| The technology of graphene cold cathode preparation by electrophoretic deposition is one of the most popular cold cathode preparation technologies currently. Graphene, with good electronic conductivity, high mobility, high aspect ratio and other advantages, is the ideal material for cold cathode electron emission. Electrophoretic deposition method with the advantages like low cost, making device simple, controllable deposition thickness, suitable for large-scale preparation has huge advantages in cold cathode preparation technology. Study on the electrophoretic deposition technique for the preparation of graphene cold cathode in favor of the application for graphene cold cathode in vacuum electronic devices, especially for field emission display.This thesis research graphene cold cathode preparation by electrophoretic deposition method mainly focus on the aspects of lowering the turn-on field and threshold field and improving the field emission stability and life, so that it could better apply in electronic vacuum devices, especially in field emission display device. Therefore, the thesis mainly focuses on the following two aspects:On the one hand, starting from the electrophoretic parameters, through a combination of experiments to theoretical research of electrophoresis parameters influence on the field emission properties of graphene, we analysis and study the method of how to make good field emission properties graphene cathodes under different electrophoretic conditions. And we have focused on the effect of different nitrate salt, which used in electrophoretic deposition liquid, on the field emission of graphene cold cathode prepared by electrophoretic deposition. Research shows that: Mg(NO3) 2.6H2 O prepared graphene cold cathode has the optimal field emission properties, the turn-on field is 3.3 V/μm and the threshold field is 6.3 V/μm. The reasons for explaining this phenomenon is that on the surface of graphene cold cathode appears graphene-magnesium oxide hetero-junctions produced a field enhancement under the process of the external electric field increase. So the graphene cold cathode has the better field emission characteristics. On the other hand, starting from the field emission mechanism of graphene, through surface modification we enhanced the field emission properties of electrophoretic deposition prepared graphene cold cathode. We improved the field emission properties of graphene cold cathode surface by sputtering magnesium oxide nanoparticles using radio frequency magnetron sputtering. In Zn(NO3)2.6H2 O prepared condition, the best time is 20 seconds. The field emission tests indicate that: sputtering magnesium oxide nanoparticles lower the graphene cold cathode turn-on field from 6.3 V/m to 3.8 V/m, threshold field from 9 V/m to 6.5V/m. Field enhancement factor increased from 1123 to 2386. The reasons of explaining this phenomenon is that magnesium oxide nanoparticles have low electron affinity lowering the work function of the material surface, and increase the number of graphene surface electron emitters, which improves the field enhancement factor. The field emission stability test showed that the sputtering magnesium oxide nanoparticles also improved the stability and life of the field emission of graphene cold cathode. Because of the vacuum deterioration by residual gas and field emission, this method will play an important role for helping keep the stability of field emission of graphene cold cathode in field emission display device.The research results of this thesis are beneficial for graphene cold cathode prepared by electrophoretic deposition to apply in electronic vacuum devices, especially in field emission display device. |
