Chemical vapor deposition of carbon films: in-situ plasma diagnostics

Chemical vapor deposition (CVD) is conventionally used to create a variety of carbon mesomaterials including polycrystalline diamond films and carbon nanotubes (CNT). The remarkable flexibility of the CVD process allows one to create materials with dramatically different properties (e.g. diamond, graphite and CNT films) by changing the geometry of the reaction chamber and discharge type. Moreover, very recently we have shown that diamond, graphite and CNT thin film materials can be grown in the same dc discharge CVD system by varying the pressure and composition of hydrogen-methane mixture along with discharge current and voltage. These results, which have been obtained from the Raman measurements, electron microscopy and also from the measurements of the electron field emission efficiency, are summarized in Table 1. However, the parameters of CVD process used have been found to be very close to an unstable regime, in which spontaneous arcing may destroy the substrate and electrodes. In this work, we reveal the characteristics of the CVD process that ensure a stable discharge. Also, we observe the presence of CH-, C2-, H-, and H2-activated species responsible for different carbon species formation in the CVD plasma on substrate and direct condensation of carbon in plasma gas phase at higher methane concentrations.