摘要
SiC is known to form many polytypes with different stackings of close-packed layers among which 4H, 15R, 6H and 21R are the polytypes most frequently occurring. Up to the present of the more than one hundred polytypes known many have been found belonging to the [（3, 3）n （3, 2）]8 and [（3, 3）n （3, 4）]8 families. They could be considered as structures derived from the （3, 3） stacking sequence of the 6H poly-
