Comparisons of HFCVD diamond nucleation and growth using different carbon sources

• MCD films are fabricated using different carbon sources by BE-HFCVD.
• Typical carbon sources used include methane, acetone, methanol and ethanol.
• The nucleation, growth and basic characteristics are compared.
• Methane can guarantee high film quality and low residual stress.
• Acetone can provide high growth rate and relatively high film quality.

The differences between the nucleation, growth and basic characteristics of bias-enhanced hot filament chemical vapor deposition (BE-HFCVD) microcrystalline diamond (MCD) films fabricated under the different carbon source (methane, acetone, methanol and ethanol) environments are studied in this article, adopting SiC chips as substrates. With the same commonly-used nucleation parameters, acetone and ethanol can provide either higher nucleation density (ND) or larger nuclei size (NS). Besides, under the same commonly-used growth conditions, relatively higher growth rate (R) of the MCD film is obtained adopting methanol than methane, and both acetone and ethanol can further increase it. Moreover, as characterized by the X-ray Diffraction (XRD) and Raman spectroscopy, the MCD film fabricated using methane shows much lower total residual stress (σ), better film quality and lower (220)/(111) ratio compared with those fabricated using all the other carbon sources. The above results can be attributed to the presence of oxygen elements, the different dissociation energies of chemical bonds in the carbon sources, the different quantities of CH3 radicals generated from the carbon sources or the different amounts of defects in as-deposited diamond films. Based on the present study, it is suggested that the carbon source should be reasonably chosen in order to, respectively, improve the film quality or obtain high ND, NS and R.