Fig. 1: Isotope identification of h−¹⁰BN/h−¹¹BN interface.

a Schematic of the assembled stack of h-¹⁰BN, h-¹¹BN, and Si substrate with amorphous SiO₂ (a-SiO₂) layer on surface. b HAADF image of the h-¹⁰BN/h-¹¹BN/a-SiO₂ cross-section. c STEM-EELS vibrational spectra were acquired at the region of the orange rectangle labeled in b. The vibrational signals from the h-BN in-plane direction, a-SiO₂ and h-BN out-of-plane direction are labeled by green, white and blue dashed rectangles, separately. d STEM-EELS vibrational spectra. The red, purple, and blue solid lines are acquired from h-¹⁰BN, interface, and h-¹¹BN, separately. The details of acquisitions and processing procedures are included in methods. e Energy-filtered images of h-¹⁰BN/h-¹¹BN. The acquisition region is labeled by the white rectangle in b, and the energy selection windows are shown as vertical shades in d and labeled on the left-up corner of each map.