| In this article,the effects of nitrogen,argon,helium and argon-nitrogen gas mixture on the nanocrystalline diamond films were studied by hot filament chemical vapor deposition.The OES was used to in situ measure the plasma on the diamond growth,and the quality and morphology of grown diamond films were investigated using SEM、XRD and Raman spectra.The research contends include as following:In the acetone/H2/N2 system,when the nitrogen volume fraction is more than 40%,the grain size of the diamond film begins to appear nanocrystalline,and the growth rate of the diamond film is proportional to the nitrogen concentration.The results of optical emission spectra show that,when the concentration of nitrogen increase,the intensities of Hα,Hβ,C2,CN and other groups become powerful,the radical of CN is more effective than the reactive hydrogen to extract the hydrogen atoms on the surface of the film,it can improve the secondary nucleation rate of the nanocrystalline diamond film.In the acetone/H2/Ar system,the growth rate of the diamond film increases with the raise of argon concentration.The grain size of the film is gradually refined with the increase of the argon concentration.The analysis of the optical emission spectrum indicates that,the Hα,Hβ,C2,CO groups show an increasing trend with the increase of argon concentration,and the electron temperature also increased with the raise of argon concentration.In the acetone/H2/He system,the results are similar to those in the acetone/H2/Ar system,but the intensity of the active radicals and the value of electron temperature are lower in the acetone/H2/Ar system.The reason is that the argon and helium all belong to inert gas,the influence mechanism of them are similar.The value lower is attributed to the metastable excitation potential of argon is 11.55eV,which is lower the metastable excitation of helium（19.77eV）.In this way,the argon is easier to be excited.So it has greater ionization cross sections.It is found that the effect of nitrogen on the growth rate of nanocrystalline diamond films is mainly by changing the chemical reaction kinetics process during the growth process,while the inert gas affect the growth rate through physical action.And the effect mechanism of argon is similar to helium,the effect of argon is stronger than helium under same concentration.Therefore,we choose the argon and nitrogen as the mixed gas to deposit nanocrystalline diamond.In the acetone/H2/Ar/N2 system,When the argon-nitrogen mixed gas volume accounts for 20%of the total volume,the sample of deposited is microcrystalline diamond,but the growth rate is higher than the samples deposited by single auxiliary gas in the same ratio.When the argon-nitrogen mixed gas volume accounts for 40%of the total volume,the secondary nucleation rate increases significantly which leads to nanocrystalline,and the growth rate is higher than the samples deposited by single auxiliary gas in the same ratio.When the argon-nitrogen mixed gas volume accounts for 60%of the total volume,the growth rate of the samples is further improved.When the concentration of argon and nitrogen at 30%,the growth rate of nanocrystalline diamond was highest,its growth rate is 4.6μm/h.With the increasing of nitrogen volume fraction,the ratios of CN/Hαwas increase,while the ratios of C2/Hαgradual decrease,and the nitrogen additon favours the formation of a（400）textured.The Raman results show that when the argon nitrogen mixed gas accounts for 60%of the total volume,the nanocrystalline diamond films have good quality.When the argon-nitrogen mixed gas accounts for 80%of the total volume,the rate of deposited nanocrystalline diamond film increases,but the quality is poor.Finally,we deposited high-rate micron/nano-diamond composite films by adding 30%nitrogen and argon respectively. |
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