Cross-sectional bright-field (BF) and dark-field (DF) transmission electron micrographs of Bi2Se3 sample BS-100 demonstrating the twin domain distribution in the film's cross section are shown in panels (a) and (b), respectively. The substrate/Bi2Se3 and Bi2Se3/Pt interfaces are indicated by white dashed lines. Diffraction contrast between the two twin orientations in BF imaging conditions is achieved by tilting the specimen to enhance the contribution of one domain (c). The DF was created using the () reflection where only one twin domain contributes. The limited vertical extent of a tilted twin domain is marked by a green arrow. Panel (c) shows the diffraction image of the imaging conditions with specimen orientation close to the  zone axis. Yellow and red colours indicate the reciprocal lattices of the two twin orientations in the thin film, while cyan marks that of the substrate.