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Hydrogen permeability in thermally grown films of SiO2 on silicon substrates.

We describe a technique for measuring the room-temperature permeability of molecular hydrogen through thin films of thermally grown SiO 2 on Si substrates. We have used this technique to determine the H 2 permeability in oxide films ranging from 161 to 1082 A in thickness. We find that the permeability decreases as the film thickness decreases. Even for the thickest films studied, the permeability is only about 8% of the value characteristic of bulk SiO 2 . We attribute the permeability differences to a gradient in the density of the thermal oxide