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.

Charge disproportionate molecular redox for discrete memristive and memcapacitive switching

An Author Correction to this article was published on 27 June 2023

This article has been updated


Electronic symmetry breaking by charge disproportionation results in multifaceted changes in the electronic, magnetic and optical properties of a material, triggering ferroelectricity, metal/insulator transition and colossal magnetoresistance. Yet, charge disproportionation lacks technological relevance because it occurs only under specific physical conditions of high or low temperature or high pressure. Here we demonstrate a voltage-triggered charge disproportionation in thin molecular films of a metal–organic complex occurring in ambient conditions. This provides a technologically relevant molecular route for simultaneous realization of a ternary memristor and a binary memcapacitor, scalable down to a device area of 60 nm2. Supported by mathematical modelling, our results establish that multiple memristive states can be functionally non-volatile, yet discrete—a combination perceived as theoretically prohibited. Our device could be used as a binary or ternary memristor, a binary memcapacitor or both concomitantly, and unlike the existing ‘continuous state’ memristors, its discrete states are optimal for high-density, ultra-low-energy digital computing.

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

Prices vary by article type



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

Fig. 1: Molecular and thin film electronic properties.
Fig. 2: Test structures and electrical characterizations.
Fig. 3: Compact memristor model and state trajectory.
Fig. 4: Identification of molecular states.
Fig. 5: Reaction coordinate diagram and the role of temperature in stabilizing the charge disproportionate state.
Fig. 6: Role of counterions in charge disproportionation.

Data availability

The data that support the findings of this study are available from the corresponding authors on reasonable request.

Change history


  1. Long, Y. et al. Temperature-induced A–B intersite charge transfer in an A-site-ordered LaCu3Fe4O12 perovskite. Nature 458, 60–63 (2009).

    Article  CAS  Google Scholar 

  2. Cheng, J. et al. Charge disproportionation and the pressure-induced insulator–metal transition in cubic perovskite PbCrO3. Proc. Natl Acad. Sci. USA 112, 1670–1674 (2015).

    Article  CAS  Google Scholar 

  3. Harter, J., Zhao, Z., Yan, J.-Q., Mandrus, D. & Hsieh, D. A parity-breaking electronic nematic phase transition in the spin-orbit coupled metal Cd2Re2O7. Science 356, 295–299 (2017).

    Article  CAS  Google Scholar 

  4. Kawamoto, T. et al. Interlayer charge disproportionation in the layered organic superconductor κH-(DMEDO-TSeF)2[Au(CN)4](THF) with polar dielectric insulating layers. Phys. Rev. Lett. 109, 147005 (2012).

    Article  Google Scholar 

  5. Senn, M. S., Wright, J. P. & Attfield, J. P. Charge order and three-site distortions in the Verwey structure of magnetite. Nature 481, 173 (2012).

    Article  CAS  Google Scholar 

  6. Moskvin, A. Perspectives of disproportionation driven superconductivity in strongly correlated 3d compounds. J. Phys. Condens. Matter 25, 085601 (2013).

    Article  CAS  Google Scholar 

  7. Shimakawa, Y., Kubo, Y. & Manako, T. Giant magnetoresistance in Ti2Mn2O7 with the pyrochlore structure. Nature 379, 53–55 (1996).

    Article  CAS  Google Scholar 

  8. Kusmartseva, A. F., Sipos, B., Berger, H., Forro, L. & Tutiš, E. Pressure induced superconductivity in Pristine 1T–TiSe2. Phys. Rev. Lett. 103, 236401 (2009).

    Article  CAS  Google Scholar 

  9. Zhang, J. et al. Cooperative photoinduced metastable phase control in strained manganite films. Nat. Mater. 15, 956–960 (2016).

    Article  CAS  Google Scholar 

  10. Yang, J. J. et al. High switching endurance in TaOx memristive devices. Appl. Phys. Lett. 97, 232102 (2010).

    Article  Google Scholar 

  11. Lee, M.-J. et al. A fast, high-endurance and scalable non-volatile memory device made from asymmetric Ta2O5–x/TaO2–x bilayer structures. Nat. Mater. 10, 625–630 (2011).

    Article  CAS  Google Scholar 

  12. Kumar, S. et al. Conduction channel formation and dissolution due to oxygen thermophoresis/diffusion in hafnium oxide memristors. ACS Nano 10, 11205–11210 (2016).

