The 6-coordinated cation site is the fundamental structural unit of the most effective transparent conducting oxides. Contrary to this established trend, anion deficient, fluorite related Ga2In6Sn2O16 (GITO) maintains 4-, 6-, 7-, and 8-coordinated cation sites and yet exhibits high conductivity. We investigate the interplay of the coordination site and electron transport in this material by partially replacing the Sn in GITO with Ti, Zr, or Hf. A combined approach of DFT-based calculations, X-ray diffraction, and neutron diffraction establishes that the substitution occurs preferentially on the 7-coordinate site. In contrast to the Sn that is being replaced, Ti, Zr, and Hf have empty d orbitals that promote spd covalency with the surrounding oxygen, which causes electron scattering and decreases the conductivity. Pairing the magnitude of this decrease with the experimentally and computationally determined site preference demonstrates that the 7-coordinate site is a major contributor to the conductivity. The 6-coordinate site also contributes to the conductivity, but to a lesser degree. Optical band gaps are shown to be site independent, however, and they increase as a function of increased carrier concentration and d0 metal content. Continued replacement of Sn after all 7-coordinate Sn has been substituted results in the formation of a 7-coordinate In antisite or replacement of 6-coordinate Sn, depending on the identity of the d0 substitute.

Electron transport in Ga2In6Sn2O16: The role of the 7-coordinate site

251st National Meeting (2016)

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