| Graphene has drawn more and more attention nowadays, because it has unique properties and widely applications. It has been widely studied in transparent electrodes and electrochemical capacitors. And its high aspect ratio(the ratio of lateral size to thickness) also made it a field emission material. There are many methods to made graphene, but in our study we use the methods of chemical oxidation method and ultrasonication dispersion method.Electrophoretic deposition is an industrial technique. And in this thesis, it has been widely used to fabricate fluorescence screen and graphene based field emission cathodes. Specially, we fabricate graphene oxide based cathodes. They have similar experiment condition, but the fabrication of graphene oxide based cathodes need much higher electric field.Then we test the filed emission property of these cathodes. What is more, graphene oxide cathodes can be reduced to graphene cathodes by thermal annealing, and its filed emission property improved. We study the influence of different annealing temperature, and we get the optimal temperature. At this temperature of 600°C for 40 min, the cathodes reach the best filed emission property, ant the turn-on field was 3.4V/μm, and the threshold field 6.8V/μm.At last, we introduced the surface modification of graphene by laser irradiation and we test the field emission of the modified cathodes. We analyze the difference of laser surface modification and thermal annealing. We found that the optimized laser irradiation time was 15 seconds, and it was better than that of thermal annealed methods. The turn-on field was decreased from 3.4 to 2.4V/μm, and the threshold field was reduced 1.7V/μm. Scanning electron microscopy was taken to reveal the change of morphology after surface modification, and it made much higher field enhancement factor. The field enhancement factor of sample after laser irradiation for 15 seconds reach a value of 5469, while the annealed samples was 3464 at 600°C. TiO2 emerged at interface of the graphene and Ti substrate in high temperature thermal annealed. And this limited the improvement of its filed emission property. The stability of graphene cathodes by laser surface modification was more stable than thermal annealed sample. And it can light up fluorescence screen with a clear outline. These made the graphene cathodes as a potential field emitter. Graphene cathodes must lead the next revolution of flat-panel display. |
