INFLUENCE OF METHANE CONCENTRATION ON THE NUCLEATION AND GROWTH-STAGES IN DIAMOND FILM DEPOSITION

Optical emission spectroscopy (OES) and mass spectrometry have been us ed to characterize the reaction species during the CVD synthesis of di amond films using methane and hydrogen gas mixtures in a microwave dis charge. In tile low methane concentration range, an increase in the nu cleation rate with the methane content in the reactor has been detecte d by scanning tunneling microscopy (STM), which has been associated to the increase in the atomic hydrogen as well as to the presence of CHx (x < 3) radicals, considered as precursors of amorphous and diamond-l ike carbon films. Although the further growth of the diamond films is mainly associated with CH3 radicals and/or C2H2 molecules, present in the discharge, other ionized CH+ species have been detected by OES, wh ich are known to favor the attachment of methyl radicals on the growin g surface.