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Real-time in situ optical tracking of oxygen vacancy migration in memristors

Nature Electronics volume 3, pages 687–693 (2020)Cite this article

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Abstract

Resistive switches, which are also known as memristors, are low-power, nanosecond-response devices that are used in a range of memory-centric technologies. Driven by an externally applied potential, the switching mechanism of valence change resistive memories involves the migration, accumulation and rearrangement of oxygen vacancies within a dielectric medium, leading to a change in electrical conductivity. The ability to look inside these devices and understand how morphological changes characterize their function has been vital in their development. However, current technologies are often destructive and invasive. Here, we report a non-destructive optical spectroscopy technique that can detect the motion of a few hundred oxygen vacancies with nanometre-scale sensitivity. Resistive switches are arranged in a nanoparticle-on-mirror geometry to exploit the high optical sensitivity to morphological changes occurring in tightly confined plasmonic hotspots within the switching material. Using this approach, we find that nanoscale oxygen bubbles form at the surface of a strontium titanate memristor film, leading ultimately to device breakdown on cycling.

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Fig. 1: Memristive device in a plasmonic geometry.
Fig. 2: Switching cycles of the NPoM memristive cell.
Fig. 3: Numerical simulation of optical gap modes.
Fig. 4: Numerical simulations of optical modes through the first switching cycle.

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Data availability

All source data for this work are available at https://doi.org/10.17863/CAM.55556.

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Acknowledgements

G.D.M. acknowledges support from the Winton Programme for the Physics of Sustainability. J.J.B. acknowledges funding from EPSRC grant no. EP/L027151/1 and NanoDTC EP/L015978/1, and W.L. and J.M.-D. from EPSRC grants nos. EP/L011700/1, EP/N004272/1 and EP/P007767/1 and the Isaac Newton Trust. A.D. acknowledges support from a Royal Society University Research Fellowship URF/R1/180097 and Royal Society Research Fellows Enhancement Award RGF/EA/181038. B.d.N. acknowledges support from the Leverhulme Trust and the Isaac Newton Trust in the form of an ECF. The US–UK collaborative effort was funded by the US National Science Foundation (ECCS-1902644 (Purdue University) and ECCS-1902623 (University at Buffalo, SUNY)) and EPRSC grant no. EP/T012218/1. J.M.-D. also acknowledges funding from the UK Royal Academy of Engineering, grant no. CiET1819_24. B.Z. acknowledges support from the China Scholarship Council and Cambridge Commonwealth, European and International Trust.

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Author notes

  1. These authors contributed equally: Giuliana Di Martino, Angela Demetriadou, Weiwei Li.

Authors and Affiliations

  1. NanoPhotonics Centre, Cavendish Laboratory, University of Cambridge, Cambridge, UK

    Giuliana Di Martino, Dean Kos, Bart de Nijs & Jeremy J. Baumberg

  2. Department of Materials Science and Metallurgy, University of Cambridge, Cambridge, UK

    Giuliana Di Martino, Weiwei Li, Bonan Zhu & Judith MacManus-Driscoll

  3. School of Physics and Astronomy, University of Birmingham, Birmingham, UK

    Angela Demetriadou

  4. School of Materials Engineering, Purdue University, West Lafayette, IN, USA

    Xuejing Wang & Haiyan Wang

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  1. Giuliana Di Martino
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Contributions

Experiments were devised by G.D.M. and J.J.B. and performed by G.D.M., with support for the chemical nanoassembly and sample preparation from D.K. The custom-made cantilever contacting set-up was realized by D.K. W.L. synthesized the STO/TiN films, performed X-ray diffraction and atomic force microscopy, with support from X.W. and H.W. for the TEM measurements. DFT calculations were performed by B.Z., guided by W.L., and FDTD simulations by A.D. The data analysis was performed by G.D.M., with support from all authors. The manuscript was written with contributions from all authors.

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Correspondence to Giuliana Di Martino or Jeremy J. Baumberg.

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Supplementary Figs. 1–16 and sections A–H.

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Di Martino, G., Demetriadou, A., Li, W. et al. Real-time in situ optical tracking of oxygen vacancy migration in memristors. Nat Electron 3, 687–693 (2020). https://doi.org/10.1038/s41928-020-00478-5

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