Oxide films were generated by substrate oxidation and by plasma or physical vapor deposition. The films which were grown by oxidation were crystalline, and the others were amorphous. The defect structures of the films were studied by using positron spectroscopic techniques. The positron lifetimes, and Doppler broadening of the γ photons which were generated by their annihilation, were measured as functions of the energy with which they were injected. The densities and sizes of the defects were thus determined as functions of the depth from the outer surface of the film. The films which were generated by oxidation had high densities of open-volume defects which consisted mainly of a few aggregated vacancies. In the outer regions of the films, the structure of the defect did not depend upon the substrate composition. The positron lifetime measurements, and the S and W parameters which were extracted from the Doppler broadening spectra, revealed uniform distributions of defects in the crystalline oxide films which were grown on NiAl substrates, but the associated data indicated intermediate layers of higher defect content at the film/substrate interfaces of oxides which had been grown on FeAl substrates. The amorphous films which were generated by plasma and physical vapor deposition had much larger open-volume defects, which caused the average lifetimes of the injected positrons to be significantly longer. The plasma-deposited film contained a high density of large cavities.

Microstructure of Thermally Grown and Deposited Alumina Films Probed with Positrons. B.Somieski, L.D.Hulett, J.Xu, B.A.Pint, P.F.Tortorelli, B.Nielsen, P.Asoka-Kumar, R.Suzuki, T.Ohdaira: Physical Review B, 1999, 59[10], 6675-88