Detection of Acoustic Phonons in Carbon by Raman Spectroscopy

We detected acoustic phonons in graphite and diamond by Raman spectroscopy supported by density functional theory calculations. The activation of these normally forbidden Raman modes was achieved via lattice amorphization in the case of graphite and by boron doping in the case of diamond. The doping‐induced Raman signal in diamond was identified with substitutional boron of tetrahedral symmetry via its dependences on excitation wavelength and polarization. Comparison of the Raman spectra of amorphized graphite and heavily boron‐doped diamond suggests the emergence of graphitic‐like disorder in the diamond lattice. The reported approach is not limited to carbon and can be extended to a wide range of other materials.