Abstract
Diamond films are deposited on an aluminum substrate under a constant high discharge current (Id=700 mA) and a methane concentration of about 2% by DC plasma CVD, and their structural characteristics resulting from the difference in substrate temperature (Ts: 140–480°C) are investigated. Many diamond particles with an average size of 0.3 µm and having a clear crystal habit are formed at Ts about 480°C. When Ts is decreased, the deposited films tend to contain hydrogenated amorphous components as well as amorphous carbon phases. The films deposited at extremely low Ts, such as 140°C, are composed of submicron grains like pebbles, in which nanocrystalline diamond crystals and amorphous phases having C–C and C–H bonds aggregate to form these submicron grains. It has been found that diamond films with different grain morphology are deposited on the Al substrate.