Effects Of Secondary Nucleation Ratio On The Diamond Films

As the technology development,CVD diamond has incomparable physicochemical property as well as the natural diamond and obtained great prospect in various applications.Microwave plasma CVD has the characteristics of electrodeless discharge and won't pollute the deposition environment,which is identified as the best method to prepare from micro(MCD),to nano(NCD),and to ultra-nanocrystalline diamond(UNCD).At home and abroad,researchers were focused on how to control the growth of diamond films at present.By means of adding inert gas and controlling the concentration of CH4,the fundamental goals are finding a way to control the internal reaction mechanism.Secondary nucleation,as one the significant process of diamond film growth,which can influence the changes in the surface morphology and growth conditions based on it's ratio,during the diamond film deposition.Therefore,research on how to control secondary nucleation process and study how it's influence on diamond film deposition when the ratio is high or not are of great significance.In this paper,all experiments have been taken by R2.0-MPCVD apparatus which designed by Woosinent company and home-made bell-jar type MPCVD apparatus respectively.Using CH4/H2/Ar and CH4/H2 as gas resources,the effect of the secondary nucleation on diamond growth were discussed in detail.The primary results in this research are listed following:1.When using CH4/H2/Ar as gas resource,while the concentration of Ar is under a threshold(92.5sccm),the diamond films are mainly composed of microcrystalline grain.when up to 92.5sccm,There are small quantity of crystal nucleus due to secondary nucleation at the crystal boundary;2.With adding insert gas(Ar),secondary nucleation has been influenced: when up to95.0sccm,this phenomenon has been promoted.the crystal nucleus which form at boundary increased significantly,suppressing the initial grain growing up the rate of secondary nucleation increased and grain size decreased;the "cauliflower-like" nanocrystalline diamond and "ballas-like" ultrananocrystalline diamond on the surface when the concentration are 95.0sccm and 97.5sccm respectively.3.When using an argon rich environment(>95.0sccm),due to the less of H atom in plasma,the effect of etching was been weakened,make the content of diamond phase decreased,meanwhile,the amorphous carbon and graphite content increased.And the films tend to(111)preferential growth.4.While diamond films are deposited in CH4/H2,with the increase of the concentration of CH4,the structure changed obviously.When the concentration of CH4 increased from 1.0% to 2.5%,the grain size decreased as well as the quality of the films because of the high concentration of CHx.