Helium accumulation in tungsten layers deposited in Ar-He magnetron discharge

Abstract W-He co-deposition was studied by means of in-vacuo thermal desorption spectroscopy. W-He co-deposited layers were produced at substrate temperatures varied from 400 K to 800 K with a 50 K temperature step. It was found that the He content decreases from ∼1.7 at. % at 400 K to ∼0.17 at. % at 750 K. At 800 K, an increase in the He content was observed, that should be caused by significant changes in the film structure. Helium TDS spectra had two main peaks with maxima in the 500-600 K range and at ∼960 K; the peaks observed are similar to those previously seen for He ion implantation in W. Several scaling expressions are proposed for He/W vs. T.