Résumé
I will discuss here our recent results in isotopically-purified hBN crystals. We combined Raman scattering, photoluminescence, and X-ray diffraction for an in-depth characterization. On the one hand, as with standard semiconductors, both the phonon energy and electronic bandgap varied with the boron isotope mass, the latter due to the quantum effect of zero-point renormalization. On the other hand, temperature-dependent experiments focusing on the shear and breathing motions of adjacent layers revealed the specificity of isotope engineering in a layered material, with a modification of the Van der Waals interactions upon isotope purification.