Retention and enrichment of tungsten-containing carbon films under deuterium beam impact

Retention and enrichment of a model system for mixed layers, tungsten-containing carbon films (a-C:W), were investigated with respect to the interaction with D ions. a-C:W was exposed to a mass-separated, mono-energetic D beam (200 eV/D, 1.2 × 1015 D cm−2 s−1). The W concentration in the films (0–7.5 at.%), the specimen temperature during D beam exposure (300–1300 K) and the fluence (Φ) of incident D (1015–1020 D cm−2) were varied. Analysis of retention and enrichment were performed by nuclear reaction analysis and Rutherford backscattering spectrometry, respectively. At 300 K and fluences up to 1019 D cm−2, the increase of the D inventory with fluence in a-C:W cannot be distinguished from a-C and pyrolytic graphite, e.g., above ∼1017 D cm−2 the D inventory increases with fluence according to Φx (x = 0.1). Above a fluence of 1019 D cm−2, however, the D inventory depends strongly on the W concentration. At a fluence of 1020 D cm−2 the D inventory is increased to the 1.5-fold of the D inventory of pyrolytic graphite for 1% and 2.5% a-C:W and it is decreased to the half value of the D inventory of pyrolytic graphite for 7.5% a-C:W. At temperatures above 300 K, following trends are observed: With increasing temperature, the D inventory increases more strongly with fluence and D reaches depths far beyond the width of the ion range. However, the D inventory does not increase with fluence according to Φx, especially at fluences above 1019 D cm−2.