Overview on the effects of dopants on chemical erosion and RES of carbon-based materials

For carbon-based materials physical sputtering, chemical erosion, and radia tion enhanced sublimation (RES) are the primary erosion processes due to io n impact. For Ii impact the influence of dopants (e.g. B, Si, Ti) on the ra diation enhanced chemical erosion (Y-therm) at temperatures around 800 K is discussed. For B doping the reduction of the erosion yield could be descri bed by a reduction of the activation energy for H release. At low surface t emperatures and low H ion energies a reduction of the chemical enhanced phy sical sputtering yield (Y-surf) due to dopants is observed and discussed. I t is unclear if the reduction is just caused by modification of the surface composition due to preferential erosion of carbon. The surface composition and the erosion yield depend on ion fluence, dopant distribution, producti on procedure and operational history of the target. On atomic scale the dop ant distribution causes changes in the chemical bonds and reactions and, th erefore, in the chemistry necessary for both chemical erosion regimes (Y-su rf, Y-therm) Also, the basic processes of RES - interstitial production, mi gration, recombination, and thermal desorption - could be influenced. At hi gh temperatures, at which RES dominates, the stability of the material and sublimation of the dopant has to be taken into account.