Effects of hydrogen additive on microwave plasma CVD of nanocrystalline diamond in mixtures of argon and methane

Nanocrystalline diamond films were deposited on silicon by microwave plasmas in gas mixtures of 1%CH₄ + 99%Ar and 1%CH₄ + 5%H₂ + 94%Ar. Plasma compositions, Raman scattering, average surface roughness, surface morphology and electron field emission characteristics were examined and correlated. Without the addition of hydrogen, smoother nanodiamond films were grown. However, the hydrogen additive stabilized the plasma and reduced the deposition of carbon clusters on nanodiamond films. Nanodiamond films deposited at a gas pressure of 200 Torr without hydrogen additive were found to emit a higher electron current than other specimens deposited at lower gas pressures or deposited in plasmas with hydrogen additive. Surface roughness including micron and sub-micron sized particles on the surfaces of the nanodiamond films were believed to at least partially contribute to the difference in electron field emission current among tested nanodiamond films.