Erosion of diamond films and graphite in oxygen plasma

The nature and rates of erosion of diamond, graphite, and diamond-like carbon (DLC) films exposed to oxygen plasmas were evaluated by comparison of surface morphological changes and weight losses. The RF plasma oxidation at ambient temperature caused severe etching of graphite and DLC specimens, while causing only minor damage to diamond film surfaces. The results suggest that erosion by low energy ions is very selective to the sp² and sp states compared to the sp³ state of carbon. The selectivity of etching by oxygen plasma is significant, as compared to what has been reported for hydrogen in atomic and ionic states, or for oxidation at elevated temperatures in molecular oxygen. These observations have significant implications to the synthesis of diamond films by chemical vapor deposition (CVD) as well as to the application of diamond film coatings on graphite or other substrates for protection against energetic atomic oxygen prevailing in the low earth orbits (LEO).