Chemical Vapour Deposition of Large-area High-quality Graphene Films for Electronic Applications

Abstract

Low Pressure Chemical Vapour Deposition (LPCVD) and transfer processes are explored and optimized to obtain large-area, continuous and high quality monolayer graphene on target substrate. The size of synthesized graphene reaches up to 20 mm * 20 mm, and can be further extended by upgrading to a larger reaction chamber; the monolayer coverage rate and conductivity is better than normal commercial graphene products on the market. A novel frame-assisted method is developed to transfer graphene without introducing many defects and impurities. Annealing and acetone treatment are combined to remove PMMA residues effectively and unharmfully. A new under-etching route to fabricate graphene free-standing structure is also proposed and explored. A novel non-contact microwave examination method has been employed to simplify the sheet resistance measurement processes and to avoid the effects of metallic contacts. This method is simple and non-destructive to graphene, and can be further integrated into the graphene production line in the future. A new double-layer device is fabricated and utilized to observe the microwave field effect in graphene. The interaction between graphene and oxygen under different temperatures and oxygen partial pressures is studied and discussed. Strontium Titanate films (SrTiO3 or STO) are deposited on transferred CVD grown graphene on MgO substrates. Based on the oxidation test result, the deposition process of Strontium Titanate is optimized to minimize the defects introduced on graphene. Raman mapping data show that graphene is still continuous after the STO deposition although the D band suggests some newly formed defects.