Evolution of local structures in polycrystalline Zn1-xMgxO (0≤x≤0.15) studied by Raman spectroscopy and synchrotron x-ray pair-distribution-function analysis

The local structures of Zn1-xMgxO alloys have been studied by Raman spectroscopy and by synchrotron x-ray pair-distribution-function (PDF) analysis. Within the solid solution range (0 <= x <= 0.15) of Zn1-xMgxO, the wurtzite framework is maintained with Mg homogeneously distributed throughout the wurtzite lattice. The E-2(high) Raman line of Zn1-xMgxO displays systematic changes in response to the evolution of the crystal lattice upon the Mg substitution. The redshift and broadening of the E-2(high) mode are explained by the expansion of hexagonal ab dimensions and compositional disorder of Zn/Mg, respectively. Synchrotron x-ray PDF analyses of Zn1-xMgxO reveal that the Mg atoms have a slightly reduced wurtzite parameter u and more regular tetrahedral bond distances than the Zn atoms. For both Zn and Mg, the internal tetrahedral geometries are independent of the alloy composition.