Flexible metal-oxide devices made by room-temperature photochemical activation of sol–gel films

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Abstract

Amorphous metal-oxide semiconductors have emerged as potential replacements for organic and silicon materials in thin-film electronics. The high carrier mobility in the amorphous state, and excellent large-area uniformity, have extended their applications to active-matrix electronics, including displays, sensor arrays and X-ray detectors1,2,3,4,5,6,7. Moreover, their solution processability and optical transparency have opened new horizons for low-cost printable and transparent electronics on plastic substrates8,9,10,11,12,13. But metal-oxide formation by the sol–gel route requires an annealing step at relatively high temperature2,14,15,16,17,18,19, which has prevented the incorporation of these materials with the polymer substrates used in high-performance flexible electronics. Here we report a general method for forming high-performance and operationally stable metal-oxide semiconductors at room temperature, by deep-ultraviolet photochemical activation of sol–gel films. Deep-ultraviolet irradiation induces efficient condensation and densification of oxide semiconducting films by photochemical activation at low temperature. This photochemical activation is applicable to numerous metal-oxide semiconductors, and the performance (in terms of transistor mobility and operational stability) of thin-film transistors fabricated by this route compares favourably with that of thin-film transistors based on thermally annealed materials. The field-effect mobilities of the photo-activated metal-oxide semiconductors are as high as 14 and 7 cm2 V−1 s−1 (with an Al2O3 gate insulator) on glass and polymer substrates, respectively; and seven-stage ring oscillators fabricated on polymer substrates operate with an oscillation frequency of more than 340 kHz, corresponding to a propagation delay of less than 210 nanoseconds per stage.

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Figure 1: Photo-activation of solution-processed metal-oxide semiconductors by DUV.
Figure 2: Transfer characteristics of photo-annealed IGZO, IZO and In 2 O 3 TFTs using Al 2 O 3 and SiO 2 gate dielectric, and comparison with thermally annealed devices.
Figure 3: Electrical characteristics and bias stability of photo-annealed IGZO TFTs on flexible substrates.
Figure 4: Characteristics of seven-stage ring oscillators fabricated on a PAR substrate by photo-annealing.

References

  1. 1

    Nomura, K. et al. Room-temperature fabrication of transparent flexible thin-film transistors using amorphous oxide semiconductors. Nature 432, 488–492 (2004)

  2. 2

    Kim, M. G., Kanatzidis, M. G., Facchetti, A. & Marks, T. J. Low-temperature fabrication of high-performance metal oxide thin-film electronics via combustion processing. Nature Mater. 10, 382–388 (2011)

  3. 3

    Facchetti, A. & Marks, T. J. Transparent Electronics (Wiley, 2010)

  4. 4

    Dusastre, V. Materials for Sustainable Energy. (World Scientific, 2010)

  5. 5

    Kamiya, T., Nomura, K. & Hosono, H. Present status of amorphous In-Ga-Zn-O thin-film transistors. Sci. Technol. Adv. Mater. 11, 044305 (2010)

  6. 6

    Jeon, S. et al. Nanometer-scale oxide thin film transistor with potential for high-density image sensor applications. ACS Appl. Mater. Interfaces 3, 1–6 (2011)

  7. 7

    Kim, K. M. et al. Competitive device performance of low-temperature and all-solution-processed metal-oxide thin-film transistors. Appl. Phys. Lett. 99, 242109 (2011)

  8. 8

    Yang, S. et al. Low-temperature processed flexible In-Ga-Zn-O thin-film transistors exhibiting high electrical performance. Electron. Dev. Lett. 32, 1692–1694 (2011)

  9. 9

    Wager, J. F. Transparent electronics. Science 300, 1245–1246 (2003)

  10. 10

    Cao, Q. et al. Medium-scale carbon nanotube thin-film integrated circuits on flexible plastic substrates. Nature 454, 495–500 (2008)

  11. 11

    Klauk, H. Organic Electronics: Materials, Manufacturing and Applications (Wiley-VCH, 2006)

  12. 12

    Briseno, A. L. et al. Patterning organic single-crystal transistor arrays. Nature 444, 913–917 (2006)

  13. 13

    Sekitani, T., Zschieschang, U., Klauk, H. & Someya, T. Flexible organic transistors and circuits with extreme bending stability. Nature Mater. 9, 1015–1022 (2010)

  14. 14

    Han, S. Y., Herman, G. S. & Chang, C. Low-temperature, high-performance, solution-processed indium oxide thin-film transistors. J. Am. Chem. Soc. 133, 5166–5169 (2011)

