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Flexible two-dimensional indium tin oxide fabricated using a liquid metal printing technique

Abstract

Indium tin oxide (ITO) is a transparent conductor used in applications such as touch screens, smart windows and displays. A key limitation of ITO is its brittle nature, which prohibits its use in flexible electronics. The commercial deposition of high-quality ITO also currently relies on a costly vacuum manufacturing approach. Here we report the centimetre-scale synthesis of flexible two-dimensional ITO using a low-temperature liquid metal printing technique. The approach can directly deposit monolayer or bilayer ITO onto desired substrates, with the resulting bilayer samples offering a transparency above 99.3% and a sheet resistance as low as 5.4 kΩ □−1. We also show that the bilayer ITO features a stratified structure with a pronounced van der Waals spacing. To illustrate the capabilities of the technique, we develop a capacitive touch screen using centimetre-sized monolayer ITO sheets.

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Fig. 1: Schematic of the 2D ITO printing process and LED demonstration circuit highlighting transparency and conductivity.
Fig. 2: Material characterizations of printed 2D ITO nanosheets.
Fig. 3: Morphological and crystalline characterizations of the 2D ITO sheets.
Fig. 4: Characterization of the flexibility of 2D ITO printed on polyimide substrates.
Fig. 5: Application of 2D ITO in a capacitive touch screen.

Data availability

The data that support the plots within this paper and other findings of this study are available from the corresponding author upon reasonable request.

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Acknowledgements

We acknowledge technical support and instrumentation access provided by the RMIT Microscopy and Microanalysis Facility (RMMF) and MicroNano Research Facility (MNRF) at RMIT University. T.D. acknowledges funding received through the ARC DECRA scheme (DE190100100). We also acknowledge financial support received from the ARC Centre of Excellence FLEET (CE170100039). D.E. acknowledges the Scientia Fellowship scheme at the University of New South Wales. N.S. and A.Z. acknowledge funding from the Australian Government Research Training Program Scholarship scheme. S.P.R. is supported by the ARC (CE170100026). This work was also supported by computational resources provided by the Australian Government through the National Computational Infrastructure National Facility and the Pawsey Supercomputer Centre. This work was performed in part at the Melbourne Centre for Nanofabrication (MCN) in the Victorian Node of the Australian National Fabrication Facility (ANFF).

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Contributions

The project was conceived, designed and directed by T.D., K.K.-Z. and D.E. R.S.D. and N.S. designed the synthesis methodology, experiments and device fabrications. R.S.D. synthesized monolayer 2D ITO and conducted AFM, flexible device fabrication and electrical measurements. N.S. synthesized bilayer 2D ITO, conducted a detailed AFM study of bilayer 2D ITO and fabricated devices for Hall effect measurements. A.Z. conducted TEM/SAED and HRTEM imaging and contributed to creating schematic illustrations. A.J. assisted with electronic device design and manufacture. M.M. contributed to device design and schematic illustrations. M.R. contributed to capacitive touch screen measurements. B.Y.Z. performed XPS measurements. M.A.R. contributed to four-point-probe measurements. P.A. assisted in the analysis of data and method development. K.A.M. contributed to device fabrication. M.B.G. performed cross-sectional TEM imaging. E.D.G. performed and analysed optical measurements. S.B. conducted Hall effect measurements and RIE etching. M.S.F. analysed and interpreted Hall effect data together with S.B. S.P.R. performed DFT calculations. C.F.M. contributed to the analysis of XPS data and contributed to the development of the theoretical framework. T.D., K.K.-Z., D.E., R.S.D. and N.S. analysed the results and prepared the manuscript. All authors revised the manuscript.

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Correspondence to Dorna Esrafilzadeh or Kourosh Kalantar-Zadeh or Torben Daeneke.

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Supplementary Figs. 1–13, Notes 1–3 and Table 1.

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Datta, R.S., Syed, N., Zavabeti, A. et al. Flexible two-dimensional indium tin oxide fabricated using a liquid metal printing technique. Nat Electron 3, 51–58 (2020). https://doi.org/10.1038/s41928-019-0353-8

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