Determination of miscibility in MgO-ZnO nanocrystal alloys by x-ray absorption spectroscopy

Abstract

The local structure of MgxZn1−xO nanocrystals is studied using synchrotron x-ray absorption near edge structures (XANES) over the full range of composition, from x = 0 to 1. Mg and Zn K-edges XANES measurements allow us to selectively study the local environments around Mg and Zn atoms in these nanocrystalline samples. Our results indicate that, for MgO-ZnO alloys, Zn is highly miscible in the rocksalt domain (i.e., up to ∼50 at. %) while the miscibility of Mg in the wurtzite domain is much less but is still substantial (i.e., up to ∼20 at. %). The simulated XANES spectra, based on first principles methods, are consistent with the observed spectra, confirming our finding. Because it is short-ranged and element-specific, the technique is useful for local structure and crystal phase determination of nanostructures, quantum dots, and mixed-phase alloys in general.