Determination of vibrational modes in electron energy loss spectroscopy of polycrystalline diamond surfaces by isotopic exchange

The high resolution electron energy loss spectrum of polycrystalline diamond films deposited from various isotopic gas mixtures, (CH4)-C-12+H-2, (CD4)-C-12+D-2, and (CH4)-C-13+H-2, are reported. Three types of peaks were unambiguously identified: (1) Pure C-C related peaks (a diamond C-C stretch at similar to 150 meV and its overtones at 300, 450, and 600 meV), (2) pure C-H related peaks (C-H bend at similar to 150 meV and C-H stretch of sp(3) carbon at 360 meV), and (3) coupling of C-H and C-C peaks (similar to 510 meV peak due to coupling of the C-H stretch at 360 meV with either the C-C stretch or the C-H bend at similar to 150-155 meV).