Laboratoire de lIntgration, du Matriau au Systme IMS UMR 5218

MOOREA Meeting, 02/25/2013

J.E. Lorival, T. Jacquet, C. Maneux 12OutlineSwitching mechanisms.Switching mechanisms in inorganic materials.Organic materials classification and switching mechanisms observed.Switching mechanisms discussions.Memristor modeling.Literature models analyses.Work in progress.

Switching mechanismsMOOREAFeb 25, 20132ContextLast years, several teams working on memristors.Ferromagnetic materials.Organic materials.Inorganic materials.Electrolytes, amorphous silicon, binary oxides.

Numerous materials : memristors, top/bottom electrodes.Substantial state of the art.Classification.Material, compound types.Resistive switching mechanisms.3

Switching mechanismsMOOREAFeb 25, 20133Switching mechanisms in inorganic materials [1] [2].Unipolar and bipolar switching behaviors.

Filament and interface types.

Classification of switching mechanisms4[1] Waser, Nature, 2007[2] Pan, Natural Science: Materials International 20(2010), 2010

FilamentInterface

UnipolarBipolar

Switching mechanismsMOOREAFeb 25, 20134Switching mechanisms, filament type [1/4]5Thermal effect : Joule heating unipolar behaviorFilaments created/restored by voltage breakdowns.Filaments broken with high currents by thermal dissolution.Materials: NiO, CuO, ZrO, HfO

Sawa, materialstoday, 2008, Vol. 11, no. 6

Memristors ModelSwitching mechanismsMOOREAFeb 25, 201356

[2] Pan, Natural Science: Materials International 20(2010), 2010Switching mechanismsSwitching mechanisms, filament type [2/4]

Ionic transport / redox processes bipolar behavior.Anions migration:Migration of oxygen vacancies VO+.Cations migration: electrochemical metallization (ECM).Migration of metal cations.Relative mature theory [2].MOOREAFeb 25, 201367Ionic transport / redox processes bipolar behaviorAnions migration : different mechanisms [3].(I): Oxygen vacancies VO+ form hopping conduction path (ZnO).SET: dielectric breakdown. Generation and drift of VO+ filaments.RESET: depletion of e- in VO+ along filaments.Recovery of the electron-depleted VO+ with O2-.[3] Xu, VLSI Technology, 2008

Left:Right:Switching mechanismsSwitching mechanisms, filament type [3/4]

MOOREAFeb 25, 20137

8Ionic transport / redox processes bipolar behaviorAnions migration : different mechanisms [4].(II): VO+ acting as dopants making the MO conductive (TiO).VO+ piling up near the cathode and trapping electrons.Metal valency reduced Generated filaments moving up to the anode.[4] Waser, Microelectronic Engeneering 86, 2009

Switching mechanismsSwitching mechanisms, filament type [4/4]

MOOREAFeb 25, 201389Interface type switching mechanism bipolar.Oxygen depleted zone near cathode due to VO+ diffusion (doping) [5]. Electron injection from electrode modified by barrier height change.Electrode materials, effects on contact resistance.Contact resistances control the switching mechanism.MIM, two interfaces. 1 Ohmic, 1 Schottky-like for switching.Barrier height: F(applied voltage ; material, electrodes energy bands).

[5] J. J. Yang, Nature Nanotechnology, Vol 3, July 2008

Switching mechanisms Switching mechanisms, interface type

MOOREAFeb 25, 20139Another mechanisms referred10Charge Transfert.Trapping/Detrapping Space Charge Limited Current (SCLC).Insulator-metal transition(IMT).Electronic charge injection acts as doping.Induce IMT in perovskite-type oxides : (Pr, Ca)MnO3, SrTiO3:Cr.Ferroelectric polarization.

Switching mechanismsMOOREAFeb 25, 201310

Organic materials11Classification in [6].Polymer MIM devices.Small-molecules MIM devices.Donor-acceptor complexes.Electrochemical systems.Nanoparticle blends.[6] Campbell Scott, Bozano, Nonvolatile Memory Elements Based on Organic Materials, Advanced Materials, 2007

Hystereses observed in organic materials based memristors. Investigation on the influence of the bottom electrode on the memristor performances (I-V) [BOZANO_2005]Switching mechanismsMOOREAFeb 25, 201311Switching mechanisms in organic materials12Some switching mechanisms reported in [6].Filament conduction.Ion transport / redox process.Trapping- Detrapping SCLC.Charge Transfer (CT).Conformational effects.

