Control of Plasma-Dielectric Boundary Sheath Potential for the Synthesis of Carbon Nanomaterials in Surface Wave Plasma CVD

Surface wave plasma (SWP), produced using microwave power, has attracted considerable attention for use in chemical vapor deposition (CVD) for the synthesis of carbon nanomaterials. In our previous work, a method, in which a negative direct current voltage is applied to a thin metal plate attached to the dielectric window, was reported for the reducing of plasma space potential in an SWP. Here, we demonstrate that a sheath potential >180 V, created at the plasma-dielectric boundary by the method, allows the synthesis of diamond-embedded carbon thin films even on nonpretreated silicon substrates at a gas pressure as low as 30 mTorr and a substrate temperature as low as 420 °C with a low CO concentration (2%) in H₂ gas. These results show that the control of the sheath potential at the plasma-dielectric boundary can enhance the performance of an SWP in CVD applications.