Fabrication and Hydrogen Permeation Properties of Epitaxial Er2O3 Films Revealed by Nuclear Reaction Analysis

In order to evaluate the potential of erbium oxide films in applications such as hydrogen (H) permeation barriers, we fabricated high-quality Er2O3 thin films by ion beam sputter deposition on Si(100) as an epitaxial substrate. The physical structures of the thin films were characterized by scanning X-ray diffraction, and the process of hydrogen permeation through the Er2O3 films upon annealing in H-2 was elucidated by H depth profiling with nuclear reaction analysis. The results show that quasi-single-crystalline Er2O3(110) thin films can be produced that feature a hydrogen solubility, diffusivity, and permeability at 873 K of (1.1 +/- 0.2) x 10(2) mol m(-3), (7.2 +/- 1.4) x 10(-22) m(2) s(-1), and (3.8 +/- 1.5) X 10(-22) mol Pa-1/2 m(-1) s(-1), respectively. The remaining difference in hydrogen permeability between our quasi-single-crystalline Er2O3(110) thin films and that expected for ideal bulk Er2O3 attests to the negative role of residual defects (e.g., pores) that exist in the thin films.