NON-THERMAL ABLATION OF GRAPHITE BY ULTRASHORT PULSED FS-LASER RADIATION

摘要

We will present results of studies on a novel fs-laserrninduced ablation mechanism, which in literature isrndenoted as ?athermal“ or ?non-thermal“ and includesrnno melting or evaporation processes. This non-thermalrnablation process is capable for solids where the atomicrnbond strength normal to the surface is significantlyrndifferent to those in lateral direction. One example forrnsuch a solid is given by graphite. In graphite thernCarbon atoms of a single graphene layer are bondrncovalently and thus exhibiting a bond strength of 4 eVrnper atom. In contrast, the interlayer bond strengthrnnormal to the surface results of the more than twornorders of magnitude weaker Van-der-Waalsinteraction.rnWithout influencing the strong layerrninternal sp~2-bonds this ablation process only breaks thernweak van-der-Waals bonds between the layersrnresulting in a spalation dynamic of the topmost intactrngraphene layers from the surface of the highly orientedrnpyrolytic graphite target. Maintaining the internal sp~2rncrystalline structure of the ablated graphene layers thisrnnon-thermal ablation process is feasible to transfer thinrnlayer of sandwich structured solids on variousrnsubstrates, conserving their mechanical and electronicrnproperties.