Correlation between Electronic Structure, Microstructure, and Switching Mode in Valence Change Mechanism Al2O3/TiOx‐Based Memristive Devices

Advanced Electronic Materials, vol. 9

Abstract

Abstract Memristive devices with valence change mechanism (VCM) show promise for neuromorphic data processing, although emulation of synaptic behavior with analog weight updates remains a challenge. Standard filamentary and area‐dependent resistive switching exhibit characteristic differences in the transition from the high to low resistance state, which is either abrupt with inherently high variability or gradual and allows quasi‐analog operation. In this study, the two switching modes are clearly correlated to differences in the microstructure and electronic structure for Pt/Al2O3/TiOx/Cr/Pt devices made from amorphous layers of 1.2 nm Al2O3 and 7 nm TiOx by atomic layer deposition. For the filamentary mode, operando spectromicroscopy experiments identify a localized region of ≈50 nm in diameter of reduced titania surrounded by crystalline rutile‐like TiO2, highlighting the importance of Joule heating for this mode. In contrast, both oxide layers remain in their amorphous state for the interfacial mode, which proves that device temperature during switching stays below 670 K, which is the TiO2 crystallization temperature. The analysis of the electronic conduction behavior confirms that the interfacial switching occurs by modulating the effective tunnel barrier width due to accumulation and depletion of oxygen vacancies at the Al2O3/TiOx interface. The results are transferable to other bilayer stacks.

Authors 11

1. Stephan Aussen Aachen

   Forschungszentrum Jülich · Jülich Aachen Research Alliance · RWTH Aachen University

   Affiliation as printed

   Peter Grünberg Institut (PGI 7 and 10) and JARA‐FIT Forschungszentrum Jülich GmbH Wilhelm‐Johnen‐Straße 52428 Jülich Germany

   RWTH Aachen University Templergraben 55 52062 Aachen Germany

   Peter Grünberg Institut (PGI 7 and 10) and JARA‐FIT Forschungszentrum Jülich GmbH Wilhelm‐Johnen‐Straße 52428 Jülich Germany

2. Felix Cüppers

   Forschungszentrum Jülich · Jülich Aachen Research Alliance

   Affiliation as printed

   Peter Grünberg Institut (PGI 7 and 10) and JARA‐FIT Forschungszentrum Jülich GmbH Wilhelm‐Johnen‐Straße 52428 Jülich Germany

3. Carsten Funck

   Forschungszentrum Jülich · Jülich Aachen Research Alliance

   Affiliation as printed

   Peter Grünberg Institut (PGI 7 and 10) and JARA‐FIT Forschungszentrum Jülich GmbH Wilhelm‐Johnen‐Straße 52428 Jülich Germany

4. Janghyun Jo

   Forschungszentrum Jülich · Ernst Ruska Centre

   Affiliation as printed

   Ernst Ruska‐Center (ERC‐1 / PGI‐5) and JARA‐FIT Forschungszentrum Jülich GmbH Wilhelm‐Johnen‐Straße 52428 Jülich Germany

5. Stephan Werner

   Helmholtz-Zentrum Berlin für Materialien und Energie

   Affiliation as printed

   Department X‐ray Microscopy Helmholtz‐Zentrum für Materialien und Energie GmbH Albert‐Einstein‐Str. 15 12489 Berlin Germany

6. Christoph Pratsch

   Helmholtz-Zentrum Berlin für Materialien und Energie

   Affiliation as printed

   Department X‐ray Microscopy Helmholtz‐Zentrum für Materialien und Energie GmbH Albert‐Einstein‐Str. 15 12489 Berlin Germany

7. Stephan Menzel

   Forschungszentrum Jülich · Jülich Aachen Research Alliance

   Affiliation as printed

   Peter Grünberg Institut (PGI 7 and 10) and JARA‐FIT Forschungszentrum Jülich GmbH Wilhelm‐Johnen‐Straße 52428 Jülich Germany

8. Regina Dittmann

   Forschungszentrum Jülich · Jülich Aachen Research Alliance

   Affiliation as printed

   Peter Grünberg Institut (PGI 7 and 10) and JARA‐FIT Forschungszentrum Jülich GmbH Wilhelm‐Johnen‐Straße 52428 Jülich Germany

9. Rafal E. Dunin‐Borkowski

   Forschungszentrum Jülich · Ernst Ruska Centre

   Affiliation as printed

   Ernst Ruska‐Center (ERC‐1 / PGI‐5) and JARA‐FIT Forschungszentrum Jülich GmbH Wilhelm‐Johnen‐Straße 52428 Jülich Germany

10. Rainer M. Waser Aachen Institute of Materials in Electrical Engineering and Information Technology II

    Forschungszentrum Jülich · Jülich Aachen Research Alliance · RWTH Aachen University

    Affiliation as printed

    Institute of Materials in Electrical Engineering and Information Technology II RWTH Aachen University Sommerfeldstraße 24 52074 Aachen Germany

    Peter Grünberg Institut (PGI 7 and 10) and JARA‐FIT Forschungszentrum Jülich GmbH Wilhelm‐Johnen‐Straße 52428 Jülich Germany

11. Susanne Hoffmann‐Eifert corresponding

    Forschungszentrum Jülich · Jülich Aachen Research Alliance

    Affiliation as printed

    Peter Grünberg Institut (PGI 7 and 10) and JARA‐FIT Forschungszentrum Jülich GmbH Wilhelm‐Johnen‐Straße 52428 Jülich Germany