Extended Data Fig. 4: Nanoscale structural mapping of hBN via 4D-STEM.

(a) Schematic of the 4D-STEM selective area mapping technique, where a quasi-parallel electron probe (convergence angle: 0.5 mrad) is scanned across the TEM lamella, recording spatially resolved diffraction patterns recorded at each probe position. Scale bar: 10 nm. (b) High-resolution TEM (HRTEM) image of the selected hBN region, showing lattice fringes corresponding to the (002) basal plane spacing (~0.34 nm). Scale bar: 10 nm. (c) Atomic-resolution HAADF-STEM image of the same region from (b). Scale bar: 10 nm. (d, e) Representative nano-beam electron diffraction (NBED) patterns from two distinct hBN grains in the selected hBN region. The diffraction rings indicate a nanocrystalline structure. Reciprocal space scale: 5 nm⁻¹ (Q-space).