Plasma hydrogenation of MgAl thin films and H2 effusion

The accommodation of hydrogen in 4-5 μm thick MgAl films deposited by dc magnetron sputtering on (1 1 1) oriented Si substrate and submitted to hydrogenation using 2 keV H2+ plasma immersion ion implantation technique at 473 K and 10 Pa pressure in 90% H2+10% Ar and 90% H2+10% O2 working gas plasmas was investigated. Morphological and structural properties were studied by scanning electron microscopy and X-ray diffraction. Glow discharge optical emission spectroscopy was used for the analysis of hydrogen distribution in hydrogenated films. Thermal desorption spectroscopy analysis revealed the hydrogen effusion kinetics. It was shown that the surface oxide barrier layer plays an important role on the hydrogenation efficiency and controls the H2 thermal effusion. The maximum efficiency of hydrogenation was obtained in H2+O2 plasma when incident hydrogen ions pass the surface oxide barrier layer without destroying it. The Ar sputtering during hydrogenation in H2+Ar plasma erodes the surface barrier layer and decreases the retention probability of the implanted hydrogen atoms.