Sp 2 bonding distributions in nanocrystalline diamond particles by electron energy loss spectroscopy

Nanocrystalline diamond particles with 200–500 nm in diameter have been prepared in a 13.56 MHz low pressure inductively coupled CH4/CO/H2 plasma. The chemical bonding map was investigated by electron energy loss spectroscopy (EELS). The EEL spectrum shows a peak at 290 eV due to σ* states and the energy loss near-edge structure is similar to that of diamond. A slight peak appears at ∼285 eV corresponding to π* states. The mapping of sp2 states by π* peak reveals that sp2-bonded carbons are identified around the 20–50 nm subgrains of nanocrystalline diamond particles at approximately 1 nm resolution.