Systematic error in conventionally measured Raman spectra of boron carbide-A general issue in solid state Raman...

Solid state Raman spectroscopy requires careful attention to the penetration depth of exciting laser radiation. In cases like semiconducting boron carbide and metallic hexaborides, high fundamental absorption above the bandgap and reflectivity R ≈ 1 beyond the plasma edge respectively prevent the excitation of bulk phonons largely. Thus, correspondingly measured spectra stem preferably from surface scattering. For decades, Raman spectra of boron carbide obtained with different equipment were controversially discussed. Now, common features of icosahedral phonons in Fourier transform-Raman spectra of B_4.3C and Raman spectra of α-rhombohedral boron evidence their bulk character, while refuting conventionally measured Raman spectra.