Origin of the 1150-cm-1 Raman mode in nanocrystalline diamond -: art. no. 121405

The peak near 1150 cm(-1) in the visible Raman spectra of poor quality chemical-vapor-deposited diamond is often used as the signature of nanocrystalline diamond. We argue that this peak should not be assigned to nanocrystalline diamond or other sp(3)-bonded phases. Its wave number disperses with excitation energy, its intensity decreases with increasing excitation energy, and it is always accompanied by another peak near 1450 cm(-1), which acts similarly. This behavior is that expected for sp(2)-bonded configurations, with their smaller band gap. The peaks an assigned to transpolyacetylene segments at grain boundaries and surfaces.