A New Process For The Preparation Of DLC Films By Medium Frequency Magnetron Sputtering And ECR-CVD

This work mainly focuses on the preparation technology of hard DLC coatings using a combined equipment of electron cyclotron resonance(ECR)and medium frequency magnetron sputtering.The performance of the DLC coating were characterized.DLC thin films were deposited on singlecrystalline silicon wafers using ECR-CVD and intermediate frequency magnetron sputtering.For the CVD method,C2H2 was used as the carbon source of DLC films and Ar was used as the working gas.For medium frequency magnetron sputtering method,high purity graphite targets were used as the carbon source and argon was used as the working gas.After a series of complicated physical or chemical process,DLC films were successfully deposited on singlecrystalline silicon substrates.The surface morphology of the films was analyzed.The deposition rate of the films prepared by magnetron sputtering and ECR-CVD were measured.The structural characteristics of the films were analyzed.The hardness,elastic modulus and binding force between the film and the substrate were measured,too.We also investigated the effect of annealing on the properties of DLC films.For the magnetron sputtering method,cathode with strong magnetic field was introduced,which is more intense than the conventional cathode and can restrain more electrons bombarding the graphite target so as to improve the ionization rate and enhance the sputtering energy of the carbon ions,resulting higher deposition rate.The effects of sputtering current,argon flow rate and negative bias voltage on the properties of the films were investigated systematically.The hardness of the prepared DLC film is better when the sputtering current was 0.85 A,the flow rate of argon was 20 sccm and the negative bias was 50 V.The maximum hardness obtained by this method was 17.8 GPa,and the binding force between the film and the substrate was 18.48 mN.For ECR-CVD method,an effect of cutting-edge discharge was introduced for the preparation of DLC films.The purpose was to increase the density of plasma and test the influence of some critical experimental conditions on the properties of DLC film.Compared with the conventional DLC film prepared by ECR-CVD,the hardness of DLC film is better.The hardness of DLC film prepared by ECR-CVD method can reach about 30 GPa,with the highest hardness value of 30.84 GPa and the binding force between film and substrate of 103.93 mN.Therefore,the hardness performance and the binding force between film and substrate of DLC films prepared by ECR-CVD method is much better than those of DLC films prepared by magnetron sputtering method.In industrial applications,the hardness properties of DLC films prepared by ECR-CVD have been as high as the hardness requirements of hard coatings.Annealing treatment would lead to some cracks in the surface morphology of the DLC film,which might result from the improper annealing process.When the annealing temperature reaches a certain temperature,large grains appeared and some part of the film would peel off the substrate.The SP3 content of DLC film decreased with the increasing of annealing temperature,which leaded to the decreasing of hardness and elastic modulus of DLC.The binding force between the film and the substrate was enhanced when the annealing temperature was 200 °C.When the annealing temperature is higher,the binding force between the film and the substrate was weakened.