Hydrocarbon formation in the reaction of atomic hydrogen with pyrolytic graphite and the synergistic effect of argon ion bombardment

Chemical sputtering of carbon films by argon ions and molecular oxygen at cryogenic temperatures

“…The observed synergism recalls another synergism in a-C:H erosion, namely, that between ion bombardment and atomic hydrogen [22,23,[28][29][30]. In this case, the proposed explanation [23] was that ion bombardment creates dangling bonds at and below the surface which become passivated by H. By repeated such events hydrocarbon molecules are formed which leave the surface.…”

Temperature dependence of the chemical sputtering of amorphous hydrogenated carbon films by hydrogen

“…They found a significantly enhanced erosion yield compared with the sum of the individual processes -physical sputtering due to ion bombardment and chemical erosion due to hydrogen atoms. Such a synergistic effect, i.e., that the yield of the combined interaction of ions and neutrals hydrogen atoms is higher than the sum of the yields of the individual processes, has been found earlier by Vietzke et al for the combined bombardment of graphite with Ar + (5 keV) + H 0 [11,12] and by Davis et al for H + (50 eV to 3 keV) + H 0 [13]. Erosion due to the combined interaction of reactive neutrals and energetic ions was named chemical sputtering [5,[7][8][9][10].…”

“…On the other hand, a-C:H films represent a model system for the chemical sputtering of graphite by hydrogen ions and the study of such films helps to better understand the involved basic processes. The bulk of the studies devoted to a-C:H films addressed the measurement of the production yield of certain hydrocarbon species by mass spectrometry [11][12][13][14][15][16][17][18][19][20]. Although such experiments deliver very valuable information on the erosion process and the produced species, they do not necessarily determine the total erosion yield.…”

Synergistic etch rates during low-energetic plasma etching of hydrogenated amorphous carbon

“…51 The erosion yield (10 À3 -10 1 ) depends furthermore on the ion energy and incident ion flux and, all else being equal, is higher for a-C:H than for graphite. 1,10,14,16,18,40,45,47,48 The fourth and last mechanism explained here is swift chemical sputtering, which first came to light via numerical modelling of very high hydrogen fluxes (up to 10 29 m À2 s À1 ) incident on an a-C:H surface. [52][53][54][55] An incident hydrogen radical enters the space occupied by a carbon-carbon bond.…”

“…33,36,44 Weakly bonded hydrocarbons -either created after a chemical erosion reaction or (re-)deposited on the a-C:H surface -have an E a on the order of 0.6 eV for thermal desorption. 45,46 Breaking the C network -CH 3 bond is thus the rate-limiting step in chemical erosion. 35 The erosion can moreover be enhanced by simultaneously irradiating the surface with ions (10 16 À 10 24 m À2 s À1 ).…”