Ion beam analysis of deuterium-implanted Al2O3 and tungsten

Single crystal tungsten and Al2O3 (sapphire), and polycrystalline WESGO-995 Al2O3 samples were implanted with 20-30 keV deuterium at 300-500 K. The deuterium distributions were determined using He-3-D nuclear reaction analysis, at 300-800 K. The results indicated that considerable diffusion occurred both during the implantations and during the subsequent analysis. Modelling the data indicates effective (radiation-enhanced) diffusivities as high as 10(-16) m(2)/s in Al2O3, compared to a thermal diffusivity similar to 10(-41) m(2)/s at 300 K [J.D. Fowler, D. Chandra, T.S. Elliman, A.W. Payne, K. Verghese, J. Am. Ceram. Soc. 60 (1977) 155.]. The modelling also suggests that most of the implanted deuterium was released at the surface, although a significant fraction diffuses to depths greater than the expected ion range. In tungsten, implanted deuterium is trapped at defects that appear to be mobile at 300 K, enabling the deuterium distribution to extend much deeper than the ion range. At higher temperatures the trap energy appears to increase with time. Modelling the data indicates little deuterium release through the front surface, i.e. most diffused deeper into the bulk of the sample. (C) 1998 Elsevier Science B.V. All rights reserved.