Overview on the Effects of Dopants on Chemical Erosion and RES of Carbon-Based Materials

Abstract

For carbon-based materials physical sputtering, chemical erosion, and radiation enhanced sublimation (RES) are the primary erosion processes due to ion impact. For H impact the influence of dopants (e.g. B, Si, Ti) on the radiation enhanced chemical erosion (Ytherm) at temperatures around 800 K is discussed. For B doping the reduction of the erosion yield could be described by a reduction of the activation energy for H release. At low surface temperatures and low H ion energies a reduction of the chemical enhanced physical sputtering yield (Ysurf) due to dopants is observed and discussed. It 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, production procedure and operational history of the target. On atomic scale the dopant distribution causes changes in the chemical bonds and reactions and, therefore, in the chemistry necessary for both chemical erosion regimes (Ysurf, Ytherm). Also, the basic processes of RES – interstitial production, migration, recombination, and thermal desorption – could be influenced. At high temperatures, at which RES dominates, the stability of the material and sublimation of the dopant has to be taken into account.