A multichannel-detection Raman microprobe, with laser-excitation at 514.5 nm, is employed in the rapid characterization of the microstructural and compositional perfection of diamond deposits prepared by the hot-filament chemical vapor deposition (CVD) method. Examined are single microcrystals of CVD diamond and polycrystalline thin diamond films deposited on silicon ((111) Si) and polycrystalline mullite (3Al₂O₃.2SiO₂) substrates. Reported are the results from a series of films grown under constant deposition conditions of substrate temperature (750 °C), gas pressure (40 torr), and gas flow rate (52 sccm), but employing varying gas compositions with CH₄:H₂ ratios of 0.1 to 1.0 percent. The analysis focuses on the Raman range from 800 to 2000 cm^-1 to establish the purity of the diamond phase based on the observation of characteristic carbon (i.e., sp³, sp², and sp bonding) signatures and the level of the spectral background. A second spectral range from 5600 to 6200 cm^-1 (Raman shift) is examined to monitor the presence of a photoluminescence (PL) band centered at 738 nm (1.68 eV) attributed to a lattice vacancy in diamond. The spectra characterizing the laser-excited optical emissions are correlated with the structure and morphology of these depositions established by several other characterization techniques. The conclusions drawn with respect to structural imperfections of the diamond phase are related to the deposition parameters employed and the resulting nucleation and growth processes involved.

Date Published: 15 January 1989
PDF: 15 pages
Proc. SPIE 1146, Diamond Optics II, (15 January 1989); doi: 10.1117/12.962067

Published in SPIE Proceedings Vol. 1146:
Diamond Optics II
Albert Feldman; Sandor Holly, Editor(s)