Evidence for tetrahedral zinc in amorphous In_2-2xZn _xSn_xO₃ (a-ZITO)

The structure of amorphous In_2-2xZn_xSn _xO₃ (a-ZITO, x = 0.2, 0.3, 0.4) was investigated with transmission electron microscopy (TEM), the total scattering pair-distribution function (PDF) and X-ray absorption spectroscopy (XAS), which revealed a well-defined short-range structure that differed from the crystalline bixbyite and corundum ZITO polymorphs. The X-ray absorption near edge structure (XANES) and extended X-ray absorption fine structure (EXAFS) were used to detect InO₆ and SnO₆ octahedra and ZnO₄ tetrahedra in a-ZITO, which differ from the InO₆, SnO₆ and ZnO ₆ pseudo-octahedra that are observed in the bixbyite and corundum ZITO polymorphs. The formation of the ZnO₄ tetrahedron likely inhibits the crystallization of ZITO when synthesized under mild conditions. in situ XRD showed a gradual transition from a-ZITO to a mixture of the bixbyite and corundum ZITO polymorphs as the temperature was raised from 300 °C to 568 °C.