Fluorination of graphite surface using electron cyclotron resonance plasma

Fluorinated carbon, which has low surface energy and better thermal stability, is applicable to water repellents, lubricants and battery cathods. In the present paper, we have examined the modification technology of CF4 electron cyclotron resonance (ECR) plasma treatment with rf-induced negative self bias voltage on graphite substrates in order to modify the surface of graphite to fluorinated structure. Especially with the purpose of preparating the durable fluorinated surface, we have investigated the treatment process factors, and compared the initial property of the modified surface and the property change with the elapse of time. The larger contact angle value of water than that of PTFE certified that the surface of graphite was modified. A further good result has been shown that there occurs only a slight change of the repelling property with the elapse of time. X-ray photoelectron spectroscopy (XPS) result indicated that the higher the rf-induced negative self bias voltage was, the larger the peak area ratios of CF2 and CF3 species to C-1s spectrum became. It is considerd that the fluorinating reaction was accelerated by the ion bombardment due to rf-induced bias voltage, so that CF2 and CF3 species were formed in the deeper region from the surface. As mentioned above, it was found that applying the rf-induced negative self bias voltage on graphite substrates was an important factor to give the modified surface durability.