Characterization of the electronic and geometric structures of aluminas using X-ray photoelectron spectroscopy, Auger electron spectroscopy, electron energy loss spectroscopy, and low energy electron diffraction.

摘要

The electronic and geometric structures of aluminas have been studied with X-ray photoelectron spectroscopy (XPS), Auger electron spectroscopy (AES), electron energy loss spectroscopy (ELS), and low-energy electron diffraction (LEED). The first part of this work is a study of the charging and the binding energy reference problem for insulators in XPS. The effects of the low energy flood gun on the spectra are shown to depend on the thickness of the oxide. The discrepancy in the reported apparent binding energy of Al(2p) of aluminas, 74.5 eV for {dollar}gamma{dollar}-alumina powder and 76.3 eV for thin {dollar}gamma{dollar}-alumina film on Al, is accounted for by the difference in the reference level used and by the use of the same value for C(1s) of adventitious carbon on both metal and insulator surfaces.; The second part of this work is an XPS study of bulk aluminas. As the structure of alumina changes from {dollar}gamma{dollar}-alumina to {dollar}alpha{dollar}-alumina, the intensity at the center of the upper valence band decreases, while that at the bottom of both the upper valence band and the lower valence band increases. Hydroxyl groups in anodic alumina cause a 0.6 eV increase in the apparent binding energies of O(2s) and O(1s), and a diffuse shoulder on the high kinetic energy side of KL{dollar}sb{lcub}23{rcub}{dollar}L{dollar}sb{lcub}23{rcub}{dollar} as well as an 1.8 eV increase in the separation between KL{dollar}sb{lcub}23{rcub}{dollar}L{dollar}sb{lcub}23{rcub}{dollar} and KL{dollar}sb1{dollar}L{dollar}sb{lcub}23{rcub}{dollar} in O(KLL). The Al Auger parameter of {dollar}alpha{dollar}-alumina is 0.4 eV higher than that of {dollar}gamma{dollar}-alumina and 1.3 eV higher than that of anodic alumina.; The third part of the work is a study of the initial oxidation of the A1(111) surface at 450C and 5 x 410{dollar}sp{lcub}-7{rcub}{dollar} torr. A p(4 x 1) and a p(1 x 1) LEED pattern are observed at 50L. A (4{dollar}surd{dollar}3 x 4{dollar}surd{dollar}3)-R30 pattern, a subset of the p(1 x 1(, shows up at 100L. After 5KL exposure, only the p(1 x 1) and its subset remain. In the AES interatomic region at 50L the spectrum still looks closer to that of the clean surface; while at 75L it clearly shows the presence of the oxide.