THE HYDROGEN INVENTORY IN PLASMA EXPOSED GRAPHITE SURFACES

摘要

The trapping of hydrogen in graphite was investigated during exposure to an rf-discharge. The target placed in the wall of the rf-reactor was investigated in-situ by ion beam analysis. The hydrogen inventory was found to be twice as high as expected from ion beam implantation experiments in the similar energy range less than or equal to 200 eV, Also an enhanced ion induced desorption by the energetic analyzing beam was observed. This leads to the conclusion that a buildup of a hydrogen rich C:H-layer is formed by the simultaneous impact of thermal and energetic (less than or equal to 200 eV) hydrogen, A model is presented which explains the formation of the C:H-layer by a stitching process of methyl radicals forming on the surface, Time resolved trapping measurements were performed to test for a transient uptake of hydrogen during plasma exposure. No such phenomenon could be detected below 600 K. Also the supposition that metallic impurities are responsible for a dynamic inventory at room temperature could be disproved. [References: 46]