| Graphene films were synthesized by using microwave chemical vapor deposition method in this paper. Carbon films of different structures synthesized on catalyst films of different kinds and structures have been studied, and the growth process of carbon films of different structures was studied too; the field emission properties of graphene films was tested in order to find graphene films as field emission cathode. The conclusions obtained through research are following:1. Study on structures of carbon films on Ni films:The effect of thickness of Ni films and different deposition temperature on carbon films structures onNi films were studied and found that, the smaller the thickness of Ni films, the smaller size of grain formed in the same temperature. The smaller grain size is beneficial to growth of nanocarbon structure, but the type of carbon structures is not very different. The sample synthesized at500oC is mainly the nano-graphite slice coated on the Ni grain, while the sample synthesized at400oC is the composite of nano-graphite and carbon nanotube; It can be said there is no graphene synthesized on Ni films.2. Study on structure of carbon films on Fe-Ni-Cr films:Carbon films were deposited on Fe-Ni-Cr films by many experiment were characterized by Scanning Electron Microscope (SEM), Raman spectrum and Transmission Electron Microscope (TEM) and the conclusion is that few-layer graphene could be synthesized under certain conditions of PECVD.3. Effect of thickness of Fe-Ni-Cr films and substrates of different kinds on graphene structures:the effect of different thickness of catalyst films and three kinds of substrates on graphene structures was studies and found that:graphene could be synthesized on Fe-Ni-Cr films within certain thickness of films. Fe-Ni-Cr films for ten minutes are benefited to graphene growth. Graphene films of better quality have been prepared on different substrates.4. Discussion of Fe-Ni-Cr on catalyst growth of graphene:the catalyst grain size has effect on growth speed and structural characteristics, the smaller the grain size, the faster the growth speed, the better the growth of graphene. During the CVD process the Fe-Ni-Cr films crystallize again to form bigger grains because of high temperature. Roughness of Si substrate is about0.9nm, while roughness of ceramic is about2μm, Rough surface hindered the growth of Fe-Ni-Cr particles. The particle size of catalyst on two kinds of substrate is about20nm and100nm respectively, and growth of graphene on related Si substrate stopped after10min; while the graphene grown for lmin on ceramic substrate is no more growing with time increasing. In addition, the more the graphene density, the less the layer of graphene due to the little particle size of catalyst.5. Field emission properties of graphene films:opening field of graphene prepared on single silicon substrate for1.2V/μm, at2.4V/m the current density reached900μA/cm2; opening field of graphene prepared on ceramic substrate for1.26V/μm, at2.2V/m the current density reached2.1mA/cm2; opening field of graphene prepared on single silicon substrate for2.17V/μm, at3.67V/m the current density reached6.11mA/cm2. |
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