The Study On DLC Films Deposited By PECVD

This paper studies the DLC films deposited by using two of the plasma-enhanced chemical vapor deposition (PECVD), pulsed plasma enhanced chemical vapor deposition (Pulse-PECVD) and RF plasma enhanced chemical vapor deposition (RF -PECVD) , We discuss the process features , the relationship between the DLC film performance and the pulse plasma parameters during the pulsed glow discharge, and the relationship between the RF power, the RF self-bias and the air pressure. We analyze the relationship between the technical parameters and the structure and properties of the thin films. In order to achieve the purpose of industrial applications, the coating parameter has been optimized.We prepared the DLC films by using Pulse-PECVD, and study the best processing parameters of the films from the pulse peak voltage and gas component. And we analysis of the surface morphology of the film, composition, structure and mechanical and tribological properties by using SEM, XRD, Raman spectroscopy, and the friction and wear nano-indentation technical. The results showed that we prepared the DLC films dense, smooth surface by using Pulse-PECVD. With the pulse peak voltage from 2 kV to 4 kV, the roughness of thin film decreases, the friction coefficient decreases also, hardness and elastic modulus also by 18.2 and 160GPa increased to 19.6 and 175GPa. With acetylene flow increasing, the roughness of thin film decreases, friction coefficient from 0.172 lower to 0.119, and the hardness and elastic modulus also by 15.9 and 145GPa increased to 19.6 and 175GPa. When the content of acetylene is lower, there isn't a clear Raman characteristic peaks to prove that the films is DLC films, and it also prove that the content of acetylene is the main factors of forming uniformity film.We also prepared DLC films by using RF-PECVD. From the study of Raman spectroscopy, we find that when RF power increased from 500 W to 700 W, the I_D/I/_G ratio increasing from 0.66 to 1.14, it indicates that the sp~2 clusters size increases with the RF power. According to the nano-indentation, the hardness and elastic modulus decrease from 12.0GPa and 135.5Gpa to 8.0Gpa and 106.6GPa respectively, as the RF power increases from 500W to 700W. We also use the oscilloscope with a high voltage probe to testing the relationship between the RF conceited bias and the RF power, the depression at the RF glow discharge process in the pure argon gas, acetylene and their mixture gas. It is found that the RF negative self-bias voltage, increasing with RF power and decreasing with working pressure, is a linear function of the square root of the RF power divided by the working pressure for all the gases used. All indicate that the higher RF power gives rise to a higher RF negative self-bias voltage and therefore a higher ion energy, which enhances the effect of ion bombardment and leads to a graphitization of a-C:H films and a reduction of the hydrogen content.The above analysis shows that the hardness of the films we got by using Pulse-PECVD technical is higher than the carbon films prepared by RF-PECVD. We will get the better performances of the DLC films and realize industrial applications, if the deposition conditions are optimized such as increasing substrate bias voltage and the acetylene flow.