Extended Data Fig. 1: Cross-sectional characterization of (BA)2PbBr4-(BA)2(MA)2Pb3I10 vertical heterostructure.
From: Layer-by-layer anionic diffusion in two-dimensional halide perovskite vertical heterostructures
a, SEM image of the vertical heterostructure (top view). The dashed rectangle highlights the area used for cross-sectional characterization. b, Carbon coating of the rectangular area of interest. Preparation of the cross-sectional lamella by c, digging a hole and d, thinning by Ga ions. e, Prepared cross-section of the vertical heterostructure. Scale bars in a–e are 10 µm. f, Low-magnification STEM image of the vertical heterostructure. The scale bar is 1 µm. g, Enlarged STEM image of the vertical heterostructure. STEM images show a clear interface between (BA)2PbBr4 and (BA)2(MA)2Pb3I10. EDS elemental mapping of h, Pb, i, Br, and j, I. k, Overlaid bromine and iodine EDS mapping. Scale bars in g–k are 200 nm. The brighter bromine and iodine signals in the EDS elemental mappings are mainly concentrated in the pure phase (BA)2PbBr4 and (BA)2(MA)2Pb3I10 regions, respectively. The dimmer Br signal from (BA)2(MA)2Pb3I10 region and iodine signal from (BA)2PbBr4 region can be attributed to diffusion, which is likely caused by the harsh sputtering and focused ion-beam milling during the cross-sectional sample preparation. These results suggest that electron microscopy is not an ideal tool to study the anion inter-diffusion kinetics for 2D halide perovskites due to sample damage.
