Effect of hydrogen on chemical vapor deposition growth of graphene on Au substrates

Chemical vapor deposition (CVD) on substrates with low C solubility such as Cu and Au is promising to grow monolayer graphene selectively in a large scale. Hydrogen is often added to control the domain size of graphene on Cu, while Au does not require H₂ since Ar is inert against oxidation. The effect of H₂ should be revealed to improve the quality of graphene on Au. Here we report the effect of H₂ on the CVD growth of graphene on Au substrates using in situ radiation-mode optical microscopy. The in situ observation and ex situ Raman spectroscopy revealed that whether H₂ was supplied or not strongly affected the growth rate, thermal radiation contrast, and compressive strain of graphene on Au. We attributed these features to the surface reconstruction of Au(001) depending on H₂ supply. Our results are essential to achieve the graphene growth with high quality on Au for future applications.