Research Of The Preparation Of Nanocrystalline Diamond Films By Direct Current Glow Discharge CVD Method

Ultra-nanocrystalline diamond（UNCD）is a new concept,which has been put forward in recent years,in artificial nano-diamond field.Usually,the grain size of UNCD is less than or equal to 10 nm.Besides high hardness,good wear resistance,UNCD possesses the advantages of low surface roughness,good electricity quality etc.These advantages let UNCD films have potential application prospects in machining and mechanical sealing,MEMS\NEMS,field emission devices,SAW devices,optical windows,biomedicine etc.Technologic parameters of producing UNCD films were systematic researched in DC GD CVD device and MPCVD device.Improvement of related components in long-time deposition were also proposed.In hydrogen and methane environment,the influences on topography and quality of UNCD films of pretreatment,methane flux,substrate temperature,deposition pressure were the main researches.UNCD films were analyzed by testing instruments like SEM.The results of researches show that pretreatment has positive influence on enhancing nucleation density.A very high nucleation density can be obtained by using a hybrid CVD nucleation(1.0×10¹¹ nuclei/cm²).With the methane flux increasing,the grain size decreases.The quality of films would be worse cause of high methane flux.Satisfying quality and grain size can be obtained when H₂/CH₄ is 500/35 sccm.With the substrate temperature increases,the grain size increases.The grain size would increase into micro scale cause of excessive temperature.Satisfying quality and grain size can be obtained when temperature is 700°C.With the deposition pressure increases,the compactness of films increases at first,then decreases and the ball-like clusters in films changes into irregular clusters.Satisfying compactness and uniformity can be obtained when deposition pressure is 50 torr.The two main factors（gas field distribution and the discharge situation of cathode）,which influence the long-time deposition markedly,were researched.A long-time deposition（100h）were carried out after the improvement of related components.The UNCD films was analyzed by kinds of testing and characterization.The results indicated that the grain size of UNCD films up to 10 nm scale,the roughness is 22.3 nm and the deposition rate is 0.61μm/h.