Abstract
Insulator–metal transitions are well known in transition-metal oxides, but inducing an insulator–metal transition in the oxide of a main group element is a major challenge. Here, we report the observation of an insulator–metal transition, with a conductivity jump of seven orders of magnitude, in highly non-stoichiometric, amorphous gallium oxide of approximate composition GaO1.2 at a temperature around 670 K. We demonstrate through experimental studies and density-functional-theory calculations that the conductivity jump takes place at a critical gallium concentration and is induced by crystallization of stoichiometric Ga2O3 within the metastable oxide matrix—in chemical terms by a disproportionation. This novel mechanism—an insulator–metal transition driven by a heterogeneous solid-state reaction—opens up a new route to achieve metallic behaviour in oxides that are expected to exist only as classic insulators.
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Acknowledgements
We gratefully acknowledge support by the Deutsche Forschungsgemeinschaft (DFG) within the Priority Program 1136. We thank J. Rodesch for carrying out preliminary measurements; R. Dronskowski for allowing us to use the Quantum Design PPMS; HASYLAB for the provision of beam time and travel funding; E. Welter, W. Calibe, J. Brendt, D. Müller and D. Röhrens for support during the X-ray absorption spectroscopy measurements; and T. Weirich for the TEM measurements.
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Nagarajan, L., De Souza, R., Samuelis, D. et al. A chemically driven insulator–metal transition in non-stoichiometric and amorphous gallium oxide. Nature Mater 7, 391–398 (2008). https://doi.org/10.1038/nmat2164
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DOI: https://doi.org/10.1038/nmat2164
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