Hydrogen permeation barrier performance characterization of vapor deposited amorphous aluminum oxide films using coloration of tungsten oxide

Low hydrogen diffusivity and solubility of aluminum oxide make a vapor deposited aluminum oxide (Al2O3) film an anticipated hydrogen permeation barrier coating. In this paper, amorphous Al2O3 film was deposited using filtered vacuum arc method. As a substrate, vapor deposited amorphous tungsten oxide (WO3) film was used in order to characterize hydrogen permeation barrier performance of the Al2O3 film utilizing coloration of WO3 when it forms HxWO3. The samples were exposed to the flux and angular quantified atomic hydrogen beam, and the degree of coloration was characterized by visible to near infrared range transmission spectroscopy. Using this method, a half-micron thick amorphous Al2O3 film reducing atomic hydrogen reaching the underlying WO3 film to 3×10−4 was measured. Furthermore, Al2O3 film as thin as 20 nm showed atomic hydrogen reduction of 4×10−3. The results indicate effectiveness of thin vapor deposited Al2O3 film as a permeation barrier against atomic hydrogen.