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Formation of the Conducting Filament in TaOx-Resistive Switching Devices by Thermal-Gradient-Induced Cation Accumulation

Journal Article · · ACS Applied Materials and Interfaces
 [1];  [1];  [2];  [3];  [3];  [3];  [1];  [4];  [1]
  1. Carnegie Mellon Univ., Pittsburgh, PA (United States). Dept. of Materials Science and Engineering
  2. National Inst. of Standards and Technology (NIST), Gaithersburg, MD (United States)
  3. Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)
  4. Carnegie Mellon Univ., Pittsburgh, PA (United States). Dept. of Electrical and Computer Engineering
Here, the distribution of tantalum and oxygen ions in electroformed and/or switched TaOx-based resistive switching devices has been assessed by high-angle annular dark-field microscopy, X-ray energy-dispersive spectroscopy, and electron energy-loss spectroscopy. The experiments have been performed in the plan-view geometry on the cross-bar devices producing elemental distribution maps in the direction perpendicular to the electric field. The maps revealed an accumulation of +20% Ta in the inner part of the filament with a 3.5% Ta-depleted ring around it. The diameter of the entire structure was approximately 100 nm. The distribution of oxygen was uniform with changes, if any, below the detection limit of 5%. We interpret the elemental segregation as due to diffusion driven by the temperature gradient, which in turn is induced by the spontaneous current constriction associated with the negative differential resistance-type I–V characteristics of the as-fabricated metal/oxide/metal structures. A finite-element model was used to evaluate the distribution of temperature in the devices and correlated with the elemental maps. In addition, a fine-scale (~5 nm) intensity contrast was observed within the filament and interpreted as due phase separation of the functional oxide in the two-phase composition region. Understanding the temperature-gradient-induced phenomena is central to the engineering of oxide memory cells.
Research Organization:
Oak Ridge National Laboratory (ORNL), Oak Ridge, TN (United States)
Sponsoring Organization:
Defense Advanced Research Projects Agency (DARPA); National Science Foundation (NSF); Semiconductor Research Corp. (SRC), Durham, NC (United States). Microelectronics Advanced Research Corp. (MARCO); USDOE Office of Science (SC), Basic Energy Sciences (BES) (SC-22). Scientific User Facilities Division
Grant/Contract Number:
AC05-00OR22725
OSTI ID:
1460170
Journal Information:
ACS Applied Materials and Interfaces, Journal Name: ACS Applied Materials and Interfaces Journal Issue: 27 Vol. 10; ISSN 1944-8244
Publisher:
American Chemical Society (ACS)Copyright Statement
Country of Publication:
United States
Language:
English

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Cited By (5)

Stable Metallic Enrichment in Conductive Filaments in TaO x ‐Based Resistive Switches Arising from Competing Diffusive Fluxes journal April 2019
Spontaneous current constriction in threshold switching devices journal April 2019
Metallic filamentary conduction in valence change-based resistive switching devices: the case of TaO x thin film with x ∼ 1 journal January 2019
Intrinsic current overshoot during thermal-runaway threshold switching events in TaO x devices journal July 2019
Nanoscale density variations in sputtered amorphous TaO x functional layers in resistive switching devices journal February 2020

Figures / Tables (7)


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