Temperature dependence of the growth rate for nanocrystalline diamond films deposited from an Ar/CH4 microwave plasma

We have investigated the effect of substrate temperature on the growth rate and properties of nanocrystalline diamond thin films prepared by microwave plasma-assisted chemical vapor deposition on (100) Si from a 1% methane $({\mathrm{CH}}_{\mathrm{4}})$ precursor in argon (Ar). In previous work we have shown that the carbon dimer ${\mathrm{C}}_{\mathrm{2}}$ is the dominant growth species for this ${\mathrm{CH}}_{\mathrm{4}}\mathrm{/Ar}$ system without the addition of molecular hydrogen. In the present work, the apparent activation energy for this growth process from ${\mathrm{C}}_{\mathrm{2}}$ was determined from a standard Arrhenius-type analysis of the growth rate data for substrate temperatures between 500 and 900 °C. The measured value of $\text{5.85±0.438\hspace{0.17em}}\mathrm{kcal/mol}$ $\text{(0.254±0.019\hspace{0.17em}}\mathrm{eV/atom})$ is shown to be in close agreement with the results of recent modeling studies of the energetics of ${\mathrm{C}}_{\mathrm{2}}$ addition to the diamond $\text{(110)–(1×1):}\mathrm{H}$ surface. These results have important implications for low-temperature diamond coating of nonrefractory materials such as glasses.