Authors: K. Okada
Affilation: National Institute for Materials Science, Japan
Pages: 4 - 7
Keywords: nanocrystalline diamond, low pressure inductively coupled plasma, sp2/sp3 chemical mapping
A 13.56 MHz low pressure inductively coupled CH4/CO/H2 plasma has been applied to prepare nanocrystalline diamond particles of 200-700 nm diameter. The minimum diameter of the particles was found to be 5 nm. Two-dimensional platelet-like graphite and carbon nanotubes also were deposited with different conditions. The TEM observations reveal that the two-dimensional platelet-like deposits consist of disordered microcrystalline graphite, whereas the particles are composed of only diamond nanocrystallites. The high-resolution TEM images clearly show that each particle is composed of small particles of about several ten nm in diameter. The electron energy loss spectrum (EELS) shows a peak at 290 eV due to (sigma)* states and the energy loss near edge structure is similar to that of diamond. A slight peak appears around 285 eV corresponding to (pai)* states. The mapping of sp2 states by (pai)* peak reveals that sp2-bonded carbons are localized in the grain boundaries of 20-50 nm sub-grains of nanocrystalline diamond particles at approximately 1 nm width. The low loss region of EELS exhibits a bulk plasmon peak of diamond at 33 eV and a surface plasmon peak of diamond at 23 eV. The diamond particles of 5 nm in diameter are expected to exhibit an emission in UV region and could be used for an UV-light emitting nanodevice.