Polarity and inversion twins in ZnSe crystals observed by high-resolution electron microscopy

Zinc selenide crystals (zinc-blende structure) with (110) surface planes, produced by a solid–solid reaction, have been examined by means of a multi-beam lattice-imaging technique in a 200 kV electron microscope with a pole piece of C s = 1·2 mm, and by simulaton using the multi-slice method. In the experimental images the columns of Zn and fie atoms have been positoned so that the crystallographic polarity, as well as the stacking sequence, can be determined. Inversion twins, the components of which have opposite senses of polar axes across the boundary, have been found parallel to (111). It is concluded that the lattice on one side of the twin boundary is displaced from that on the other side by α/8[110] and that the formal charge at the two types of (111) boundary, positive and negative, is compensated by removing or supplying Zn atoms. It has been observed that layers with a wurtzite-type stacking sequence ere also formed by the introduction of similar growth stacking defects.