Fabrication And Excellent Optoelectronic Properties Of Graphene Composites

Graphene has attracted tremendous attention from materials science, nanoelectronics andother discipline fields since its first exfoliation from graphite in2004. Due to its unique electronicproperty, good stability and high aspect ratio, graphene becomes an attractive material of fieldemission, which is the thinnest two-dimensional material in the world. However, there are stillsome drawbacks that can’t overlook, such as nonrigidity and inclination to self-aggregate.Nowadays, a great deal of efforts has been devoted to the study of graphene-based materials. Bydoing these, the merits of graphene have been strengthened and its drawbacks have beenovercome. In this thesis, we have fabricated graphene/ZnSe and graphene/Si nanocone arraysrespectively. Furthermore, the potential applications of graphene composites in optoelectronicproperties are investigated.1. Novel cactus-like and honeycomb-like ZnSe microspheres have been successfully grownon graphene oxide sheets via hydrothermal route, and its optoelectronic properties have beenstudied. The concentration of EDTA plays an important role in the morphologies andoptoelectronic properties of ZnSe microspheres. A large number of cactus-like microspheres withaverage diameter of about10μm are observed when the concentration of EDTA is0.3M. Whilethe concentration is increased to0.45M, honeycomb-like ZnSe microspheres are formed. Theresults of XRD reveal that the as-grown ZnSe microspheres present cubic zinc blende structure. Inaddition, the optical properties of graphene/ZnSe composites are investigated. An obviousabsorption peak is observed at225nm for the cactus-like ZnSe microspheres in the UV-Visspectrum and they exhibit a strong near band-edge emission peak centered at468nm in thephotoluminescence spectrum.2. Large-area graphene film is prepared on the copper foils via low pressure chemical vapor deposition. The film is transferred to the surface of Si nanocone arrays, which are fabricated byAr+ion beam bombardment ahead of time, and sharp protrusions are left within the surface ofgraphene due to good soft of graphene. As control experiments, the film is also transferred to thesurface of Si wafer. Finally, we investigate the potential applications in field emission. Fieldenhancement factor is calculated from the slope of the F-N plot and is closely related withgeometric parameter and shape of emitters. The shape of graphene emitters is similar to that of thetip of Si nanocone due to the good soft of graphene. So the field enhancement factors of grapheneare the same to those of Si nanocone arrays in high electric field region. The high-performancefield emission is mainly attributed to the decreasing work function of crooked graphene, whichdecreases with increasing curvature of Si nanocones.The results indicate that graphene film and its compounds have great potential applications infolding and transparent photoelectric devices in the future.