Nonstoichiometry defects

Furthermore, interactions between native (nonstoichiometry) defects like vacancies and impurities/dopants are observed in GaAs, resulting in electrically active complexes that influence compensation in SC GaAs and, therefore, have to be taken into account. Post-growth heat treatment of the crystals can by appHed to influence the defect equilibria. 

N. N. Greenwood, Ionic Crystals. Lattice Defects and Nonstoichiometry, Butterworths, London, 1968, 194 pp. 

Nonstoichiometry of the oxides can be due to a number of reasons, such as hydration,159 incomplete oxidation,158 and the generation of defects at interfaces.157 An important factor affecting the chemical composition of the oxides is the incorporation of electrolyte species into the growing alumina. There have even been suggestions to use this for impurity doping of oxides and modifying their properties.161 Various kinds of anion distributions and mechanisms of anion incorporation and their influence on oxide properties have been reported. The problems attracting attention are ... 

Equation 4.75 finds its application in the region of intrinsic disorder (a similar equation can be developed for Frenkel defects), where Schottky and Frenkel defects are dominant with respect to point impurities and nonstoichiometry. 

Nakamura A. and Schmalzried H. (1983). On the nonstoichiometry and point defects in olivine. Phys. Chem. Minerals, 10 27-37. 

In Chap. C, the thermodynamic and structural outlook of the bond, which had been the matter of discussion in Part A of this chapter, is further developed, and the model formalism, which takes advantage of the well known Friedel s model for d-transition metals but is inspired by the results of refined band calculations, is presented for metals and compounds. Also, a hint is given of the problems which are related to the nonstoichiometry of actinide oxides, such as clustering of defects. Actinide oxides present an almost purely ionic picture nevertheless, covalency is present in considerable extent, and is important for the defect structure. 

It is usually assumed that the dominant defect species responsible for nonstoichiometry is constituted by oxygen vacancies (rather than metal interstitials). This assumption can be justified on the basis of X-ray and neutron diffraction and density measurements . ... 

However, structural chemistry in oxides with large departures from stoichiometry cannot be solely explained by point defects. Defects cannot remain isolated and interactions between them begin to occur. Our discussion therefore begins with a general description of the fundamental knowledge about nonstoichiometry in oxides. Understanding such disorder and the complex defect... 

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