Extended Data Fig. 5: Structural and elemental characterization of the Si/hBN heterostructure interface.

(a) Cross-sectional high-resolution TEM image of the Si/hBN interface, demonstrating sharp atomic alignment. Scale bar: 50 nm. (b) Magnified lattice-resolved view of hBN layers marked in (a). High-angle annular dark-field (HAADF) STEM image confirming uniform hBN layer thickness (~1.7 nm) and continuity across the Si substrate. Scale bar: 5 nm. (c) Composite electron energy-loss spectroscopy (EELS) elemental map showing boron (B, purple), nitrogen (N, red), oxygen (O, blue), and silicon (Si, green) at the interface. (d) Corresponding intensity line profiles of B, N, O, and Si across the dashed line in (c), revealing minimal elemental intermixing and a sharp chemically interface. (e–h) Individual EELS elemental maps for B, N, O, and Si, spatially resolved at the heterojunction. (i–l) Element-specific intensity line profiles derived from (e–h), quantifying the distribution of each element. Profiles confirm negligible oxygen diffusion and sharp Si/hBN interfacial boundaries. All data were acquired using a probe-corrected Titan Themis Z TEM operated at 200 kV. Scale bars for elemental maps: 10 nm. Error margins for line profiles reflect a 5% signal-to-noise ratio.