Synthesis and Transfer of High-Quality Graphene Grown on Al2O3(0001)/Pt(111) Template Wafers

Abstract

Today, CMOS compatible routes to grow and transfer large graphene sheets are still missing. Chemical vapor deposition (CVD) is the main synthesis technique yielding high-quality wafer-scale graphene. Platinum is expected to be an excellent catalyst to grow monolayer, large scale and high-quality graphene. Moreover, electrochemical graphene transfer methods are demonstrated, which facilitate the reusability of this expensive Pt template. A process window is studied to grow graphene on platinum foils. The influence of growth temperature and time as well as the methane to hydrogen ratio is optimized. Moreover CO2 can be used as a graphene defect etching gas to replace hydrogen, resulting in successful graphene syntheses conditions. It is shown that the polycrystalline nature of the Pt foil makes it extremely difficult to grow a uniform monolayer graphene sheet. It is also demonstrated that a smooth Pt(111) thin film on sapphire (Rrms = 0.2 nm) decreases the amount of graphene nucleation centres and thus strongly reduce the graphene multilayer areas. Therefore, a Pt(111) thin film appears ideally suited to grow millimetre-sized graphene islands in reasonable time frame (< 1 hour growth time). To promote graphene delamination from the platinum growth template, it is of prime importance that an interfacial water (IFW) layer is formed. This IFW layer serves as a pathway for charged ions to intercalate between graphene and its CVD growth substrate. It is demonstrated that only a selection of ions succeed in intercalating and thus in a successful graphene delamination. The ions that are able to intercalate are electro-active outside the electrochemical window of the used solvent. Figure 1