Amorphous carbon coating mixed with nano-diamonds

A low temperature plasma process for alternately depositing a diamond layer and an amorphous-carbon layer, i.e. DLC (diamond like carbon), on a same substrate was developed. In order to make both DLC and diamond coexist on a same substrate, we developed a method to form diamond at lower temperature than 500 K, since at a higher temperature DLC is easily crystallized and changed to graphite. We constructed an apparatus that had two types of plasma generators for radio frequency and microwave. The substrate temperature can be kept at 473 K during depositions for both DLC and diamond. Laser-Raman spectrometry and transmission electron microscope observation showed existence of both DLC and diamond in the coated layers. The coating has excellent mechanical properties, such as higher hardness than DLC and very low friction comparable to DLC.