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

Journal Article · · ACS Applied Materials and Interfaces

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 Lab. (ORNL), Oak Ridge, TN (United States)
Sponsoring Organization:
USDOE Office of Science (SC), Basic Energy Sciences (BES). Scientific User Facilities Division; Semiconductor Research Corp. (SRC), Durham, NC (United States). Microelectronics Advanced Research Corp. (MARCO); Defense Advanced Research Projects Agency (DARPA); National Science Foundation (NSF)
Grant/Contract Number:
AC05-00OR22725; 1409068; MCF-677785
OSTI ID:
1460170
Journal Information:
ACS Applied Materials and Interfaces, Vol. 10, Issue 27; ISSN 1944-8244
Publisher:
American Chemical Society (ACS)Copyright Statement
Country of Publication:
United States
Language:
English
Citation Metrics:
Cited by: 28 works
Citation information provided by
Web of Science

References (52)

A fast, high-endurance and scalable non-volatile memory device made from asymmetric Ta2O5−x/TaO2−x bilayer structures journal July 2011
HfO x -Based Vertical Resistive Switching Random Access Memory Suitable for Bit-Cost-Effective Three-Dimensional Cross-Point Architecture journal February 2013
Characteristic electroforming behavior in Pt/TiO2/Pt resistive switching cells depending on atmosphere journal December 2008
Redox-Based Resistive Switching Memories - Nanoionic Mechanisms, Prospects, and Challenges journal July 2009
Direct Identification of the Conducting Channels in a Functioning Memristive Device journal June 2010
Transient Thermometry and High-Resolution Transmission Electron Microscopy Analysis of Filamentary Resistive Switches journal July 2016
Atomic structure of conducting nanofilaments in TiO2 resistive switching memory journal January 2010
Direct observation of microscopic change induced by oxygen vacancy drift in amorphous TiO2 thin films journal July 2010
Collective Motion of Conducting Filaments in Pt/n-Type TiO2/p-Type NiO/Pt Stacked Resistance Switching Memory journal March 2011
Improved endurance of resistive switching TiO 2 thin film by hourglass shaped Magnéli filaments journal June 2011
Anatomy of a Nanoscale Conduction Channel Reveals the Mechanism of a High-Performance Memristor journal November 2011
Direct evidence on Ta-Metal Phases Igniting Resistive Switching in TaOx Thin Film journal September 2015
Sub-10 nm Ta Channel Responsible for Superior Performance of a HfO2 Memristor journal June 2016
Direct Observation of Localized Radial Oxygen Migration in Functioning Tantalum Oxide Memristors journal February 2016
The mechanism of electroforming of metal oxide memristive switches journal May 2009
Elimination of high transient currents and electrode damage during electroformation of TiO 2 -based resistive switching devices journal September 2012
Conductive Filament Expansion in TaO x Bipolar Resistive Random Access Memory during Pulse Cycling journal November 2013
Oxygen migration during resistance switching and failure of hafnium oxide memristors journal March 2017
Reduction in the reset current in a resistive random access memory consisting of NiOx brought about by reducing a parasitic capacitance journal July 2008
Spectromicroscopy of tantalum oxide memristors journal June 2011
The switching location of a bipolar memristor: chemical, thermal and structural mapping journal May 2011
Characterization of electroforming-free titanium dioxide memristors journal January 2013
Synergistic Resistive Switching Mechanism of Oxygen Vacancies and Metal Interstitials in Ta 2 O 5 journal January 2016
In situ observation of filamentary conducting channels in an asymmetric Ta2O5−x/TaO2−x bilayer structure journal September 2013
Microscopy study of the conductive filament in HfO2 resistive switching memory devices journal September 2013
Probing nanoscale oxygen ion motion in memristive systems journal May 2017
Thermophoresis/diffusion as a plausible mechanism for unipolar resistive switching in metal–oxide–metal memristors journal March 2012
Electron energy-loss spectroscopy in the TEM journal December 2008
Structural and chemical characterization of TiO 2 memristive devices by spatially-resolved NEXAFS journal October 2009
Dynamic Evolution of Conducting Nanofilament in Resistive Switching Memories journal July 2013
A Phenomenological Model for the Reset Mechanism of Metal Oxide RRAM journal December 2010
Physical electro-thermal model of resistive switching in bi-layered resistance-change memory journal April 2013
Comprehensive Physical Model of Dynamic Resistive Switching in an Oxide Memristor journal February 2014
Isothermal Switching and Detailed Filament Evolution in Memristive Systems journal April 2014
The Migration of Metal and Oxygen during Anodic Film Formation journal January 1965
The Measurement of Ionic Mobilities in the Anodic Oxides of Tantalum and Zirconium by a Precision Sectioning Technique journal January 1968
Nanoscale cation motion in TaOx, HfOx and TiOx memristive systems journal September 2015
Graphene-Modified Interface Controls Transition from VCM to ECM Switching Modes in Ta/TaO x Based Memristive Devices journal September 2015
Electronic Instabilities Leading to Electroformation of Binary Metal Oxide-based Resistive Switches journal July 2014
Electro-Thermal Model of Threshold Switching in TaO x -Based Devices journal March 2017
Switching mechanism in two-terminal vanadium dioxide devices journal March 2015
Joule Heating-Induced Metal–Insulator Transition in Epitaxial VO 2 /TiO 2 Devices journal May 2016
Specific Negative Resistance in Solids journal December 1963
Switching dynamics of TaO x -based threshold switching devices journal March 2018
Compositional tailoring of the thermal expansion coefficient of tantalum (V) oxide journal February 2006
Thermal Diffusion in Crystalline Solids journal December 1967
Morphological and electrical changes in TiO 2 memristive devices induced by electroforming and switching: Morphological and electrical changes in TiO 2 memristive devices journal November 2009
Observation of conducting filament growth in nanoscale resistive memories journal January 2012
Electrochemical dynamics of nanoscale metallic inclusions in dielectrics journal June 2014
Direct Observation of Conversion Between Threshold Switching and Memory Switching Induced by Conductive Filament Morphology journal July 2014
Origin of the Ultra-nonlinear Switching Kinetics in Oxide-Based Resistive Switches journal September 2011
Thermometry of Filamentary RRAM Devices journal September 2015

Cited By (5)

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

Figures / Tables (7)