    Article  CAS  Google Scholar 

  13. Chua, L. Five non-volatile memristor enigmas solved. Appl. Phys. A 124, 563 (2018).

    Article  Google Scholar 

  14. Prezioso, M. et al. Training and operation of an integrated neuromorphic network based on metal-oxide memristors. Nature 521, 61–64 (2015).

    Article  CAS  Google Scholar 

  15. Sheridan, P. M. et al. Sparse coding with memristor networks. Nat. Nanotechnol. 12, 784–789 (2017).

    Article  CAS  Google Scholar 

  16. Nili, H. et al. Hardware-intrinsic security primitives enabled by analogue state and nonlinear conductance variations in integrated memristors. Nat. Electron. 1, 197–202 (2018).

    Article  Google Scholar 

  17. Yang, J. J., Strukov, D. B. & Stewart, D. R. Memristive devices for computing. Nat. Nanotechnol. 8, 13–24 (2013).

    Article  CAS  Google Scholar 

  18. Rütten, M., Kaes, M., Albert, A., Wuttig, M. & Salinga, M. Relation between bandgap and resistance drift in amorphous phase change materials. Sci. Rep. 5, 17362 (2015).

    Article  Google Scholar 

  19. Liu, R., Lee, H.-Y. & Yu, S. Analyzing inference robustness of RRAM synaptic array in low-precision neural network. In Proc. 47th European Solid-State Device Research Conference (ESSDERC) 18–21 (IEEE, 2017).

  20. Nagashima, K. et al. Resistive switching multistate nonvolatile memory effects in a single cobalt oxide nanowire. Nano Lett. 10, 1359–1363 (2010).

    Article  CAS  Google Scholar 

  21. Kim, W. et al. Multistate memristive tantalum oxide devices for ternary arithmetic. Sci. Rep. 6, 36652 (2016).

    Article  CAS  Google Scholar 

  22. Choi, S. et al. SiGe epitaxial memory for neuromorphic computing with reproducible high performance based on engineered dislocations. Nat. Mater. 17, 335–340 (2018).

    Article  CAS  Google Scholar 

  23. Wang, Z. et al. Memristors with diffusive dynamics as synaptic emulators for neuromorphic computing. Nat. Mater. 16, 101–108 (2017).

    Article  CAS  Google Scholar 

  24. Zidan, M. A. et al. A general memristor-based partial differential equation solver. Nat. Electron. 1, 411–420 (2018).

    Article  Google Scholar 

  25. Le Gallo, M. et al. Mixed-precision in-memory computing. Nat. Electron. 1, 246–253 (2018).

    Article  Google Scholar 

  26. Reed, D., Larus, J. R. & Gannon, D. Imagining the future: thoughts on computing. Computer 45, 25–30 (2012).

    Article  Google Scholar 

  27. Pan, J. & McElhannon, J. Future edge cloud and edge computing for internet of things applications. IEEE Internet Things J. 5, 439–449 (2018).

    Article  Google Scholar 

  28. Khan, H. N., Hounshell, D. A. & Fuchs, E. R. Science and research policy at the end of Moore’s law. Nat. Electron. 1, 14–21 (2018).

    Article  Google Scholar 

  29. Bhunia, P. et al. A non-volatile memory device consisting of graphene oxide covalently functionalized with ionic liquid. Chem. Commun. 48, 913–915 (2012).

    Article  CAS  Google Scholar 

  30. Cui, B.-B. et al. Tuning of resistive memory switching in electropolymerized metallopolymeric films. Chem. Sci. 6, 1308–1315 (2015).

    Article  CAS  Google Scholar 

  31. Bessonov, A. A. et al. Layered memristive and memcapacitive switches for printable electronics. Nat. Mater. 14, 199–204 (2015).

    Article  CAS  Google Scholar 

  32. Chan, H., Wong, H.-L., Ng, M., Poon, C.-T. & Yam, V. W.-W. Switching of resistive memory behavior from binary to ternary logic via alteration of substituent positioning on the subphthalocyanine core. J. Am. Chem. Soc. 139, 7256–7263 (2017).

