CVD Si₃N₄ on single crystal SiC: Part II. High resolution electron microscopy and atomic models of the interface

Interface studies of CVD Si₃N₄ grown on (11$\overline 1$) SiC single crystal substrates have been made by transmission electron microscopy (TEM). It is found that there are two orientation relationships both of which involve the same (10$\overline 1$0)Si₃N₄//(11$\overline 1$)SiC planar relationship. However, the orientation relationships are not perfect and rotations of 2–6° are commonly seen between both directions and planes involved. High resolution electron microscopy (HREM) of the interfaces shows that the SiC and Si₃N₄ are continuous up to the interface and that no intermediate phases are formed. However, due to the small rotations, the HREM images are difficult to interpret directly in terms of atomic positions. Nevertheless, possible atomic models of the interface are proposed based upon the experimental findings. These models exploit the similarities between the [SiN₄] and [SiC₄] tetrahedra in Si₃N₄ and SiC, respectively. The observed orientation relationships appear to be due to matching of tetrahedra across the interface along with adequate lattice matches.