Understanding the defect structure of solution grown zinc oxide

Zinc oxide (ZnO) is a wide bandgap semiconducting oxide with many potential applications in various optoelectronic devices such as light emitting diodes (LEDs) and field effect transistors (FETs). Much effort has been made to understand the ZnO structure and its defects. However, one major issue in determining whether it is Zn or O deficiency that provides ZnO its unique properties remains. X-ray absorption spectroscopy (XAS) is an ideal, atom specific characterization technique that is able to probe defect structure in many materials, including ZnO. In this paper, comparative studies of bulk and aqueous solution grown (≤90 °C) ZnO powders using XAS and x-ray pair distribution function (XPDF) techniques are described. The XAS Zn–Zn correlation and XPDF results undoubtedly point out that the solution grown ZnO contains Zn deficiency, rather than the O deficiency that were commonly reported. This understanding of ZnO short range order and structure will be invaluable for further development of solid state lighting and other optoelectronic device applications.

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► ZnO powders have been synthesized through an aqueous solution method.
► Defect structure studied using XAS and XPDF.
► Zn–Zn correlations are less in the ZnO powders synthesized in solution than bulk.
► Zn vacancies are present in the powders synthesized.
► EXAFS and XPDF, when used complementary, are useful characterization techniques.