Interaction of deuterium gas with dry SiO2 on Si: An ion-beam study

The interaction of deuterium gas (D2) with nominally dry SiO2 on Si was characterized in the temperature range 100–1000 °C using high-sensitivity nuclear-reaction analysis for D. Two trapped configurations were distinguished: one, hypothesized to involve Si–D bonding, produced D uptake at 300 °C and above followed by release at 600 °C; the other, identified as O–H, formed readily at 100 °C and dissociated at about 800 °C. Retained D in the 0.5-μm oxide layer was present at areal densities of about 1014 atoms/cm2 or less, and it was distributed approximately uniformly except for a small surface peak. Prior irradiation with high-energy He ions increased the D uptake by two orders of magnitude through, it is believed, the same trapping mechanisms discussed above. The data on uptake and release were semiquantitatively described by a fitted mathematical model, from which effective activation energies for trapping and detrapping were obtained.