  15. 15

    Jeong, S., Ha, Y. G., Moon, J., Facchetti, A. & Marks, T. J. Role of gallium doping in dramatically lowering amorphous-oxide processing temperatures for solution-derived indium zinc oxide thin-film transistors. Adv. Mater. 22, 1346–1350 (2010)

  16. 16

    Meyers, S. T. et al. Aqueous inorganic inks for low-temperature fabrication of ZnO TFTs. J. Am. Chem. Soc. 130, 17603–17609 (2008)

  17. 17

    Kim, Y. H., Han, J. I. & Park, S. K. Effect of Zn/Tin composition ratio on the operational stability of solution-processed zinc tin oxide thin film transistors. IEEE Electron Device Lett. 33, 50–52 (2012)

  18. 18

    Kim, Y. H., Han, M. K., Han, J. I. & Park, S. K. Effect of metallic composition on electrical properties of solution-processed indium-gallium-zinc-oxide thin film transistors. IEEE Trans. Electron. Dev. 57, 1009–1014 (2010)

  19. 19

    Adamopoulos, G. et al. High-mobility low-voltage ZnO and Li-doped ZnO transistors based on ZrO2 high-k dielectric grown by spray pyrolysis in ambient air. Adv. Mater. 23, 1894–1898 (2011)

  20. 20

    Van de Leest, R. E. UV photo-annealing of thin sol-gel films. Appl. Surf. Sci. 86, 278–285 (1995)

  21. 21

    Imai, H. in Handbook of Sol-Gel Science and Technology: Processing, Characterization and Applications Vol. 1 (ed. Sakka, S. ) 639–650 (Kluwer, 2005)

  22. 22

    Clark, T., Jr et al. A new application of UV-ozone treatment in the preparation of substrate-supported, mesoporous thin films. Chem. Mater. 12, 3879–3884 (2000)

  23. 23

    Imai, H., Tominaga, A., Hirashima, H., Toki, M. & Asakuma, N. Ultraviolet-reduced reduction and crystallization of indium oxide films. J. Appl. Phys. 85, 203–207 (1999)

  24. 24

    Park, Y. M., Daniel, J., Heeney, M. & Salleo, A. Room-temperature fabrication of ultrathin oxide gate dielectrics for low-voltage operation of organic field-effect transistors. Adv. Mater. 23, 971–974 (2011)

  25. 25

    Hwang, S., Lee, J. H., Woo, C. H., Lee, J. Y. & Cho, H. K. Effect of annealing temperature on the electrical performances of solution-processed InGaZnO thin film transistors. Thin Solid Films 519, 5146–5149 (2011)

  26. 26

    Lim, W. et al. Improvement in bias stability of amorphous-InGaZnO4 thin film transistors with SiOx passivation layers. J. Vac. Sci. Technol. B 28, 116–119 (2010)

  27. 27

    Son, K.-S. et al. Highly stable double-gate Ga-In-Zn-O thin-film transistor. Electron Dev. Lett. 31, 812–814 (2010)

  28. 28

    Cho, E. N., Kang, J. H., Kim, C. E., Moon, P. & Yun, I. Analysis of bias stress instability in amorphous InGaZnO thin-film transistors. IEEE Trans. Device Mater. Reliab. 11, 112–117 (2011)

  29. 29

    Choi, H. S. et al. Influence of Hf contents on interface state properties in a-HfInZnO thin-film transistors with SiNx/SiOx gate dielectrics. Appl. Phys. Lett. 99, 183502 (2011)

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Acknowledgements

We acknowledge discussions with C.-I. Kim, S.-H. Song, H.-I. Kwon, B.-S. Bae, Y. Hong, S. Lim, J.-I. Han, M. J. Lee, A. Fenoglio and K.-H. Kim. This work was partially supported by Basic Science Research Program (no. 2010-0002623) and World-Class University Program (no. R31-10026) through a National Research Foundation of Korea (NRF) grant funded by the Ministry of Education, Science, and Technology.

Author information

S.K.P. designed the project and experiments; Y.-H.K., J.-S.H., T.-H.K., S.P., J.K., M.S.O., M.-H.Y. and S.K.P. carried out the experiments; S.K.P. and Y.-H.K. discussed and interpreted all the results; M.-H.Y., G.-R.Y. and Y.-Y.N. gave conceptual advice on the chemistry-related experiments and discussions. S.K.P., Y.-H.K., M.-H.Y. and G.-R.Y. wrote the manuscript, with S.K.P. the lead writer. All authors read and commented on the manuscript.

Correspondence to Sung Kyu Park.

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The authors declare no competing financial interests.

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