Stable Metallic Enrichment in Conductive Filaments in TaOx-Based Resistive Switches Arising from Competing Diffusive Fluxes

Yuanzhi Ma, Jonathan M. Goodwill, Dasheng Li, David A. Cullen, Jonathan D. Poplawsky, Karren L. More, James A. Bain, Marek Skowronski

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33 Scopus citations

Abstract

Oxide-based resistive-switching devices hold promise for solid-state memory technology. Information encoding is accomplished by electrically switching the device between two nonvolatile states with low and high resistance states (LRS/HRS). It is generally accepted that the change between these states is due to the motion of oxygen vacancies forming a continuous (LRS) or gapped (HRS) filament between the electrodes. Direct assessments of filaments are rare due to their small size and the difficulty of locating the filament. Electron microscopy experiments reveal the filament structure and chemistry in TaO2.0 ± 0.2-based 150 × 150 nm2 devices with cross-sectional geometry after forming with power dissipation lower than 1 mW. The filaments appear to be roughly hourglass-shaped with a diameter of less than 10 nm and are composed of Ta-rich and O-poor mostly amorphous material with local compositions as Ta-rich as TaO0.4. The as-formed HRS has a gap up to 10 nm wide located next to the anode and composed of nearly stoichiometric TaO2.5. The tantalum and oxygen distribution is consistent with filaments formed by the motion of both Ta and O driven by temperature gradients (Soret effect) and an electric field. This interpretation points towards a new compact model of resistive-switching devices.

Original languageEnglish
Article number1800954
JournalAdvanced Electronic Materials
Volume5
Issue number7
DOIs
StatePublished - Jul 2019

Funding

The authors would like to acknowledge the useful discussions with Prof. J. LeBeau. This work was supported in part by NSF Grant No. DMR 1409068, and Data Storage Systems Center at Carnegie Mellon University. The authors acknowledge the use of the Materials Characterization Facility at Carnegie Mellon University supported by grant MCF-677785. The APT and electron microscopy experiments were conducted at ORNL’s Center for Nanophase Materials Sciences (CNMS), which is a U.S. DOE Office of Science user facility. This work made use of deposition facilities provided by ONR DURIP equipment Grant No. N000141310874. The authors would like to thank James Burns for atom probe sample preparation. Y.M. designed the experiments, tested the devices, prepared the TEM samples, conducted microscopy experiments, and contributed to interpretation and writing of the manuscript. J.M.G. and D.L. designed and fabricated the devices, D.A.C. and K.L.M. participated in microscopy experiments and their interpretation, J.D.P. conducted the atom probe experiments and interpreted the APT data. J.A.B. and M.S. designed the overall concept of experiments and simulations and contributed toward writing of the manuscript. The authors would like to acknowledge the useful discussions with Prof. J. LeBeau. This work was supported in part by NSF Grant No. DMR 1409068, and Data Storage Systems Center at Carnegie Mellon University. The authors acknowledge the use of the Materials Characterization Facility at Carnegie Mellon University supported by grant MCF-677785. The APT and electron microscopy experiments were conducted at ORNL's Center for Nanophase Materials Sciences (CNMS), which is a U.S. DOE Office of Science user facility. This work made use of deposition facilities provided by ONR DURIP equipment Grant No. N000141310874. The authors would like to thank James Burns for atom probe sample preparation. Y.M. designed the experiments, tested the devices, prepared the TEM samples, conducted microscopy experiments, and contributed to interpretation and writing of the manuscript. J.M.G. and D.L. designed and fabricated the devices, D.A.C. and K.L.M. participated in microscopy experiments and their interpretation, J.D.P. conducted the atom probe experiments and interpreted the APT data. J.A.B. and M.S. designed the overall concept of experiments and simulations and contributed toward writing of the manuscript.

Keywords

  • Soret effect
  • electroformation
  • field-driven diffusion
  • filaments
  • resistive switching

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