Effect of helium presence on tungsten-deuterium co-deposited films

Co-deposited W-D, W-He, and mixed W-D-He films 250 nm thick were investigated. The films were obtained by magnetron sputtering of W in Ar:D-2:He 1:1:0, 1:0:1, 1:1:0.05, and 1:1:0.2, gas mixtures and at deposition temperatures of similar to 350 K, 500 K, and 800 K. The films were studied by thermal desorption spectroscopy (TDS) with T-max = 2200 K using threshold ionization mass spectrometry to separate D-2 and He signals. It was found that films obtained in gas mixtures with mixed He-D-2 atmospheres contained less total gas atoms than films deposited in pure D-2 or He atmospheres. It was found that in mixed W-D-He films, He trapping with high binding energies (T-des > 1500 K) is strongly mitigated.