Growth mechanism of twin-related and twin-free facet Si dendrites

The various types of facet Si dendrites observed on splat-quenched surfaces were analyzed in order to understand why the growth direction and morphology of the facet Si dendrites change with increasing undercooling. The growth directions of typical facet dendrites were determined to be (left angle bracket)2 1 1(right angle bracket) , (left angle bracket)1 1 0(right angle bracket) and (left angle bracket)1 0 0(right angle bracket) using an electron backscatter pattern apparatus. It was found that both the (left angle bracket)2 1 1(right angle bracket) and (left angle bracket)1 1 0(right angle bracket) dendrites with twins were bounded by atomically smooth {1 1 1} planes. Therefore, their growth is governed by the incorporation of atoms at re-entrant corners formed by twins. The (left angle bracket)1 0 0(right angle bracket) dendrites with fourfold symmetry have no twins and are commonly observed at high undercoolings. Moreover, two kinds of (left angle bracket)1 0 0(right angle bracket) dendrites with different secondary arm directions (left angle bracket)1 0 0(right angle bracket) and (left angle bracket)1 1 0(right angle bracket) were clarified for the first time. The dendrite tip shape and facet planes, as determined using an atomic force microscope, suggest that the (left angle bracket)1 0 0(right angle bracket) dendrites are bounded by atomically rough {1 1 0} and {1 0 0} planes. That is, facet Si dendrites vary in their growth direction and morphology with increasing undercooling because the dendrites select atomically rough interfaces in order to promote the incorporation of atoms at high undercoolings.