This paper concerns with temperature dependence of tungsten (W) sputtering
by carbon (C). Weight loss measurements of W samples during sputtering by 2
.4 keV C ions at different temperatures in the range between 300 and 1000 I
t showed a strong temperature dependence. At a certain fluence, which depen
ds on the temperature, the probe's weight starts to increase again. This is
due to C enrichment in the surface during ion bombardment, which eventuall
y leads to the formation of a pure C surface. This C film then shields the
underlying W from further sputtering and further growth of this film increa
ses the probe's weight. The growth of this him depends critically on the di
ffusion of C into the W bulk material since this removes C from the surface
and thereby increases the W concentration and W erosion. This in turn resu
lts in an increased reflection of the incoming C ions. These two coupled me
chanisms hinder the growth of the C film with the diffusion accounting for
the temperature dependence of the weight loss. To verify this model, C dept
h profiles in W were determined by means of Rutherford backscattering (RBS)
with He ions. To increase sensitivity, the increased cross-section at 5715
keV was used. Analysis of depth profiles measured in the temperature range
between 300 and 1000 It show that relevant diffusion processes appear at a
pproximately 800 K, By performing Boltzmann Matano analysis on the measured
depth profiles, a concentration dependant diffusion coefficient for C diff
usion in W was deduced. The weight loss measurements were simulated using a
combination of the Monte Carlo program TRIDYN and the diffusion code PIDAT
. (C) 2001 Elsevier Science B.V. All rights reserved.