PECVD Synthesis of Vertically-Oriented Graphene: Mechanism and Plasma Sources

The plasma-enhanced chemical vapor deposition (PECVD) method is a key method for synthesizing vertically-oriented graphene (VG). Because the plasma region provides active species (e.g., energetic electrons, excited molecules and atoms, free radicals, and photons), PECVD offers several advantages in nanostructure synthesis, e.g., a relatively low substrate temperature, a high growth selectivity, and good control in nanostructure ordering/patterning. These features make PECVD the most suitable method for VG growth. On the other hand, the growth of VG using PECVD is a quite complex process due to the complexity of plasma chemistry. The morphology and structure of the VG sheets produced by PECVD are strongly dependent on the types of plasma sources and a series of operating parameters, such as feedstock gas type and composition, the substrate temperature, and the operating pressure. In this chapter, we first discuss the growth mechanism of VG in a PECVD process and then discuss how plasma sources affect the VG growth. Characterization of PECVD-produced VG from various plasma sources using Raman spectroscopy, a powerful tool to study carbon nanostructures, is also discussed in this chapter.