Hydrogen storage in the bubbles formed by high-flux ion implantation in thin Al films

The storage of implanted hydrogen in 2-5 μm thick Al films on stainless steel substrates was investigated in this work. Plasma immersion 1 keV H2+ ion implantation was used to load hydrogen into the Al film. The correlation between the effusion of the implanted hydrogen and the evolution of surface morphology was studied by thermal desorption spectroscopy and scanning electron microscopy. It has been found that as-implanted hydrogen at temperatures below 320 K is associated with defects and is chemically bonded at the grain boundaries of nanocrystallites. At higher temperatures, the released hydrogen is accommodated in bubbles. The major part of hydrogen effuses at ∼630 K and the effusion process is controlled by the migration of hydrogen through the surface oxide layer.