Erosion of carbon deposition layer by hydrogen RF plasma

A carbon deposition layer was formed by sputtering method in hydrogen RF plasma at an RF power of 150 W and then eroded in a plasma at an RF power of 250 W. The sheath bias between plasma and the carbon deposition layer was measured to be about 10 V by Langmuir probe method. The erosion yield (C/ion) of carbon deposition layer was determined to be 0.31, which is one order of magnitude larger than that of isotropic graphite, 0.026. It was found that the plasma facing surface of the eroded carbon deposition layer became mesh-like and the inside of the layer became more porous. The atomic ratio of hydrogen to carbon (H/C) in the carbon deposition layer eroded for more than 6 h obviously decreased as compared to the initial value.