We report on the electronic properties of both amorphous and polycrystalline zinc-indium oxide thin films with similar degenerate electron concentrations just above the insulator-to-metal transition. The highest electron mobilities occur in amorphous oxide films deposited at 100 °C; for these, structural disorder is on a spatial scale much smaller than the characteristic electron wavelength (∼3 nm) of the conduction electron gas. For polycrystalline films fabricated at 200–300 °C enhanced electron scattering occurs at evolving grain boundaries when the grain size is comparable to the electron wavelength. Larger, highly crystalline grains form for deposition at 500 °C with concomitant higher carrier mobilities.

The electronic structure of In 4 Sn 3 O 12 has been studied by optical and x-ray photoemission spectroscopies and has been compared to electronic structure calculations carried out using density-functional theory. An excellent agreement is found between the experimental valence-band structure and that predicted by the calculations. The valence band derives its dominant character from O 2p states with three distinct features emerging from the hybridization with In and Sn 5s, 5p, and 4d states, respectively. The position of the valence-band edge in the x-ray photoemission spectrum suggests a fundamental electronic gap of 2.7 eV whereas the onset of strong optical absorption is predicted to occur at 3.3 eV.

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The electronic structures of In4Sn3O12, In5SnSbO12 and the intermediate solid solution In4+xSn3−2xSbxO12 have been studied by x-ray photoemission spectroscopy. The surfaces were found be consistently rich in indium and deficient in tin, with the extent of the deviation from bulk stoichiometry decreasing with increasing cosubstitution of In and Sb for Sn. We find that the valence band structure of the In4+xSn3−2xSbxO12 solid solution evolves with the degree of cosubstitution and shows well-defined features that arise from the hybridization of O 2p states with In 5s, Sn 5s, and Sb 5s states. We determine the fundamental electronic gaps of In4Sn3O12 and In5SnSbO12 as 2.66 eV and 2.79 eV, respectively.

Highly conductive (> 10 3 Ω -1 cm -1 ) and transparent (~ 90%) In 4 Sn 3 O 12 films have been deposited using pulsed laser deposition (PLD) on glass substrates held at a temperature of 500ºC under varying pressures of oxygen (2.5 mTorr ≤ P O2 ≤ 15 mTorr). The crystallinity and the roughness of the films were found to increase with the pressure of oxygen used during deposition. Electron concentrations of the order of 5x10 20 cm -3 and mobilities as high as 30 cm 2 V -1 s -1 were derived from the measurement of Hall coefficients. Both the electronic transport and optical properties of the films were found to be strongly sensitive to the pressure of oxygen used during deposition.