Fig. 3. Pb₄S₃Cl₂/CsPbCl₃ epitaxial heterostructures.

a On the left, models of the Cs₂PbX₄-like Pb²⁺ subnetwork (orange Pb²⁺) and of the CsPb₂X₅-like [Pb₂S₃Cl₂]⁻ polyanion (white Pb²⁺, yellow S^2-, green Cl⁻) found in Pb₄S₃Cl₂. On the right, model of the Pb₄S₃Cl₂/CsPbCl₃ epitaxial interface superimposed on a close-up view of c, highlighting the continuity of the Pb²⁺/Cs⁺ cationic subnetwork. The Pb₄S₃Cl₂ structure has been represented by adapting the Pb₄S₃Br₂ structure. Atoms color code: Cs = cyan; Pb = orange/white; S = yellow; Cl = green. b Low resolution TEM image of as-synthesized Pb₄S₃Cl₂/CsPbCl₃ heterostructures. c HAADF-STEM image of a single Pb₄S₃Cl₂/CsPbCl₃ heterostructure. Insets: FFTs of the Pb₄S₃Cl₂ (top) and CsPbCl₃ (bottom) domains. The spots circled in a solid line correspond to planes parallel to the heterostructure interface and to each other; those circled in a dashed line are instead perpendicular to the interface and share similar periodicities, ensuring the match of the two lattices. d Column intensity map of the Pb-containing columns in the perovskite phase and of the Pb columns in the Cs₂PbX₄-like subnetwork of the Pb₄S₃Cl₂ domain. The color in the intensity map correlates with the total intensity scattered from the corresponding atomic column (red = higher intensity; blue = lower intensity). The map is compatible with the interface model depicted in Fig. 3a, and highlights the preservation and merging of the cationic subnetwork of the two phases across the interface. Source data for d are provided as a Source Data file.