STM-induced reversible switching of local conductivity in thin<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mrow><mml:msub><mml:mrow><mml:mi mathvariant="normal">Al</mml:mi></mml:mrow><mml:mrow><mml:mn>2</mml:mn></mml:mrow></mml:msub></mml:mrow><mml:mrow><mml:msub><mml:mrow><mml:mi mathvariant="normal">O</mml:mi></mml:mrow><mml:mrow><mml:mn>3</mml:mn></mml:mrow></mml:msub></mml:mrow></mml:math>films

Metal-insulator-metal (MIM) tunnel junctions with the aluminum oxide tunnel barriers confined between cobalt electrodes exhibit less resistance drift over time than junctions that utilize a thick, unconfined aluminum electrode. The improved long time stability is attributed to better initial oxide quality achieved through confinement (use of a potential energy well for the oxygen) and plasma oxidation. In this work, Co/AlOx/Co and Co/Al/AlOx/Co tunnel junction aging is compared over a period of approximately 9 months using transport measurements and Wentzel-Kramers-Brillouin (WKB) based modelling. The Co/AlOx/Co (confined) tunnel junction resistance increased by (32 ± 6) % over 5400 h, while Co/Al/AlOx/Co (unconfined) tunnel junction resistance increased by (85 ± 23) % over 5200 h. Fit parameters for the tunnel barrier width and potential energy barriers were extracted using WKB transport modelling. These values change only a small amount in the confined Co/AlOx/Co tunnel junction but show a significant drift in the unconfined Co/AlOx/Co tunnel junction.

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“…These barrier heights and width values show good agreement with the literature for similar Co/AlOx/Co tunnel junctions. 17,33,34 …”

Section: Methodsmentioning

confidence: 99%

Reduced resistance drift in tunnel junctions using confined tunnel barriers

Barcikowski

Pomeroy

2017

Journal of Applied Physics

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“…However, both effects were found to be irreversible. By carefully tuning the film thickness and the scanning parameters, Kurnosikov et al were finally able to perform intentional reversible switching events, considered a precursor of soft breakdown, between different conductance states in Al2O3 [77].…”

Section: Scanning Tunneling Microscopy For the Investigation Of Resismentioning

confidence: 99%

Probing electrochemistry at the nanoscale: in situ TEM and STM characterizations of conducting filaments in memristive devices

et al. 2017

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Correspondence to: yuchaoyang@pku.edu.cn (Y.Y.), y-taka@ist.hokudai.ac.jp (Y.T.), arita@nano.ist.hokudai.ac.jp (M.A.), m.moors@fz-juelich.de (M.M.), a.kenyon@ucl.ac.uk (A.J.K.)Abstract Memristors or memristive devices are two-terminal nanoionic systems whose resistance switching effects are induced by ion transport and redox reactions in confined spaces down to nanometre or even atomic scales. Understanding such localized and inhomogeneous electrochemical processes is a challenging but crucial task for continued applications of memristors in nonvolatile memory, reconfigurable logic, and brain inspired computing. Here we give a survey for two of the most powerful technologies that are capable of probing the resistance switching mechanisms at the nanoscaletransmission electron microscopy, especially in situ, and scanning tunneling microscopy, for memristive systems based on both electrochemical metallization and valence changes. These studies yield rich information about the size, morphology, composition, chemical state and 2 growth/dissolution dynamics of conducting filaments and even individual metal nanoclusters, and have greatly facilitated the understanding of the underlying mechanisms of memristive switching.Further characterization of cyclic operations leads to additional insights into the degradation in performance, which is important for continued device optimization towards practical applications.Resistive Random Access Memories (ReRAMs), or memristors [1], have tremendous potential for applications in nonvolatile embedded or storage class memories [2, 3], as well as in-memory logic that overcomes the von Neumann bottleneck [4]. They are also envisaged to form the basis of power-efficient neuromorphic systems by implementing plasticity similar to that of biological synapses [5]. Consequently, extensive efforts have been devoted to research into this novel class of devices, including studies of switching materials, device structures, scalability, integration, and so on.In particular, it is very important to understand the fundamental operation mechanisms of ReRAM in order to guide device-related studies. It is well known that the resistance switching effects in memristors are usually modulated by ionic transport and subsequent conducting filament formation/dissolution processes occurring at dimensions around 10 nm, and even down to atomic scales [6][7][8], hence elucidating the switching mechanisms requires advanced characterization techniques capable of resolving the nanoscale switching regions formed randomly in the devices.Here we give a survey of two of the most important technologies in understanding the switching mechanisms of ReRAMtransmission electron microscopy (TEM), especially when applied in situ, and scanning tunneling microscopy (STM). We will discuss the principles and designs behind these techniques, and show how they have furthered the understanding of the nature and dynamic evolution of conductive filaments. Finally, the remaining challenges in the understanding of memristive mechanisms w...

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“…The negative differential resistance phenomenon was observed in anodic Al 2 O 3 under vacuum condition, several decades ago [15]. Recently, the Al 2 O 3 film has been found to show reversible resistive switching characteristics [16][17][18][19][20]. Many switching mechanisms for Al 2 O 3 -based devices have been proposed, and most of studies suggest that the resistive switching behavior derives from the formation and rupture of conducting filaments [4,10,21,22].…”

Section: Introductionmentioning

confidence: 99%

Memristive behavior of Al2O3 film with bottom electrode surface modified by Ag nanoparticles

2014

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The memristive behavior of Al 2 O 3 -based device is significantly improved by introducing Ag nanoparticles (NPs). Inserting Ag NPs can effectively reduce the switching voltages, increase the resistance ratio (about 10 4 ) and enhance the sweep endurance (300 cycles). In particular, the stable switching properties are obtained by inserting an Ag NPs layer with an average diameter of 14 nm on the surface of bottom electrode, and the devices show a long retention time (more than 10 6 s) compared with the devices without Ag NPs. The switching mechanism is related to the oxygen-vacancy-based conducting filaments and the interfacial effect. The local enhancement and nonuniform distribution of electric field have the benefits to promote, induce and modulate the growth of conducting filaments, such as shape, location and orientation, which are responsible for the improvement performance of the devices.

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STM-induced reversible switching of local conductivity in thinAl2O3films

Cited by 19 publications

References 16 publications

Reduced resistance drift in tunnel junctions using confined tunnel barriers

Reduced resistance drift in tunnel junctions using confined tunnel barriers

Probing electrochemistry at the nanoscale: in situ TEM and STM characterizations of conducting filaments in memristive devices

Memristive behavior of Al2O3 film with bottom electrode surface modified by Ag nanoparticles

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