Retention and re-emission of deuterium implanted into tungsten monocarbide

The retention of deuterium in tungsten monocarbide on graphite, implanted with 5 keV D2- ion beams up to saturation at room temperature and the re-emission of deuterium from tungsten monocarbide by post thermal annealings have been studied by means of the elastic recoil detection (ERD) technique. It is found that the steady state concentration of retained deuterium is 1.7 x 1022 cm-3 at room temperature, which decreases to 1.4 x 1022 cm-3 due to spontaneous re-emission in 5 h of terminating the implantation. It is also found on isothermal annealing at temperatures of 70 C, 100 C, 150 C, 200 C and 250 C that the concentration of retained deuterium decreases rapidly in the beginning and hereafter very gradually with increasing annealing time. The re-emission profiles have been analysed taking into account thermal detrapping (Σd), retrapping (ΣT), local molecular recombination (K1) between movable deuterium atoms. It is determined that the activation energy of the effective molecular recombination rate constant (K1/C0)(Σd/ΣT)2 is 0.47 eV, where C0 is the trap density and that the activation energy of the thermal detrapping rate constant Σd is 0.20 eV. (orig.)