Fig. 2
From: Interfaces between hexagonal and cubic oxides and their structure alternatives
Orientation relationship for c-ZnO. Cross-section scanning transmission electron microscopy (STEM)-high-angle annual dark-field (HAADF) images of (a) c-ZnO-I and (b) c-ZnO-II domains of polar film. Scale bar, 2 nm. The beam is parallel to the [110]MgO direction. The high contrast dots on the left correspond to Zn atoms, while weak contrast dots in the right correspond to Mg atoms. The O atom is invisible due to its low atomic number. The insets show the magnified images from the area outlined by the yellow rectangles with the atomic projection of [100]cZnO-I in (a) and [−1−20]cZnO-II in (b) embedded (red: Zn, green: Oepi, yellow: Osub, blue: Mg). [100]cZnO-I is aligned with [110]MgO, showing centered-rectangle atomic arrangement. The c-ZnO-II is rotated 90° along [001] direction in terms of ZnO-I and viewed along [−1−20]cZnO-II, showing close-packed rectangular atomic arrangement. The two yellow dashed arrows in a indicate the alignment of a ZnO row with respect to an MgO row. c Projection of the interface for c-ZnO-I along [100] direction (upper panel) and c-ZnO-II along [−1−20] direction (lower panel) derived from STEM images. d Top view (one layer of (001)ZnO plane on top of one layer of (001)MgO plane) of the interface, which is the interface area outlined by the brown rectangle in c (rotated 90° clockwise). The unit cell of the c-ZnO-II domain (outlined by green parallelogram) is rotated 90° from that of the c-ZnO-I domain outlined by red parallelogram
