In situ observation of nucleation by optical emission spectra in CVD diamond

Optical emission spectroscopy (OES) was used to in situ detect the intensity variation of C2 radical with the deposition time in the boundary layer during homo-nucleation of CVD diamond by DC Arcjet Plasma. The obvious drop and fluctuation of the optical emission intensity were found during the early growth stage. The samples grown after selected deposition time were characterized by micro-structural probes (transmission electron microscope (TEM), high resolution electronic microscope (HREM), selected area diffraction (SAD) and electron energy loss spectra (EELS)), in order to determine the occurrence of the diamond nucleation. Based on the results of the OES and the micro-structural probes, it was revealed that the variation of the optical emission intensity corresponded to the diamond nucleation. The incubation period and the lasting time of nucleation were thus deduced as 6–8 min and 20–60 s depending on the concentration of CH4 in H2. The incubation period decreased and the lasting time of nucleation increased with the increase of the concentration of CH4 in H2.