    Article  CAS  Google Scholar 

  33. Hong, E. Y.-H., Poon, C.-T. & Yam, V. W.-W. A phosphole oxide-containing organogold(III) complex for solution-processable resistive memory devices with ternary memory performances. J. Am. Chem. Soc. 138, 6368–6371 (2016).

    Article  CAS  Google Scholar 

  34. Fan, F. et al. Conjugated polymer covalently modified graphene oxide quantum dots for ternary electronic memory devices. Nanoscale 9, 10610–10618 (2017).

    Article  CAS  Google Scholar 

  35. Wang, Z. et al. Capacitive neural network with neuro-transistors. Nat. Commun. 9, 3208 (2018).

    Article  Google Scholar 

  36. Chua, L. If it’s pinched it’s a memristor. Semicond. Sci. Technol. 29, 104001 (2014).

    Article  Google Scholar 

  37. Najem, J. S. et al. Dynamical nonlinear memory capacitance in biomimetic membranes. Nat. Commun. 10, 1–11 (2019).

    Google Scholar 

  38. Saeki, A. & Seki, S. in Chemical Science of π-Electron Systems (eds Akasaka, T. et al.) 605–620 (Springer, 2015).

  39. Goswami, S. et al. Robust resistive memory devices using solution-processable metal-coordinated azo aromatics. Nat. Mater. 16, 1216–1224 (2017).

    Article  CAS  Google Scholar 

  40. Paul, N. D., Rana, U., Goswami, S., Mondal, T. K. & Goswami, S. Azo anion radical complex of rhodium as a molecular memory switching device: isolation, characterization, and evaluation of current–voltage characteristics. J. Am. Chem. Soc. 134, 6520–6523 (2012).

    Article  CAS  Google Scholar 

  41. Goswami, S., Sengupta, D., Paul, N. D., Mondal, T. K. & Goswami, S. Redox non‐innocence of coordinated 2‐(arylazo)pyridines in iridium complexes: characterization of redox series and an insight into voltage‐induced current characteristics. Chem. Eur. J. 20, 6103–6111 (2014).

    Article  CAS  Google Scholar 

  42. Valov, I. & Kozicki, M. Non-volatile memories: organic memristors come of age. Nat. Mater. 16, 1170–1172 (2017).

    Article  CAS  Google Scholar 

  43. Tayi, A. S., Kaeser, A., Matsumoto, M., Aida, T. & Stupp, S. I. Supramolecular ferroelectrics. Nat. Chem. 7, 281–294 (2015).

    Article  CAS  Google Scholar 

  44. Jayaram, B. et al. Sanjeevini: a freely accessible web-server for target directed lead molecule discovery. BMC Bioinformatics 13, S7 (2012).

    Article  Google Scholar 

  45. Goswami, S., Mukherjee, R. & Chakravorty, A.Chemistry of ruthenium. 12. Reactions of bidentate ligands with diaquabis[2-(arylazo)pyridine]ruthenium(II) cation. Stereoretentive synthesis of tris chelates and their characterization: metal oxidation, ligand reduction, and spectroelectrochemical correlation. Inorg. Chem. 22, 2825–2832 (1983).

    Article  CAS  Google Scholar 

  46. Ghosh, P. et al. Introducing a new azoaromatic pincer ligand. Isolation and characterization of redox events in its ferrous complexes. Inorg. Chem. 53, 4678–4686 (2014).

    Article  CAS  Google Scholar 

  47. Evans, D. F. 400. The determination of the paramagnetic susceptibility of substances in solution by nuclear magnetic resonance. J. Chem. Soc. 2003–2005 (1959).

  48. Prakash, S. et al. Intrinsic hydrophilic nature of epitaxial thin-film of rare-earth oxide grown by pulsed laser deposition. Nanoscale 10, 3356–3361 (2018).

    Article  CAS  Google Scholar 

  49. Sarkar, T. et al. The effect of oxygen vacancies on water wettability of transition metal based SrTiO3 and rare-earth based Lu2O3. RSC Adv. 6, 109234–109240 (2016).

    Article  CAS  Google Scholar 

  50. Santos, G., Cavallari, M. R., Fonseca, F. J. & Pereira, L. Oxygen plasma surface treatment onto ITO surface for OLEDs based on europium complex. J. Integr. Circuits Systems 10, 7–12 (2015).

