Figure 3.

(a,b) HAADF-STEM image (a) and corresponding elemental mapping (b) of Cu_2–xS/ZnS HNCs. (c) Elemental line scan of a single Cu_2–xS/ZnS HNC (atomic ratios: Zn/S = 1.1 ± 0.4; Cu/S = 1.7 ± 0.4). The blue arrow in the lower panel indicates the scanned line. Elemental quantification was performed on 100 spots along this line. (d) HRTEM image of a single Cu_2–xS/ZnS HNC. A yellow arrow indicates the heterointerface between Cu_2–xS (red dashed contour line) and ZnS (blue dashed contour line). Scale bar is 5 nm. (e) FT patterns of Cu_2–xS part (upper panel) and ZnS part (lower panel). The FT patterns can be indexed to the axial projection of the high-chalcocite Cu₂S and the wurtzite ZnS structures along the [001] direction, respectively. (f) Schematic model for the atomic arrangement of the epitaxial growth of hexagonal wurtzite ZnS onto the (100) plane of hexagonal high-chalcocite Cu₂S through its (100) plane, viewed along the [001] direction. The atomic models of the (100) plane of Cu₂S and the (100) plane of ZnS are displayed on the right side. (g) Reconstructed 3D model of a single Cu_2–xS/ZnS HNC displaying a pronounced inter-NC contrast difference, similar to those in the lower left side of panel (a) [not the same HNC shown in panel (d)]. Images 2 and 3 correspond to image 1 rotated by 90 and 180°, respectively. Cu_2–xS is represented in cyan, while blue represents ZnS. An animated (rotating) version of this model is provided in the Supporting Information.