The Role of Pre Hydrogen Flow in Nucleation of Graphene on Silicon Nitride

Graphene has been considered as one of most attractive materials in nano-scaled electronic devices. Graphene film has been mainly grown on many metal (eg., Ni , Cu, Fe) by chemical vapor deposition (CVD) process and transferred on dielectric substrate. However, the complicated transfer techniques for metal-catalyzed graphene inevitably have resulted in wrinkles, holes, and metal etching residues. Thus, there is a substantial need to develop a scalable method for reliable production of large-area graphene directly on insulating substrates.

 We synthesized the nucleation of graphene on silicon nitride (Si₃N₄) substrate and report the influence of pre hydrogen flow during CVD process on silicon nitride which is the stable dielectric and suitable for carbon diffusion barrier. Test wafer was cleaned in 10:1 HF solution and nucleation of graphene was synthesized by CVD process using CH₄, Ar, H₂gas at 1000°C.

 We evaluated the graphene nucleation with and without pre hydrogen flow on silicon nitride film as shown in Fig.1. Although amorphous carbon cluster was formed on silicon nitride without pre hydrogen flow as shown in Fig. 2(a), Raman shift peak related graphene was obtained with pre hydrogen flow condition as shown in Fig. 2(b). It is assumed that hydrogen ions are bonded with silicon atom on silicon nitride surface during pre hydrogen process and then chemisorptions of carbon precursors on the H-terminated surface are easily made. Fig.3 shows the role of hydrogen [1]. To synthesize the graphene film on silicon nitride, it is essential to be terminated with hydrogen at silicon nitride surface.

Reference

[1] Jae-Hyun Lee et al, “Wafer-Scale Growth of Single-Crystal Monolayer Graphene on Reusable Hydrogen-Terminated Germanium”, Science, Vol. 344, 2014