Direct Synthesis Of Doped Graphene On Dielectric Substrates Using Solid Carbon Sources

Graphene has attracted intense research interests due to its extraordinary physical and chemical characteristics, such as good mechanical strength, high carrier mobility, excellent electrical conductivity, superior thermal conductivity and high transmittance. However, the nature of pristine graphene with zero band gap brings some difficulties for its application in the electronic device field. Doping of graphene with other heteroatoms(e.g., nitrogen, boron, phosphorus, halogen, etc.) is the most practicable, convenient and efficient approach to modulate the band structure and properties of graphene and further extend more useful applications in electronics and electrochemical cells. Various methods of graphene synthesis have been developed, including chemical vapor deposition(CVD), chemical reduction of graphene oxides, and organic synthesis from micro molecules. Among the methods, graphene synthesis by CVD on metal catalyst films has unique advantages for large area and uniform graphene formation for electronic applications. However, in all methods, it is necessary to physically transfer the grown graphene onto desired substrates for subsequent device processing. During the transfer process, great care must be taken to avoid introducing defects into the graphene sheet. Hence, intense efforts have focused on developing alternative synthetic methods that can avoid transfer.Direct synthesis of high-quality doped graphene on dielectric substrates without transfer is highly desirable for simplified device processing in electronic applications. Graphene synthesis directly on substrates suitable for device applications, though highly demanded, remains unattainable and challenging. In this thesis, a new method was introduced using polycyclic aromatic hydrocarbons(such as pentacene, Alq3, TPB and F16CuPc) as solid carbon sources, Cu as a metal catalyst, to directly synthesize graphene film on insulated substrate without transfer process. The study found that small organic molecule with a planar structure is more beneficial for the growth of the graphene film. We systematically investigate the factors such as heating rate, thickness of carbon source, growth temperature, growth time and thickness of Cu catalyst, which affect the growth quality of the doped graphene and optimized the growth conditions for high-quality doped graphene. The research results show that the optimal growth conditions for the doped graphene growth from TPB were set at 5 nm TPB as solid carbon source, 1000 nm Cu film on the top surface, and annealing temperature of 1000?C for 60 min. Furthermore, N, F-co-doped graphene can be synthesized by using only F16 CuPc as solid carbon source and both N and F doping sources. The properties of as-grown samples were well studied and N, F-co-doped graphene exhibits a high optical transmittance and low sheet resistance. The present growth strategy provides a controllable transfer-free route for high-quality doped graphene growth, which will facilitate the practical electronic applications of graphene.