Homogeneous synthesis of nanodiamond grains in low-pressure plasmas
L. Vandenbulcke, T. Gries, J.N. Rouzaud, S. de Persis
ICARE - CNRS, FR
Keywords: Nanodiamonds, low-pressure plasma, plasma diagnostics, modeling, transmission electron microscopy
Abstract:The homogeneous synthesis of nanodiamond grains (10-100 nm in size) made of either pure diamond nanocrystals only (2-10 nm in size) or mixed with some sp2-carbon entities have been studied experimentally and by 2-D modeling of the kinetics/hydrodynamics of the plasma. Kinetic description of non-dusty CH4-CO2 plasmas was validated by comparing the predicted species concentrations to the results obtained by molecular beam mass spectrometry (MBMS). It has been extrapolated to dusty plasmas where no MBMS measurements could be carried out. The influence of heavy gaseous species and the influence of electron energy change in dusty plasma conditions on the nucleation process are emphasized. These studies allow a better understanding of the homogeneous nucleation and a better control of the size and the nanostructure of nanodiamond grains. These nanodiamond grains can be composed of pure diamond nanocrystals only, they can be surrounded by sp2-hybridized carbon shells or they can incorporate sp2-carbons between the diamond nanocrystals. The control of their size and their nanostructure could open ways for applications in various scientific fields when used either as-synthesized or after various post-treatments to increase their porosity and/or to permit their functionalization.