Opto-Ionics for Memristive Switching in Lithium Titanate

Fran Kurnia^a, Drew Buzzell^b, Thomas Defferriere^c, Lukas Wolz^d^,^e, Yang Wang^f, Johanna Eichhorn^d^,^e, Harry Tuller^c, Bettina Lotsch^f, Jennifer Rupp^a^,^g

^aDepartment of Chemistry, Technical University of Munich, 85748 Garching, Germany

^bDepartment of Electrical Engineering and Computer Science, Massachusetts Institute of Technology, Cambridge, MA 02139, USA

^cDepartment of Materials Science and Engineering, Massachusetts Institute of Technology, Cambridge, MA 02139, USA

^dWalter-Schottky-Institute, Technical University of Munich, 85748 Garching, Germany

^eDepartment of Physics, Technical University of Munich, 85748 Garching, Germany

^fNanochemistry Department, Max Planck Institute for Solid State Research, Heisenbergstraße 1, 70569 Stuttgart, Germany

^gTUMint Energy Research, Technical University of Munich, 85748 Garching, Germany

Proceedings of 24th International Conference on Solid State Ionics (SSI24)

Devices for a Net Zero World

London, United Kingdom, 2024 July 14th - 19th

Organizers: John Kilner and Stephen Skinner

Oral, Fran Kurnia, presentation 363
Publication date: 10th April 2024

Neuromorphic computing and memory devices using memristive effects have the potential to contribute fast and non-binary computing beyond transistors. Lithium based oxides like lithium titanate (i.e., spinel Li4Ti5O12) provide ample opportunities to switch resistively due to the strong electronic state-lithiation coupling and multiple phases existent beyond their typical use in battery anodes.[1,2] Recently, it was demonstrated that above band gap illumination could lead to enhancement of ionic transport in doped binary oxides by modulating space charge barriers at grain boundaries.[3] In this work we employ photoconductive Atomic Force Microscopy (phAFM) and observe photocurrent generation, consistent with the presence of space charge layers at interfaces in lithium titanate thin films. Phototitration measurement at varied bias voltage reveals the existence of a memristive effect, and that the current is much more rapidly generated upon switching under the 375 nm light illumination. Furthermore, we test the memristive switching characteristics between dark and under illumination for cross-bar measurements up to 200 kV/cm. The memristive device shows a noticeable difference under the dark vs. light; the photomemristive behavior shows a gradual increase of current with time with a concomitant decrease in device resistance. Collectively, we demonstrate an opto-ionic effect for lithium titanate films allowing for memristive operation with a wider range of read/write options for next-generation opto-memristor devices.

References:

[1] Gonzalez-Rosillo, J. C., Balaish, M., Hood, Z. D., et al. Lithium-Battery anode gains additional functionality for neuromorphic computing through metal–insulator phase separation. Adv. Mater. 2020, 32, 1907465.

[2] Zhu, Y., Gonzalez-Rosillo, J.C., Balaish, M. et al. Lithium-film ceramics for solid-state lithionic devices. Nat. Rev. Mater. 2021, 6, 313–331.

[3] Defferriere, T., Klotz, D., Gonzalez-Rosillo, J.C. et al. Photo-enhanced ionic conductivity across grain boundaries in polycrystalline ceramics. Nat. Mater. 2022, 21, 438–444.

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