    Article  Google Scholar 

  51. Wu, C., Wu, C., Sturm, J. C. & Kahn, A. Surface modification of indium tin oxide by plasma treatment: an effective method to improve the efficiency, brightness, and reliability of organic light emitting devices. Appl. Phys. Lett. 70, 1348–1350 (1997).

    Article  CAS  Google Scholar 

  52. Yuan, Y. et al. Ultra-high mobility transparent organic thin film transistors grown by an off-centre spin-coating method. Nat. Commun. 5, 3005 (2014).

    Article  Google Scholar 

  53. Shi, X. & Zhao, Y.-P. Comparison of various adhesion contact theories and the influence of dimensionless load parameter. J. Adhes. Sci. Technol. 18, 55–68 (2004).

    Article  CAS  Google Scholar 

  54. Han, J. et al. Surface energy approach and AFM verification of the (CF)n treated surface effect and its correlation with adhesion reduction in microvalves. J. Micromech. Microeng. 19, 085017 (2009).

    Article  Google Scholar 

  55. Johnson, K., Kendall, K. & Roberts, A. Surface energy and the contact of elastic solids. Proc. R. Soc. Lond. A 324, 301–313 (1971).

    Article  CAS  Google Scholar 

  56. Derjaguin, B., Muller, V. & Toporov, Y. P. Effect of contact deformations on the adhesion of particles. Prog. Surf. Sci. 45, 131–143 (1994).

    Article  Google Scholar 

  57. Muller, V., Derjaguin, B. & Toporov, Y. P. On two methods of calculation of the force of sticking of an elastic sphere to a rigid plane. Colloids Surf. 7, 251–259 (1983).

    Article  CAS  Google Scholar 

  58. Celano, U. et al. Evaluation of the electrical contact area in contact-mode scanning probe microscopy. J. Appl. Phys. 117, 214305 (2015).

    Article  Google Scholar 

  59. Mayer, M. SIMNRA, a simulation program for the analysis of NRA, RBS and ERDA. In 15th International Conference on the Application of Accelerators in Research and Industry 541–544 (AIP, 1999).

  60. Feldman, L. C. & Mayer, J. W. Fundamentals of Surface and Thin Film Analysis. (North Holland, 1986).

  61. Kresse, G. & Hafner, J. Ab initio molecular-dynamics for liquid-metals. Phys. Rev. B 47, 558–561 (1993).

    Article  CAS  Google Scholar 

  62. Perdew, J. P., Burke, K. & Ernzerhof, M. Generalized gradient approximation made simple. Phys. Rev. Lett. 78, 3865–3868 (1996).

    Article  Google Scholar 

  63. Blochl, P. E. Projector augmented-wave method. Phys. Rev. B 50, 17953–17979 (1994).

    Article  CAS  Google Scholar 

Download references


We thank A. Castiñeiras for solving crystal structures, S. Kumar for helpful discussions on the mathematical modelling, A. Tempez for discussions regarding c-AFM measurements and M. Lal for helping with the nanostructure. T.V. and Sreetosh Goswami acknowledge support from NRF-CRP15-2015-01. Sreetosh Goswami thanks the NGS for funding support. Sreebrata Goswami acknowledges the financial support from SERB, India through grants SR/S2/JCB-09/2011 and EMR/2014/000520. D.T. thanks Science Foundation Ireland (SFI) for support (awards number 15/CDA/3491 and 12/RC/2275_P2) and for computing resources at the SFI/Higher Education Authority Irish Center for High-End Computing (ICHEC). C.A.N. acknowledges the Ministry of Education (MOE) for supporting this research under award no. MOE2015-T2-2-134.

Author information

Authors and Affiliations



Sreetosh Goswami devised the project and designed the experiments. Sreetosh Goswami performed the electrical and in situ spectroscopic measurements. S.P.R. and R.P. carried out the chemical synthesis and characterization under the supervision of Sreebrata Goswami. S. Hooda performed the RBS measurements. B.R.I. fabricated the nanopatterns. D.T. performed the theoretical calculations. M.A. performed the c-AFM measurements. R.S.W. developed the mathematical model. Sreetosh Goswami, R.S.W., T.V., Sreebrata Goswami, J.M., D.T., S. Hedström and S.S. performed data analysis. C.A.N. participated in discussions. Sreetosh Goswami, R.S.W., D.T., Sreebrata Goswami, J.M. and T.V. wrote the paper.

