Abstract
At present there is no ‘ideal’ thin-film transistor technology for demanding display applications, such as organic light-emitting diode displays, that allows combining the low-temperature, solution-processability offered by organic semiconductors with the high level of performance achievable with microcrystalline silicon1. N-type amorphous mixed metal oxide semiconductors, such as ternary oxides Mx1My2Oz, where M1 and M2 are metals such as In, Ga, Sn, or Zn, have recently gained momentum because of their high carrier mobility and stability2,3 and good optical transparency, but they are mostly deposited by sputtering. So far no route is available for forming high-performance mixed oxide materials from solution at low process temperatures <250 °C. Ionic mixed metal oxides should in principle be ideal candidates for solution-processable materials because the conduction band states derived from metal s-orbitals are relatively insensitive to the presence of structural disorder and high charge carrier mobilities are achievable in amorphous structures2. Here we report the formation of amorphous metal oxide semiconducting thin-films using a ‘sol–gel on chip’ hydrolysis approach from soluble metal alkoxide precursors, which affords unprecedented high field-effect mobilities of 10 cm2 V−1 s−1, reproducible and stable turn-on voltages Von≈0 V and high operational stability at maximum process temperatures as low as 230 °C.
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Acknowledgements
This work was supported by a grant from Panasonic Corporation. We would like to thank W. Jennings (Swagelok Center for Surface Analysis of Materials, OH USA) for XPS analysis, A. Chew and D. Sykes (Loughborough Surface Analysis, UK) for SIMS analysis, and D. Morgan (XPS Analysis Centre Cardiff University) for valuable discussions on XPS analysis. TEM cross-sectional analysis was conducted at Loughborough University, by J. Bates. We would also like to thank G. Nikiforov for help with SEM imaging.
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The metal oxide solution process development was carried out by K.K.B., K.M., Y.Y. and R.L.P. T.L. prepared the chemical precursors. Thin-film transistor and device performance was recorded by K.K.B. and Y.Y using protocols provided by R.L.P, K.M. and Y.Y. Constant current bias stress tests were developed by R.L.P., with contributions from Y.Y. J.R. recorded TEM and SEM images. The manuscript was prepared by K.K.B. and H.S. All authors examined and commented on the manuscript. The project was guided by H.S.
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Banger, K., Yamashita, Y., Mori, K. et al. Low-temperature, high-performance solution-processed metal oxide thin-film transistors formed by a ‘sol–gel on chip’ process. Nature Mater 10, 45–50 (2011). https://doi.org/10.1038/nmat2914
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DOI: https://doi.org/10.1038/nmat2914
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