Preparation And Properties Of Dianmon/Nanostructure Carbon Field Emission Composite Cathodes

Diamond thin films have a variety of excellent properties such as high thermal conductivity,high breakdown voltage,radiation resistance,low coefficient of thermal expansion,and chemical stability,which have been considered as one of the most important candidates in next-generation semiconductor devices.Due to its high electron field emission efficacy,diamond thin films are promising to be utilized as cold cathodes for flat panel display or cold electron emitters for flat panel display,high power microwave tubes and other fields.In recent years,several types of nanostructure carbon-based thin film including nanosheets,nanotubes,nanorods,nanoparticles,nanofibers,etc,have been developed rapidly by exploiting their unique optical,electrical,chemical,physical,mechanical,and piezo-electrical properties.They are of great interest as cathode electron sources,due to their low threshold emission fields.Much attention has been paid to carbon-based emitters which have good field electron emission properties.At present,many preparation methods have been used for the synthesis of carbon-based films such as oxidation-reduction method,rod coating method,epitaxial growth method,layer-by-layer method and chemical vapor deposition（CVD）method.Comparing to the other methods,the CVD method provides larger area and higher morphology density of carbon-based films,better-controlled process,and absence of electrode contamination while good cost-efficiency can be maintained.In this study,a field emission composite cathode has been prepared on silicon substrate by microwave plasma chemical vapor deposition（MPCVD）method.The synthesis was obtained by first depositing a layer of diamond on silicon and then depositing a top layer of nanostructure carbon.Experimentally,the surface morphology and structure of the synthetic materials were characterized by Scanning Electron Microscope（FE-SEM）,X-ray diffraction（XRD）spectrum,and Raman Spectroscopy.Their field electron emission properties were measured by a CS-380 high voltage measurement unit at a high vacuum of 1×10^-4Pa.The materials showed more than two times higher field emission maximum current density than that of the single layered nanostructure carbon cathodes prepared under the same experimental conditions.They also exhibited enhanced field emission properties and lower turn-on field as compared with diamond layer alone.These two phenomenons were explained reasonably.The resultsdemonstratedthatdiamond/nanostructurecarbonfield emission composite cathodes would be very efficient and promising.