Skip to main content

Thank you for visiting You are using a browser version with limited support for CSS. To obtain the best experience, we recommend you use a more up to date browser (or turn off compatibility mode in Internet Explorer). In the meantime, to ensure continued support, we are displaying the site without styles and JavaScript.

100 GHz zinc oxide Schottky diodes processed from solution on a wafer scale


Inexpensive radio-frequency devices that can meet the ultrahigh-frequency needs of fifth- and sixth-generation wireless telecommunication networks are required. However, combining high performance with cost-effective scalable manufacturing has proved challenging. Here, we report the fabrication of solution-processed zinc oxide Schottky diodes that can operate in microwave and millimetre-wave frequency bands. The fully coplanar diodes are prepared using wafer-scale adhesion lithography to pattern two asymmetric metal electrodes separated by a gap of around 15 nm, and are completed with the deposition of a zinc oxide or aluminium-doped ZnO layer from solution. The Schottky diodes exhibit a maximum intrinsic cutoff frequency in excess of 100 GHz, and when integrated with other passive components yield radio-frequency energy-harvesting circuits that are capable of delivering output voltages of 600 mV and 260 mV at 2.45 GHz and 10 GHz, respectively.

This is a preview of subscription content, access via your institution

Relevant articles

Open Access articles citing this article.

Access options

Rent or buy this article

Get just this article for as long as you need it


Prices may be subject to local taxes which are calculated during checkout

Fig. 1: Fabrication of nanogap electrodes and radio-frequency Schottky diode structure.
Fig. 2: D.c. characteristics and operational principle of ZnO and Al–ZnO nanogap Schottky diodes.
Fig. 3: High-frequency operation of ZnO-based nanogap Schottky diodes.
Fig. 4: Output voltage capabilities of the ZnO-based rectifier.

Data availability

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


  1. Kim, D. & Zarri, M. (eds) Road to 5G: Introduction and Migration (GSMA, 2018).

  2. Ilderem, V. The technology underpinning 5G. Nat. Electron. 3, 5–6 (2020).

    Article  Google Scholar 

  3. Dang, S., Amin, O., Shihada, B. & Alouini, M.-S. What should 6G be? Nat. Electron. 3, 20–29 (2020).

    Article  Google Scholar 

  4. Yang, P., Xiao, Y., Xiao, M. & Li, S. 6G wireless communications: vision and potential techniques. IEEE Netw. 33, 70–75 (2019).

    Article  MathSciNet  Google Scholar 

  5. Ni, Y., Liang, J., Shi, X. & Ban, D. Research on key technology in 5G mobile communication network. In 2019 International Conference on Intelligent Transportation, Big Data & Smart City (ICITBS) 199–201 (IEEE, 2019).

  6. Nagatsuma, T., Ducournau, G. & Renaud, C. C. Advances in terahertz communications accelerated by photonics. Nat. Photon. 10, 371–379 (2016).

    Article  Google Scholar 

  7. Schlecht, M. T., Preu, S., Malzer, S. & Weber, H. B. An efficient terahertz rectifier on the graphene/SiC materials platform. Sci. Rep. 9, 11205 (2019).

    Article  Google Scholar 

  8. Zhang, J. et al. Room temperature processed ultrahigh-frequency indium–gallium–zinc–oxide Schottky diode. IEEE Electron Device Lett. 37, 389–392 (2016).

    Article  Google Scholar 

  9. Semple, J. et al. Radio frequency coplanar ZnO Schottky nanodiodes processed from solution on plastic substrates. Small 12, 1993–2000 (2016).

    Article  Google Scholar 

  10. Park, H. et al. Fully roll-to-roll gravure printed rectenna on plastic foils for wireless power transmission at 13.56 MHz. Nanotechnology 23, 344006 (2012).

    Article  Google Scholar 

  11. Beesley, D. J. et al. Sub-15-nm patterning of asymmetric metal electrodes and devices by adhesion lithography. Nat. Commun. 5, 3933 (2014).

    Article  Google Scholar 

  12. Lin, Y.-H. et al. Al-doped ZnO transistors processed from solution at 120 °C. Adv. Electron. Mater. 2, 1600070 (2016).

    Article  Google Scholar 

  13. Semple, J., Wyatt-Moon, G., Georgiadou, D. G., McLachlan, M. A. & Anthopoulos, T. D. Semiconductor-free nonvolatile resistive switching memory devices based on metal nanogaps fabricated on flexible substrates via adhesion lithography. IEEE Trans. Electron Devices 64, 1973–1980 (2017).

    Article  Google Scholar 

  14. Georgiadou, D. G. et al. High responsivity and response speed single-layer mixed-cation lead mixed-halide perovskite photodetectors based on nanogap electrodes manufactured on large-area rigid and flexible substrates. Adv. Funct. Mater. 29, 1901371 (2019).

