Application of TEM extended electron energy loss fine structure to the study of aluminium oxide films

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Abstract
The technique of extended electron energy loss fine structure (EXELFS) using an electron energy loss spectrometer fitted to a transmission electron microscope (TEM) has been applied to a study of the structure of the thin layer of amorphous alumina (Al2O3) which is formed on aluminium by anodic oxidation in neutral sodium tartrate solution. The EXELFS spectrum above the oxygen K-edge gives an Al-O bond length of 1–89 A, which is in good agreement with a previous measurement obtained from the electron-yield surface extended X-ray absorption fine structure (EXAFS) above the aluminium K-edge. The Al-O bond length derived from EXELFS measurements for the oxide film after crystallization in the electron beam shows that the structure of the crystalline phase is consistent with the reported structure of γ-alumina. Electron-yield surface EXAFS is generally a broad-beam technique, more applicable to in aitn studies of surface films. TEM EXELFS requires the films to be detached from their substrates, but the electron beam probes the specimen with high spatial resolution. The relative merits of these two techniques for structural studies of thin oxide layers are discussed.