Models of defects in wide-gap oxides: Perspective and
challenges
A. L. Shlugera, A. S. Foster
,
, b, J. L. Gavartina, P. V. Sushkoa
aDepartment of Physics and Astronomy, University College
London, Gower Street, London WC1E 6BT, UK
bLaboratory of Physics, Helsinki University of Technology,
P.O. Box 1100, FIN-02015 HUT, Finland
In this chapter we will review some of the main issues and recent calculations pertaining mainly to point defects and defect processes in oxides. Several years of exploratory research and hundreds of publications have not lead so far to a final consensus about the materials to be used in DRAM and gate applications in future devices. The prevailing line of thought at the moment seems to favour "something ZrO2 or HfO2-based". Although the situation remains fluid, these materials as well as silicates and aluminates emerged as strong contenders and provide good examples of typical defect related issues. Therefore we will use them, were appropriate, to illustrate the present state of the art of calculations and main conclusions relevant to the performance of oxide materials. To some extent we will be following empirical approaches, which rely on knowledge of other materials in similar states to those to be used. Therefore we will draw some analogies with other oxides, such as silica and MgO. The properties we are going to consider will relate mainly to non-stoichiometry and disorder of prospective materials. We will discuss the mechanisms of defect diffusion and will review the relation between defects and transparent conductive behaviour of traditional and newly emerging materials, such as ITO and 12CaO . 7Al2O3.
Author Keywords: defects, oxides, electronic structure theory, electron trapping,
transparent conductors.
