Free-standing diamond films prepared by a dc-plasma method above the ethylene glycol solution

Free-standing diamond films were prepared using a plasma chemical vapor deposition method above the liquid surface through two routes. Diamond was deposited on the surface of a tungsten anode under a dc-plasma regime. The electric field near the anode surface was flattened by placing a sub-electrode and it brought uniform film deposition. The growth rate was 5 μm h− 1 and the thickness increased with the deposition time up to 12 μm. A free-standing film removed from the tungsten anode showed translucency. A glassy carbon layer with a thickness of 100 nm existed between the diamond film and the anode surface, and it partly remained on the back side of the removed diamond film. Under a plasma-jet regime, diamond was deposited on a silicon substrate brown with a plasma jet expelled from a nozzle exit. A high growth rate of 100 μm h− 1 was attained at the maximum with increasing discharge power and carbon concentration, but the thickness profile was quite uneven. The removed film was elliptical and was larger than the nozzle size. A 3C–SiC layer was formed on the back side of the removed film.