Direct graphene growth on GaN and Au materials using the PECVD method

The great interest in graphene applications in optics and optoelectronics still requires alternative methods for obtaining high-quality graphene. Currently used methods are based on graphene transfer onto a target substrate. As a consequence, the structural quality of graphene is lowered and so are its the electrical and optical properties. What is more, the transferred graphene layer is often contaminated with Cu, Ge or chemical residue. As a result, such a graphene layer can only be used in limited applications. Better quality is required when the 2D material is to be applied as a transparent conductive electrode (TCE) in a GaN-based light emitter or as an active layer in an Au-containing optical fibre. Therefore, alternative methods for graphene deposition are still in demand. In this work, a plasma-enhanced chemical vapour deposition (PECVD) process was used for direct graphene growth on GaN and Au substrates in the Aixtron Black Magic system. This method does not require chemical isolation, graphene transfer or a metallic catalyst. The entire process can be conducted in stable and repeatable conditions. Structural homogeneity of obtained graphene was observed using scanning electron microscopy. Its presence and overall optical characteristics were investigated with Raman spectroscopy over a large area (mapping mode). They confirmed the formation of graphene and its dependence on growth time through the presence of the 2D mode. The results prove that PECVD is a promising method for obtaining graphene in the form of flakes.