Preparation Of Multilayer Diamond Films By MPCVD

CVD diamond performs well in the thermal,electrical,optical and many other fields as an advanced material and excellent properties attracts wide attentions in the research area.The micro-scale CVD diamond film has good hardness,thermal conductivity,adhesion,but its surface is quite rough and difficult to produce.The nano-scale CVD diamond film has smooth surface,good electric performance and is easy to doped,but the growth rate is slow and contains a large amount of non-diamond phase.The application prospect of CVD diamond film can be exploited by combining the excellent properties of micro and nano diamond film.The multilayer diamond film technology is a kind of good method.But there are still some difficulties in the this area like the control of structure,the number of layers,the performances and quality of deposited films,the industrial production and so on.Against the problem discussed above,this study explored the problems related to the preparation of multilayer diamond films by using the R2.0 type MPCVD device of Woosinent company in Korea and the self-made 75kW MPCVD device.The primary results in this research are listed following:1.The controllable growth of diamond films was investigated in H₂/CH₄/CO₂atmosphere.The results show that CO₂ has a great influence on the surface morphology and quality of diamond films,appropriate addition of CO₂ can improve the quality and the growth rate of the films,and CO₂ can promote the growth of?111?plane,but is not conducive to the growth of?100?plane.The micro-diamond films with different morphologies?pyramid morphology and?100?morphology?and nano-diamond films were successfully prepared by regulating the concentration of CO₂.2.Double-layer,three-layer and four-layer diamond films were prepared.In the process of deposition of micro-nano double-layer diamond films,secondary nucleation rate increased after micron layer nucleation,and the growth of the nano-layer on the?100?-faceted micro-diamond film is more difficult than on the?111?-faceted micro-diamond film.The three-layer diamond films with micro/nano/micro structure were prepared,the performance of the diamond film is mainly affected by the thickness of the nano-layer,and the thicker the nano-layer is the higher internal stress of the diamond film is.Four-layer?micro/nano/micro/nano?diamond films were prepared by alternating deposition of micro and nano layers.Through the analysis of the surface roughness,it can be seen that the growth of nano-layer after micron layer nucleation and the increase of the number of layers can significantly reduce the surface roughness,and obtain the four-layer diamond film with surface roughness of 65.9nm?Ra?.3.Based on the study of the preparation of multilayer films,a possible growth model of multilayer diamond films is proposed.In the process of multi-layer diamond film growth,there is an obvious transition layer from the micro layer to the nano layer,but no obvious transition layer from the nano layer to micro layer.It is found that the thickness of the transition layer is related to the surface roughness of the micro layer,the rougher the surface is and the thicker the transition layer is.4.Three layers of diamond films were prepared on 75kW MPCVD device.The effect of gas pressure on the diamond film was studied.The quality of the diamond film increasing firstly and then decreasing with the increase of gas pressure,and three layers of diamond films were prepared by adjusting the deposition pressure.