Corresponding authors

Correspondence to Sreetosh Goswami, Damien Thompson, Jens Martin, Sreebrata Goswami or T. Venkatesan.

Ethics declarations

Competing interests

The authors declare no competing interests.

Additional information

Peer review information Nature Nanotechnology thanks Alec Talin and the other, anonymous, reviewer(s) for their contribution to the peer review of this work.

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

Extended data

Extended Data Fig. 1 Multiple repeated traces.

500 repeated J(V) traces obtained from (a) structure A, (b) structure B and (c) structure C. The translucent cloud is the overlap of all the traces and the solid lines show one representative characteristic. The spread of the cloud indicates the maximum current variation in different traces which are orders of magnitude smaller than the conductance differences between the plateaus.

Extended Data Fig. 2 Non-volatility of the three states.

Grey curve: J(V) for full voltage sweep. Blue curve: J(V) with the forward scan stopped at the positive intermediate plateau (that is, V<V2, see Fig. 2) demonstrating that 11-state is robust and readable. Red curve: J(V) with the backward scan stopped in the negative intermediate plateau (that is, V>V4, see Fig. 2). This proves that the intermediate state is stable, and our device can be used both as binary or ternary memristors, that is both the upper and lower memristive loops can be used for (a) structure A, (b) structure B and (c) structure C. Arrows indicate the direction of the voltage sweep.

Extended Data Fig. 3 Effect of nano structures.

The J(V)s obtained for structure A, B and C are plotted in the same scale to visually illustrate the effect of nano structures in reducing switching voltage by ~30 times and increasing switching current by ~ 6 orders of magnitude.

Extended Data Fig. 4 Endurance.

a Response of structure B to pulses with 30 ns rise time. The current overshoot indicates that the switching time is <30 ns. b Endurance of structure B over ~1010 cycles measured with pulses as shown in (a) showing no indication of any degradation.

Extended Data Fig. 5 Retention and stability.

a, Pulse test to prove retention of structure B at 0 V. After writing, reading operations were performed after 1 hour, 2 hours and 2 days with the written state intact. b, Stability of individual conductance states: Three devices (structure B) with the same dimensions were fabricated and set into three different conductance states: 00 (on), 11 (intermediate), and 31 (off). All devices were measured simultaneously with constant application of read voltage V=500 mV at 350 K.

Extended Data Fig. 6 Top and bottom electrode variation.

The qualitatively similar J(V) response of the film in different electrode combinations, viz. (a) Pt/film/Pt, (b) Au/film/Pt, (c) Au/film/Au proving that the switching phenomenon is not an interface-specific phenomenon. The switching with noble metal electrodes also excludes the role of atomic/ ionic migration of the electrode materials in our observed switching.

Extended Data Fig. 7 Device characteristics with ITO top electrode.

The J(V) of devices with ITO as the top electrode for (a) structure A and (b) structure B. These structures are used for performing in-situ spectroscopic measurements. The current levels are similar to Au/film/ITO structure with small differences in switching voltage values due to the different work function of ITO. Consistent with redox mechanism, because of lower work function of ITO compared to Au, the switch-on voltage values with ITO top electrode increase whereas the switch-off voltages decrease.

Supplementary information

Supplementary Information

Supplementary Figs. S1–S38, Tables S1–S5 and refs. 1–39.

Rights and permissions

Springer Nature or its licensor (e.g. a society or other partner) holds exclusive rights to this article under a publishing agreement with the author(s) or other rightsholder(s); author self-archiving of the accepted manuscript version of this article is solely governed by the terms of such publishing agreement and applicable law.

Reprints and Permissions

About this article

Check for updates. Verify currency and authenticity via CrossMark

Cite this article

Goswami, S., Rath, S.P., Thompson, D. et al. Charge disproportionate molecular redox for discrete memristive and memcapacitive switching. Nat. Nanotechnol. 15, 380–389 (2020).

Download citation

  • Received:

  • Accepted:

  • Published:

  • Issue Date:

  • DOI:

This article is cited by


Quick links

Find nanotechnology articles, nanomaterial data and patents all in one place. Visit Nano by Nature Research