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Electronic Structure of a-Al2O3,
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R. H. French, H. Müllejans, D. J.
Jones, "Optical Properties of Aluminum Oxide: Determined from Vacuum
Ultraviolet and Electron Energy Loss Spectroscopies", Journal of the
American Ceramic Society, 81, 10, 2549-57, (1998). |
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S. Loughin, R. H. French, L. K.
DeNoyer, W. -Y. Ching, Y. -N. Xu,
"Critical Point Analysis of the Interband Transition Strength of
Electrons", Journal of Physics D, 29 1740-50 (1996).
Interband transition strengths, Jcv, of AlN (red) and Al2O3 (blue) determined from VUV reflectivity. |
Interband transition strengths , Jcv, of three phases of Al2O3 determined from Valence-EELS with comparison to VUV results for alpha Al2O3.
R. H. French, "Electronic Structure of a-Al2O3 , with Comparison to AlON and AlN", Journal of the American Ceramic Society, 73, 3, 477-89, (1990).
As the uses of Al2O3 and other ceramics expand into new and more demanding applications it is increasingly important to understand their electronic structure and its relationship to properties. However compared with metals, semiconductors or alkali halides, our understanding of the electronic structure of ceramic materials is limited. There has been much recent progress in our understanding of the electronic structure of Al2O3, based on the applications of new experimental and theoretical methods. Vacuum ultraviolet spectroscopy and valence band photoemission spectroscopy coupled with Pseudofunction band structure methods provide a comprehensive approach to study a wide variety of electronic structure issues of importance to ceramic materials. The high temperature electronic structure and its role in determining the high temperature, intrinsic, electronic conductivity gives us the ability to evaluate high temperature conductivity data, and supports the conclusion that Al2O3 is predominantly an electronic conductor at high temperatures. The strain dependence of the electronic structure, as embodied in the deformation potentials, provides a simple method to determine surface stresses and strains. The variation of the electronic structure in the family Al2O3-AlON-AlN demonstrates the changes associated with the valence band chemistry of changing the anion from oxygen to nitrogen, and the bonding from mixed ionic-covalent in the direction of greater covalency. These changes in the anion valence bands lead to dramatic changes in the atomic and electronic nature of room temperature bimaterial interface formation for copper to Al2O3 or AlN. The application of this new methodology to develop our perspective on electronic structure and apply it to problems associated with temperature, stress, composition, or interface formation can improve our understanding of many critical questions in ceramics.
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Comment: (c) 2009 Roger H. French , frenchrh@lrsm.upenn.edu |
