Electronic Band Structure of Al 2 O 3 , with Comparison to Alon and AIN

Abstract

As the uses of Al 2 O 3 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 Al 2 O 3 , based on the applications of new experimental and theoretial 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 Al 2 O 3 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 Al 2 O 3 ‐AION‐AIN demonstrates the changes associated with the valence band chemistry of changing the anion from oxygen to nitrogen, and the bonding from mixed ioniccovalent 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 Al 2 O 3 or AIN. 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.