SURFACE MODIFICATIONS AND EROSION YIELDS OF SILICON AND TITANIUM-DOPED GRAPHITES DUE TO LOW-ENERGY D+ BOMBARDMENT

Influences of low energy D+ ion bombardment and target temperature on surface topography, surface concentration and erosion yield of carbon based binary compounds were investigated. The samples contained 10 at. % Si acid 10 at.% Ti, respectively. The surface concentration was dete rmined in situ by Auger electron spectroscopy and the topography ex si tu by scanning electron microscopy. During low energy D+ bombardment a pronounced conelike surface developed with silicon respective titaniu m rich 'caps' protecting the underlaying carbon rich shafts from erosi on. The average dopant surface concentration was up to 7 X the bulk co ncentration. The erosion mechanism was determined by surface concentra tion and chemical state of the surface: At high temperatures carbidic bindings dominated, while at room temperature a mixture of graphite an d carbide covered the surface.