    Article  Google Scholar 

  15. Lin, Y.-H. et al. High-performance ZnO transistors processed via an aqueous carbon-free metal oxide precursor route at temperatures between 80–180 °C. Adv. Mater. 25, 4340–4346 (2013).

    Article  Google Scholar 

  16. Janotti, A. & Van de Walle, C. G. Fundamentals of zinc oxide as a semiconductor. Rep. Prog. Phys. 72, 126501 (2009).

    Article  Google Scholar 

  17. Zamiri, R., Singh, B., Scott Belsley, M. & Ferreira, J. M. F. Structural and dielectric properties of Al-doped ZnO nanostructures. Ceram. Int. 40, 6031–6036 (2014).

    Article  Google Scholar 

  18. Georgiadou, D. G., Semple, J. & Anthopoulos, T. D. Adhesion lithography for fabrication of printed radio-frequency diodes. SPIE Newsroom (2017).

  19. Meng, G., Cheng, Y., Wu, K. & Chen, L. Electrical characteristics of nanometer gaps in vacuum under direct voltage. IEEE Trans. Dielectr. Electr. Insul. 21, 1950–1956 (2014).

    Article  Google Scholar 

  20. Hemour, S. & Wu, K. Radio-frequency rectifier for electromagnetic energy harvesting: development path and future outlook. Proc. IEEE 102, 1667–1691 (2014).

    Article  Google Scholar 

  21. Zhang, X. et al. Two-dimensional MoS2-enabled flexible rectenna for Wi-Fi-band wireless energy harvesting. Nature 566, 368–372 (2019).

    Article  Google Scholar 

  22. Kim, H. K. & Mathur, M. Structural and electrical properties of ZnO films deposited on GaAs substrates by RF magnetron sputtering. MRS Proc. 238, 317 (1991).

    Article  Google Scholar 

  23. Alexander, T. P. et al. Dielectric properties of sol–gel derived ZnO thin films. in ISAF96. Proc. 10th IEEE International Symposium on Applications of Ferroelectrics Vol. 2, 585–588 (IEEE, 1996).

  24. Almora, O., Aranda, C., Mas-Marzá, E. & Garcia-Belmonte, G. On Mott–Schottky analysis interpretation of capacitance measurements in organometal perovskite solar cells. Appl. Phys. Lett. 109, 173903 (2016).

    Article  Google Scholar 

  25. Knapp, E. & Ruhstaller, B. The role of shallow traps in dynamic characterization of organic semiconductor devices. J. Appl. Phys. 112, 024519 (2012).

    Article  Google Scholar 

  26. Montero, J. M., Bisquert, J., Garcia-Belmonte, G., Barea, E. M. & Bolink, H. J. Trap-limited mobility in space-charge limited current in organic layers. Org. Electron. 10, 305–312 (2009).

    Article  Google Scholar 

  27. Dascǎlu, D. Trapping and transit-time effects in high-frequency operation of space-charge-limited dielectric diodes: frequency characteristics. Solid-State Electron. 11, 491–499 (1968).

    Article  Google Scholar 

  28. Zhang, J. et al. Flexible indium–gallium–zinc–oxide Schottky diode operating beyond 2.45 GHz. Nat. Commun. 6, 7561–7561 (2015).

    Article  Google Scholar 

  29. Wang, B. et al. High-k gate dielectrics for emerging flexible and stretchable electronics. Chem. Rev. 118, 5690–5754 (2018).

    Article  Google Scholar 

  30. Semple, J., Georgiadou, D. G., Wyatt-Moon, G., Gelinck, G. & Anthopoulos, T. D. Flexible diodes for radio frequency (RF) electronics: a materials perspective. Semicond. Sci. Technol. 32, 123002 (2017).

    Article  Google Scholar 

  31. Chasin, A. et al. An integrated a-IGZO UHF energy harvester for passive RFID tags. IEEE Trans. Electron Devices 61, 3289–3295 (2014).

    Article  Google Scholar 

  32. Lin, C.-Y. et al. High-frequency polymer diode rectifiers for flexible wireless power-transmission sheets. Org. Electron. 12, 1777–1782 (2011).

    Article  Google Scholar 

  33. Heljo, P., Lilja, K. E., Majumdar, H. S. & Lupo, D. High rectifier output voltages with printed organic charge pump circuit. Org. Electron. 15, 306–310 (2014).

    Article  Google Scholar 

  34. Li, M. et al. 0.7-GHz solution-processed indium oxide rectifying diodes. IEEE Trans. Electron Devices 67, 360–364 (2020).

    Article  Google Scholar 

  35. Sani, N. et al. All-printed diode operating at 1.6 GHz. Proc. Natl Acad. Sci. USA 111, 11943–11948 (2014).

    Article  Google Scholar 

  36. Sani, N. et al. Flexible lamination-fabricated ultrahigh frequency diodes based on self-supporting semiconducting composite film of silicon micro-particles and nano-fibrillated cellulose. Sci. Rep. 6, 28921 (2016).

