用会聚束电子衍射对SiC中多型鉴定

IDENTIFICATION OF POLYTYPES IN SiC WITH CONVERGENT BEAM-ELECTRON DIFFRACTION TECHNIQUE

本文根据会聚束电子衍射基本原理,利用CBED花样中的HOLZ环半径对SiC中多型进行鉴定。其中包括最常见的4H、6H和45R多型。同时用该方法测定了具有较高层数的180R多型。该方法根据CBED花样的对称性,可准确测定SiC中多型所属的(H或R)结构类型,从而避免了在对较高层多型nH和3nR区别时,结构因子的复杂计算。

Four polytypes in SiC have been identified with convergent beam electron diffraction (CBED) technique in this paper, including the most common 4H, 6H and 45R and a new-type-180R. The principle is based on the relationship between the radius (G) of HOLZ and the distance (H) of reciprocal lattice vertical to the direction of [uvw] zone: H=λ/2G^2. The first type of lattices is confirmed easily from the symmetry of the CBED patterns. Then, the number of layers in the polytype can be calculated from the measured G values. The use of this method can avoid complicated calculation for structure factors when the polytypes with greater number of layers are distinguished between nH and 3nR.