Twin Domains in 111 Oriented {CdO/MgO} Superlattices: Homoepitaxy Versus Heteroepitaxy

The structural properties of (111)‐oriented {CdO/MgO} superlattice (SL) structures grown on c ‐sapphire and cubic MgO substrates have been studied by high‐resolution X‐ray diffraction. The growth is performed in a plasma‐assisted molecular beam epitaxy system. Although both SLs are (111)‐oriented and the {CdO/MgO} structure has 3m symmetry. It is shown that the SL on c ‐sapphire consists of misoriented domains, whereas no such domains are observed on (111) MgO. The twin domains of {CdO/MgO} SLs are rotated by 180° with respect to each other. Additionally, the in‐plane [110] {CdO/MgO} SLs are turned around by ±30° with respect to the in‐plane [1–1.0] Al 2 O 3 substrate. It is shown that the crucial phenomena based on the formation of rotation domains and their number in heteroepitaxy depend fundamentally on the relationship between substrate and epilayer symmetries.