Trapping and release of deuterium in helium-induced tungsten fuzz at low temperature

The release of deuterium (D) atoms from a nanostructure ‘fuzz’ tungsten (W) after a sequential plasma irradiation of helium (He) and D was explored. Thermal desorption spectroscopy revealed that more than 60% of total D amount was already released at $>$423 K. A sophisticated measurement with an aberration-corrected scanning TEM combined with electron energy-loss spectrometer (STEM-EELS) directly showed the trapping of D atoms into He bubbles after the plasma irradiation and the release of D from the He bubbles at elevated temperature at 423 K. The He bubbles containing D were characterized by (i) relatively large volume and (ii) small He energy-loss shift below 2 eV. It is suggested that the shifts in the energy-loss peaks of He and D could be used as indicators of D absorption within He bubbles.