Detection of spinel $\mathrm{ZnI}{\mathrm{n}}_2{\mathrm{O}}_4$ formed as nanostructures in ZnO

A local structure formed by dilute In ions doped in ZnO was investigated by means of a nuclear spectroscopic technique and density functional theory (DFT) calculations. Comparative studies on a presumably isomorphous $\mathrm{CdI}{\mathrm{n}}_2{\mathrm{O}}_4$ unveiled the local structure: the impurity In ions form in ZnO a spinel $\mathrm{ZnI}{\mathrm{n}}_2{\mathrm{O}}_4$, which has been only a hypothetical binary oxide so far. The most stable structure of the spinel was determined by DFT calculations, and the hyperfine interaction parameters obtained for the structure show excellent agreement with the experimental values. The experimental synthesis and detection of the normal spinel $\mathrm{ZnI}{\mathrm{n}}_2{\mathrm{O}}_4$ are presented.

Figure 1

TDPAC spectrum of ${}^{111}\mathrm{Cd}\left({\leftarrow }^{111}\mathrm{In}\right)$ in $\mathrm{CdI}{\mathrm{n}}_2{\mathrm{O}}_4$ measured at room temperature. A least-squares fit was performed with Eq. (2) for the perturbation factor.

Figure 2

TDPAC spectra of ${}^{111}\mathrm{Cd}\left({\leftarrow }^{111}\mathrm{In}\right)$ in 0.25-mol % $\mathrm{CdI}{\mathrm{n}}_2{\mathrm{O}}_4$-added ZnO measured (a) at 1000 K and (b) at room temperature and in 0.5-at. % In-doped ZnO measured (c) at 1000 K and (d) at room temperature. For the least-squares fits to the data, the damping factor $G_{22}^{*}\left(t\right)$ was incorporated in Eq. (2) for the perturbation factors [27, 28].

Figure 3

Schematic structure of the most stable $\mathrm{CdZ}{\mathrm{n}}_6\mathrm{I}{\mathrm{n}}_6{\mathrm{O}}_{14}$ cluster with $a=0.8775\mathrm{nm}$ and $u=0.250$. The violet, red, and gray spheres represent In, O, and Zn ions, respectively; and the octahedrally coordinated ion at the center is Cd substituting for In. For clarity of the structure, the oxygen ions are depicted in a relatively small size.