Plasma hydrogenation of MgAl thin films and H-2 effusion

Abstract

The accommodation of hydrogen in 4-5 mu n thick MgAl films deposited by dc magnetron sputtering on (1 1 1) oriented Si substrate and submitted to hydrogenation using 2 keV H-2(+) plasma immersion ion implantation technique at 473 K and 101 Pa pressure in 90% H-2+10% Ar and 90% H-2+10% O-2 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 H-2 thermal effusion. The maximum efficiency of hydrogenation was obtained in H-2+O-2 plasma when incident hydrogen ions pass the surface oxide barrier layer without destroying it. The Ar sputtering during hydrogenation in H-2 + Ar plasma erodes the surface barrier layer and decreases the retention probability of the implanted hydrogen atoms. (c) 2005 Elsevier Ltd. All rights reserved.