Abstract
Oxygen ions’ migration is the fundamental resistive switching (RS) mechanism of the binary metal oxides-based memristive devices, and recent studies have found that the RS performance can be enhanced through appropriate oxygen plasma treatment (OPT). However, the lack of experimental evidence observed directly from the microscopic level of materials and applicable understanding of how OPT improves the RS properties will cause significant difficulties in its further application. In this work, we apply scanning probe microscope (SPM)-based techniques to study the OPT-enhanced RS performance in prototypical HfOx based memristive devices through in situ morphology and electrical measurements. It is first found that the structural deformations in HfOx nanofilm induced by migration of oxygen ions and interfacial electrochemical reactions can be recovered by OPT effectively. More importantly, such structural deformations no longer occur after OPT due to the strengthening in lattice structure, which directly illustrates the enhanced quantity of HfOx nanofilm and the nature of enhanced RS properties after OPT. Finally, the underlying mechanisms of OPT-enhanced RS performance are analyzed by the results of X-ray photoelectron spectroscopic (XPS) surface analysis. In the OPT-enhanced HfOx nanofilm, oxygen vacancies in crystalline regions can be remarkably reduced by active oxygen ions’ implantation. The oxygen ions transport will depend considerably on the grain boundaries and OPT-enhanced lattice structure will further guarantee the stability of conductive filaments, both of which ensure the uniformity and repeatability in RS processes. This study could provide a scientific basis for improving RS performance of oxides-based memristive devices by utilizing OPT.
Highlights
With the emergence of big data, cloud computing, the internet of things and artificial intelligence technology, the amount of information that needs to be stored and analyzed is exploding
The conductive atomic force microscopy (C-AFM) measurements were performed by utilizing a Ti/Ir coated conductive tip in contact mode as a top microelectrode, as shown in the insert part of Figure 2a
We directly observed the recovery phenomenon of structural deformations induced by migration of oxygen ions and interfacial electrochemical reactions in hafnium oxide (HfOx) nnaofilm after oxygen plasma treatment (OPT) through in situ scanning probe microscope (SPM) technologies
Summary
With the emergence of big data, cloud computing, the internet of things and artificial intelligence technology, the amount of information that needs to be stored and analyzed is exploding. As the mainstream in current semiconductor memory market, flash memory has encountered serious challenges to further scaling down [1] Both industry and academia have exerted great efforts to explore appropriate candidates for the next-generation non-volatile memory (NVM) [2,3]. Several well-accepted filamentary switching mechanisms have been raised to understand the underlying principle of the RS behaviors. They are respectively electrochemical metallization mechanism (ECM), thermochemical mechanism (TCM), valence change mechanism (VCM) and threshold switching (TS) for selector devices [1]. The interfacial coupling mechanism (ICM) was introduced to explain the RS between HRS and LRS [8]
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