO system but also for tabular crystals grown from the vapour phase and in the industrial precipitation method.