Organic and inorganic materials.Some switching mechanisms in common. => Yet with different driving mechanisms (drivers).

Two molecules with different conformations. The two molecules can be made identical with a rotation of 180 degree about the central single bond[6] Campbell, Bozano, Nonvolatile Memory Elements Based on Organic Materials, Advanced Materials, 2007Switching mechanismsMOOREAFeb 25, 201312Discussions and debates [1/2]13Switching mechanisms still under investigations.For a same switching mechanisms, various drivers.Driving mechanisms depending on both materials and electrodes.Electrodes impacts. Inorganic material: Cu electrodes with TiO2: Cu diffusion in TiO2 [7].Organic material: Aluminum electrode controls switching, not material [8]. Changing material state : different switching mechanisms.ZnO/Cu/ZnO: carriers trapping/detrapping redox after RTA [9].Several switching mechanisms occurring simultaneously.TiO2: thermal effects, metallic filament, VO+ migration, E fields.Unipolarity/bipolarity coexistence depending on CC [10].[7] Yang L, Appl. Phys. Lett., 2009[8] Colle, Organic Electronics 7, 2006[9] Yang T, Appl. Phys, 2009[10] Jeong, Electrochemical and Solid-State Letters, 2007Switching mechanismsMOOREAFeb 25, 201313Discussions and debates [2/2]14Switching mechanisms still under investigations.Numerous mechanisms observed but few conclusions.Not enough measurements that go beyond observations.Are the switching mechanisms observed in structures the right ones ?Several structure deteriorated after a set of measures.Fabrication processes currently not enough mature ?Cases where mechanisms are due to (un)desirable effects ?Electrode atoms diffusion in material, fabrication defaults, dustReproducibility of switching behaviors ?

PCzDPM -conjugated polyler bearing carbazole moieties. Park, J. Chem. Phys. Vol. 114, no. 32, 2010Switching mechanismsMOOREAFeb 25, 20131415OutlineSwitching mechanisms.Memristors modeling.Memristor models present in the literature.Linear ion drift, Simmons, TEAM models.Window functions for boundary conditions and ion drift profiles.Literature models analyses.Work in progress

Memristor modelsMOOREAFeb 25, 201315ContextFew models present in the literature.Dedicated to inorganic models.Most of them are based on the linear ion drift model [11] [12] [13] [14].Aims: Test the original model viability or improve/update it.Ref. [12]: saturation/depletion effects + lifetime.Ref. [14]: threshold voltages for bipolarity added.16[11] Strukov, Nature, vol 453, 2008[12] Sharifi, Journal Circuits, Systems ans Computers, Vol 19, no 2, 2010 [13] Batas, IEEE Trans. on Nanotechnology, Vol 10, no 2, 03/2011[14] Corinto, IEEE Trans. on Circuits and Systems, vol 59, no 11, 11/2012Other types of model found.Non linear ion drift model [15].Simmons tunneling barrier model [16].ThrEshold Adaptative Memristor (TEAM) model [17].[15] Chang, Appl. Phys. A, 2011[16] Pickett, J. Appl. Phys. 106, 2009[17] Kwatinsky, IEEE Trans. Circuits and systems, 2012 (not published)Memristor modelsMOOREAFeb 25, 201316FundamentalsMemristor mathematical definition given by Chua.Functional relation between charge and flux.

