Local phonon properties near heterointerfaces or lattice defects are key for controlling various material properties such as thermal conductivity and thermoelectricity. However, high-spatial-resolution measurements of bulk phonons have hardly been established, even in typical nonpolar and polar bulk materials such as diamond and cubic boron nitride (c-BN), respectively. Here, we demonstrate nanometric measurements of phonon dispersions and mapping using a heterojunction of diamond and c-BN single crystals. To achieve high spatial/energy resolution, we use a monochromated (∼20–30 meV) electron nanoprobe, a high-sensitivity scintillator for counting inelastically scattered electrons, and the Richardson–Lucy deconvolution. The diamond phonon dispersion is first measured under a large-scattering-vector condition, particularly for the Γ point. Differential scattering cross sections of optical and acoustic-phonon modes in diamond and c-BN are also measured, and the totals of their modes are on the order of ${10}^{-5}\mathrm{n}{\mathrm{m}}^2$ for both crystals.

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• Phonons
• Diamond
• Nitrides
• Electron energy loss spectroscopy
• Scanning transmission electron microscopy