Chemical alteration of thin alumina films on aluminum during hydrogen-atom exposures

• Published in: Applied surface science 1998-04, Vol.126 (3), p.235-240
• Main Authors: Epling, William S, Mount, Charles K, Hoflund, Gar B, Young, Vaneica Y
• Format: Article
• Language: English
• Subjects: Alumina; Analytical chemistry; Chemistry; Cross-disciplinary physics: materials science; rheology; Electron spectroscopy (x-ray photoelectron (XPS), Auger electron spectroscopy(AES), etc.); Exact sciences and technology; Foil; H-atom; Hot-rolled; Materials science; Physics; Re-oxidized; Spectrometric and optical methods; Surface treatments
• ISSN: 0169-4332; 1873-5584
• DOI: 10.1016/S0169-4332(97)00696-X

Hot-rolled and partially oxidized Al foil surfaces were examined before and after H-atom exposures using X-ray photoelectron spectroscopy (XPS) and ion scattering spectroscopy (ISS) to monitor the changes which occur at the sample surfaces. The near-surface region of the native oxide of the hot-rolled Al foil contains primarily C and O. Cl and Ca contamination also are present at the outermost atomic layer according to ISS. H-atom exposures reduce the amount of carbonates and hydrocarbons but causes an enrichment of sulfur in the outermost layer of the foil. The O-to-Al ratio is reduced, and the AlO x species initially present is converted to Al 2O 3. After sputtering the Al foil to remove the Cl, C, and Ca contaminants, the Al was exposed to oxygen at 10 −7 Torr for 10 min. The near-surface region of this re-oxidized surface contains both Al metal and Al 2O 3. Exposing this partially oxidized surface to H-atoms produces a chemically-induced driving force which causes subsurface O to migrate toward the surface of the foil. This results in an increase of the Al 2O 3 concentration at the sample surface. These results suggest that the thickness of Al oxide layers may be controlled using H-atom exposures. Furthermore, the amounts of carbon contamination can be decreased and possibly eliminated without reducing the alumina.