  37. Manohara, H. M., Wong, E. W., Schlecht, E., Hunt, B. D. & Siegel, P. H. Carbon nanotube Schottky diodes using Ti−Schottky and Pt−Ohmic contacts for high frequency applications. Nano Lett. 5, 1469–1474 (2005).

    Article  Google Scholar 

  38. Cobas, E. & Fuhrer, M. S. Microwave rectification by a carbon nanotube Schottky diode. Appl. Phys. Lett. 93, 043120 (2008).

    Article  Google Scholar 

  39. Yang, X. & Chahal, P. Large-area low-cost substrate compatible CNT Schottky diode for THz detection. In 2011 IEEE 61st Electronic Components and Technology Conference (ECTC) 2158–2164 (IEEE, 2011).

  40. Kaur, A., Yang, X., Park, K. Y. & Chahal, P. Reduced graphene oxide based Schottky diode on flex substrate for microwave circuit applications. In 2013 IEEE 63rd Electronic Components and Technology Conference 1037–1042 (IEEE, 2013).

  41. Yang, S. J. et al. Ultrafast 27 GHz cutoff frequency in vertical WSe2 Schottky diodes with extremely low contact resistance. Nat. Commun. 11, 1574 (2020).

    Article  Google Scholar 

  42. Mishra, C., Pfeiffer, U., Rassel, R. & Reynolds, S. Silicon Schottky diode power converters beyond 100 GHz. In 2007 IEEE Radio Frequency Integrated Circuits (RFIC) Symposium 547–550 (IEEE, 2007).

  43. Sankaran, S. & O, K. K. Schottky diode with cutoff frequency of 400 GHz fabricated in 0.18 μm CMOS. Electron. Lett. 41, 506–508 (2005).

    Article  Google Scholar 

  44. Son, Y., Frost, B., Zhao, Y. & Peterson, R. L. Monolithic integration of high-voltage thin-film electronics on low-voltage integrated circuits using a solution process. Nat. Electron. 2, 540–548 (2019).

    Article  Google Scholar 

Download references


D.G.G., J.S. and T.D.A. acknowledge financial support from the European Union Horizon 2020 research and innovation programme under the Marie Skłodowska-Curie grant agreement 706707, the European Research Council (ERC) project AMPRO under grant no. 280221, the Engineering and Physical Sciences Research Council (EPSRC) grant no. EP/P505550/1 and the EPSRC Centre for Innovative Manufacturing in Large Area Electronics (CIM-LAE) grant no. EP/K03099X/1. A.S., K.L., H.F. and T.D.A. acknowledge support by the King Abdullah University of Science and Technology (KAUST) Office of Sponsored Research (OSR) under award no. OSR-2018-CARF/CCF-3079. A.A.S. thanks SERB for an Early Research Career Award (ECR/2017/1562) and SRM IST for financial support. We also thank S. Kano for helpful discussion on the nanogap size analysis.

Author information

Authors and Affiliations



T.D.A., D.G.G. and J.S. conceived the project. T.D.A. guided and supervised the project. D.G.G. and J.S. fabricated the small-scale devices and performed electrical measurements. D.G.G. analysed the data. A.A.S. set up the high-frequency rectifier circuit measurements and D.G.G., J.S. and A.A.S. analysed the data. D.G.G., H.F. and P.R. performed the single-port measurements and extracted and analysed the data. Y.-H.L. provided the Al-doped ZnO formulations. A.S., K.L. and H.F. carried out SEM and TEM characterization and performed statistical analysis on data derived from microscopy images. F.A. assisted with fabrication of wafer-scale devices and their electrical characterization. D.G.G. and T.D.A. wrote the first draft of the manuscript. All authors discussed the results and contributed to the final version of the paper.

Corresponding authors

Correspondence to Dimitra G. Georgiadou or Thomas D. Anthopoulos.

Ethics declarations

Competing interests

The authors declare no competing interests.

Additional information

Publisher’s note Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations.

Supplementary information

Supplementary Information

Supplementary Notes 1–7, Figs 1–14, Tables 1–3 and references.

Rights and permissions

Reprints and Permissions

About this article

Verify currency and authenticity via CrossMark

Cite this article

Georgiadou, D.G., Semple, J., Sagade, A.A. et al. 100 GHz zinc oxide Schottky diodes processed from solution on a wafer scale. Nat Electron 3, 718–725 (2020).

Download citation

  • Received:

  • Accepted:

  • Published:

  • Issue Date:

  • DOI:

This article is cited by


Quick links

Nature Briefing

Sign up for the Nature Briefing newsletter — what matters in science, free to your inbox daily.

Get the most important science stories of the day, free in your inbox. Sign up for Nature Briefing