It was noted that the grain morphology of Si0.7Ge0.3 depended upon the number of primary non-coplanar twin variants which formed in the early stages of solid-phase crystallization. A grain, with major twin bands of a single twin variant parallel to a {111} plane, thus developed an elongated shape; due to preferential growth in a <112> direction along twins. When the grain had major twin bands of 2 or more non-coplanar twin variants, the growth front between non-coplanar twin bands developed just as fast as the <112> direction along twins propagated; because such a growth front was formed from a {111} ledge. As a result, the grain became more or less equiaxed due to the increasing number of primary non-coplanar twin variants.

Effect of twinning on the grain shape of crystallized amorphous Si0.7Ge0.3 thin films on SiO2 H.S.Kim, J.Y.Lee: Applied Physics Letters, 1998, 73[19], 2739-41