Interaction of H(D) atoms with surfaces of glassy carbon:adsorption,adstration,and etching

摘要

The interaction of thermal (2000K)H and D withglassy carbon (GC) surfaces wasinvestigated in ultrahigh vacuum environmental using thermal desorption and reaction an d reaction kinetics mass spectroscopy.Virgin GC surfaces(not previously subjected to stationary etching by H atoms) exhibit a remarkably low reactivity withrespect to adsorption of D.The saturaton coverage of D on GC is about a factor of ten smaller than on (0001) graphite surfaces (HOPG or natura signle crystal).Thermal desorption spectra indicate that D atoms on virgin GC surfaces are adsorbed on distorted graphite basal planes,i.e.the recombinative desorption features of D onGC between 400 and 600 K are broadened as compare dt those measured on graphite.Upon heating of D-covered efficient aroudn 600 K,as was previously observed on other carbon materials,a-C:H thin films and graphite,and as expected from the etching mechanism on C substrtes.GC surfaces repeatedly etched by H exhibit an increasing density of C atoms located at edge sites which are capable to adsorb D via formation of Sp~n C-D bonds.D from these sites desorbs recombinatively around 830 K and competitive desorption of C_2 by H exhibitsthe same phenomenology as on graphite:Eley-Rideal mechanism and large abstraction cross-section at small D coverages.