THE ROLE OF (100)SIDE FACES FOR LATERAL GROWTH OF TABULAR SILVER BROMIDE CRYSTALS

In this study the growth of {1 1 1} tabular silver bromide crystals wi ll be examined in situ under different conditions to determine a gener al 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-twi nned 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 t here 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 comp arison 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 s lower growth leads to lower aspect ratios and ridge side-face structur es built up by stable {1 1 1} and {1 0 0} faces. The lateral growth fo r 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 gr owing {1 0 0} side face. From this mechanism and the observations it w ill be shown that the faces between the twin planes for double-twinned tabular crystals can be determined. The results presented here are no t only valid for tabular crystals grown in the DMSO system but also fo r tabular crystals grown from the vapour phase and in the industrial p recipitation method. (C) 1998 Elsevier Science B.V. All rights reserve d.