Techniques have been developed for obtaining reproducible lattice phonon spectra of barrier aluminum oxide anodic films. Changes in the lattice phonon spectrum as a result of 15-keV proton bombardment are interpreted in terms of the formation of Al-OH bonds. Polarization spectra of stripped and unstripped aluminum oxide films confirm the findings of Vedder and Vermilyea, particularly with respect to the origin of the 960 cm−1 band. The close similarity in the observed and calculated band shapes (using the theory of Berreman) leave little doubt that the 960 cm−1 absorption is due to a longitudinal optic mode of the aluminum oxide lattice.
VedderW. and VermilyeaD. A., Trans. Faraday Soc.65, 56 (1969).
3.
MaelandA. J.RittenhouseR.LaharW., and RomanoR. V., Thin Solid Films21, 67 (1974).
4.
BerremanD. W., Phys. Rev.130, 2193 (1963); for additional discussions of photon-phonon interactions in thin films see Fuchs et al., Phys. Rev. 140, A2076 (1965); ibid. 144, 495 (1966); 150, 573 (1966); 150, 589 (1966); RuppinR., Phys. Rev.9B, 1908 (1974); BalkanskiM. and LeToullecR., in Optical Properties of Dielectric Films, AxelrodN. N., Ed. (The Electrochemical Society, Inc., New York, 1968).
5.
BarkerA. S., Phys. Rev.132, 1474 (1963).
6.
GruenD. M.WrightR. B.SheftI., and McBethR. L., to be published.
7.
A more complete review of the anodization of aluminum metal is given by YoungL., Anodic Oxide Films (Academic Press, New York, 1961), Chaps. 16 and 17.
8.
BurghersClaassen, and Zernike, Z. Phys.74, 593 (1932) determined the density of Al2O3 films anodized in boric acid to be 3.10 ± 0.05 g/cm3. The density of anodized films is, however, very dependent on conditions of electrolysis.
