Use of lattice imaging in the electron microscope in the structure determination of the 126R polytype of SiC

Lattice fringes corresponding to (00.3) spacings of the 126R polytype of SiC have been obtained in the electron microscope. A number of 10.l reflections were allowed to pass through the objective aperture to obtain the lattice fringes showing a periodicity of ~ 105 Å (one third of the c parameter of the hexagonal cell) and each unit-cell block is subdivided into smaller blocks corresponding to the spacings of 6H, 15R, 21R etc. The stacking sequence of these blocks has been used to work out the detailed structure of the 126R polytype. It has been suggested that the lattice resolution technique in conjunction with X-ray diffraction is likely to prove a useful method for determining difficult polytypic structures.