Growth And Characteristic Reasearch Of Graphene On The Surface Of SiC, Sapphire And Cu Foil

Graphene, a new carbon material which was confirmed in2004, because of its unique two dimension honeycomb crystal structure and strange band structure, have attracted more and more attention recently. Graphene exhibits excellent optical, thermodynamic, mechanical and electrical properties and will be widely applied in many fields such as nano-electrical devices, super capacitors, photoelectric device, energy storage and so on. The preparation of the graphene with high quility is still a key challenge. In order to design the graphene devices, the graphene layers with large area, stable structure and constant layer number are seriously required. At present, several methods to prepare graphene have attracted more and more attention recently, such as annealing α-SiC at high temperature, preparing graphene layers on the suitable substrate, preparing graphene on the Cu foil substrate and so on. However, the graphene layers with these methods need to be improved and some physics problems have not yet been resolved. In this thesis, we have researched the optimization growth and formation mechanism of the graphene on the SiC substrate, Sapphire substrate and Cu foil substrate by SRPES、Raman and NEXAFS.In need to prepare graphene layers with high quality on the6H-SiC substrate, we have researched the growth process and formation mechanism of the graphene on the two polars of6H-SiC systemically, and developed several methods to improve the crystal quality of the graphene grown on the6H-SiC, including assistance of carbon flux and depositing Ni layer. Moreover, we have made use of three methods to prepare graphene on the sapphire substrate directly, including growing SiC thin film and annealing, growing SiC thin film and Ni layer then fast annealing, directly depositing carbon atoms at high temperature. In addition, we tried to supply solid carbon source to prepare high quality graphene layers on the Cu foil substrate and optimize the growing conditions, also we have developed the methods to control the layer number of the graphene on the Cu foil and to transfer the graphene layers to other substrate. The main work and results are listed as following:1. The growth of graphene on6H-SiC single crystal1) The formation processes of graphene fabricated by thermal decomposition of the6H-SiC (0001) and6H-SiC (0001) were in-situ investigated by Low energy electron diffraction (LEED) and synchrotron radiation photoelectron spectroscopy (SRPES). The results showed that graphene layers were produced finally on the two poplars. The comparisons studies indicated that Si terminated EG appeared highly oriented while C terminated EG anisotropy, and interface interaction similar to C-sp3bond of diamond existed on the Si terminated EG, the interaction between the epitaxial film and substrate was stronger, while on the C terminated EG there was no such interaction, the interaction between the epitaxial film and substrate was weaker. The formation temperature of Si-terminated EG was150℃higher that of C terminated EG. The.flatness of Si-terminated EG is better than that of C terminated EG.2) The effect of of assistance of carbon flux on the graphene grown on the6H-SiC (0001) and6H-SiC (0001) substrates were studied. Results indicated that with assistance of external carbon flux, we can obtain high quality graphene layers and could control the thickness of graphene layer. The results of6H-SiC (0001) showed that graphene can be grown at lower temperature(800℃) when carbon atoms were deposited, and the crystal quality of graphene improved with the substrate temperature increased. The results of6H-SiC (0001) indicated that assistance of carbon flux should be in appropriate evaporation rate.3) Few-layer graphene (FLG) has been prepared by thermal annealing of SiC crystal at low temperature by depositing Ni layer. The effect of annealing temperature on the graphenen crystal quality was also studied. The results revealed that this method would greatly decrease the required high temperature and improve the crystal quality of graphene. As the annealing temperature increased, the crystal quality of graphene first improved and then decreased, and the optimized temperature was800℃.2. The preparation of graphene on sapphire substrate1) SiC thin film was firstly grown on sapphire substrate by SSMBE and then annealed the sample at high temperature to prepare graphene layers. The results showed that we first prepared6H-SiC thin films with high quality and then got graphene layers finally. The prepared graphene films just like the graphene prepared by annealing6H-SiC (0001) and displayed AB stacking structure.2) SiC thin film was firstly grown on sapphire substrate, and next amorphous Ni layer was deposited on the surface, and then the samples were fast annealed and cooled to prepare graphene layers. The results showed that we have got the graphene layers on the sapphire using this method, and the crystal quality of the SiC buffer was critical to the final graphene layers.3) FLG has been grown on sapphire substrate by directly depositing carbon atoms in an ultrahigh vacuum (UHV) molecular beam epitaxy (MBE) chamber. The experimental results confirmed the formation of graphene layer. The mean domain size of graphene was around12.2nm and the layer number of the graphene films was estimated to be2-3. The grown graphene layers on sapphire substrate showed the turbostratic stacking structure, almost the same stacking structure as the FLG produced by annealing C-terminated a-SiC surface, which indicated that they may have similar behavior.4) The preparation of graphene on sapphire substrate1) Graphene had been grown on sapphire substrate by directly depositing carbon atoms. The experimental results showed that we prepared graphene films with high quality. The crystal quality was so high that it much better than those of graphene on the Si and sapphire single crystal prepared by the same method.2) The effect of substrate temperature on the growth of graphene film on Cu foil by directly depositing carbon atoms were investigated. The results indicated that the substrate temperature played an important role in the formation of graphene film. The crystal quality of the graphene improved as the substrate temperature increased and the best graphene was obtained when the Cu foil was melting.3) The methods to control the layer number of the graphene on the Cu foil and to transfer the graphene layers from Cu foil to SiO2/Si were explored. The experimental results showed that we could control the number of the graphene layer by depositing specified carbon atom layer, and we have successfully transferred the graphene layers from Cu foil to SiO2/Si.