Deuterium and Helium Release and Microstructure of Tungsten Deposition Layers Formed by RF Plasma Sputtering

Hydrogen incorporation in tungsten deposits growing by deuterium plasma sputtering

“…As a tendency, the density does not seem to depend on the growth rate and the substrate temperature but seems to depend on the gas pressure. The samples formed at 2 Pa indicated the highest density but it was much smaller than a bulk density of tungsten, 19.3 g/cm 3 .…”

“…Therefore, hydrogen behavior in tungsten deposits is not necessarily the same as that in tungsten bulk. In order to investigate basic behaviors of hydrogen isotopes in tungsten deposits, the present authors have produced tungsten deposit samples by an RF plasma sputtering device [1][2][3][4]. It have been reported in previous papers that the produced tungsten deposits contain a numerous bubbles and retain a large amount of hydrogen isotopes [3].…”

Effect of oxygen on hydrogen retention in W deposition layers formed by hydrogen RF plasma

“…The other reason is that hydrogen solubility in tungsten bulk is a quite low [2]. However, it has been found by the present authors that tungsten deposition layers formed by hydrogen plasma sputtering can retain a large amount of hydrogen [3][4][5]. In some cases, these deposition layers contained oxygen in addition to hydrogen.…”

“…In conditions shown as shaded portion, on the other hand, tungsten oxide is reduced with hydrogen. It has been found that 24 at% of oxygen was detected in the W layer formed at a temperature of 70 • C but no oxygen was detected in that formed at a temperature of 140 • C [5]. In our recent study, it seemed that when the substrate temperature was higher than about 100 • C, a large amount of oxygen was not retained in a W layer.…”

“…A capacitively coupled RF plasma device installed parallel-electrode and the experimental procedure have been mentioned in previous papers [3]. The approximate plasma parameters have been reported for some conditions by Langmuir probe method [5]. The ion flux to the substrate located on the ground electrode was 10 19 -10 20 m −2 s −1 and the electron density was 10 16 -10 17 m −3 at RF powers of 50-200 W, respectively.…”