Basic mathematical definition for a current controlled memristor.17

w : [set of] state variables

Memristor modelsMOOREAFeb 25, 201317TiO2 HP memristor [1/2]Memristor behavior recognition at the nanoscale from HP [11].TiO2 binary oxide based inorganic memristor.Proposition of the linear ion drift model.18

Memristor models[11] Strukov, Nature, vol 453, 2008MOOREAFeb 25, 201318TiO2 HP memristor [2/2]Memristor behavior recognition at the nanoscale from HP [11].Simulations with the model, measurements with a test structure.Test structure : Pt/TiO2/Pt.19

Memristor models[11] Strukov, Nature, vol 453, 2008MOOREAFeb 25, 201319Memristor models characteristics [1/2] 20[17] Kwatinsky, IEEE Trans. Circuits and systems, 2012 (not published)

In [17].Memristor model types listedBasic version for the linear ion drift model.TEAM model proposition.Memristor modelsMOOREAFeb 25, 201320Memristor models characteristics [2/2] 21[17] Kwatinsky, IEEE Trans. Circuits and systems, 2012 (not published)

Memristor modelsMOOREAFeb 25, 201321Window functions requirementIn model description, boundary conditions needed.W can be smaller (higher) than 0 (D) wrong memristor values.22Window functions.Fix boundary conditions, w comprised exclusively in [0,D].Serve to model ion drift profile in the material.

Source: Prodromakis, IEEE Trans. Electron Device, vol 58, no 9, 09/2011D = 10nROFF = 16K RON = 100Memristor modelsMOOREAFeb 25, 201322Window functions in literature [1/3]Most known window functions listed in [17].23

[17] Kwatinsky, IEEE Trans. Circuits and systems, 2012 (not published)[18] Joglekar, European Journal of Physics, vol 30, no 4, 2009[19] Bioleck, radioengineering, vol 18, no 2, Part 2, 2009[20] Prodromakis, IEEE Trans. Electron Device, vol 58, no 9, 09/2011

[18][19][20]Memristor modelsMOOREAFeb 25, 201323Window functions in literature [2/3]Window functions Defined with the normalized value of D, w (or x) evolves between [0,1].Depend on a p parameter.p small : non linear ions drift profile function.p high : linear ions drift profile function.Linear model + non linear function non linear model.

24

Prodromakis

JoglekarBiolekMemristor modelsMOOREAFeb 25, 201324Window functions in literature [3/3]Joglekar window.When x=0 or x=D, state cannot be changed anymore.Works only for single-valued memristor.

Biolek window.Controls states for bipolarity behavior.Discontinuities for boundary conditions for high p.Works only for multi-valued memristor.

Prodromakis window.Parabolic function like Joglekar.Window function is scalable : F(x)max different from 1.

25

ProdromakisJoglekar & BiolekMemristor modelsMOOREAFeb 25, 201325Simmons tunneling barrier model [1/2]HP Team investigates deeper the Pt/TiO2/Pt memristor [21].More knowledge regarding the physical process in bipolar switching.Energy required to switch the device decreases exponentially when increasing current Pt/TiO2/Pt is non linear. Model evolution : linear ion drift Simmons tunneling barrier.Ions drift profile based on electric tunnel effect between two identical electrodes separated by a thin insulating film [22].Bipolarity controlled with threshold currents + boundary conditions.26[21] Pickett, Journal of Appl. Phys, 2009[22] Simmons, Journal of Appl. Phys, 1963

X

Memristor modelsMOOREAFeb 25, 201326Simmons tunneling barrier model [2/2]27Deep knowledge of switching mechanisms in TiO2.Physical model High accuracy degree.Model can only be applied to TiO2 structures.High complexity degree huge convergence problems.Asymmetric behaviors can be only observed.Asymmetric behavior when switching states time are different.

Kwatinsky et al. worked on a simplified version.Memristor modelsTEAM ModelMOOREAFeb 25, 201327

ThrEshold Adaptative Model (TEAM) [1/3]Simplified version of Simmons tunneling barrier model.Decomposition in two parts of the derivative function.(I) Bipolar switching controlled by threshold currents.(II) Window function, TEAM function.Doping concentration in the material when injecting a current.28Memristor models

Simmons modelTEAM modelMOOREAFeb 25, 201328ThrEshold Adaptative Model (TEAM) [2/3]Simplified version of Simmons tunneling barrier model.Decomposition in two parts of the derivative function.(I) Bipolar switching controlled by threshold currents.(II) Window function, TEAM function.Doping concentration in the material when injecting a current.29Memristor models

dx/dt directionwhen i>0dx/dt directionwhen i TEAM model linear ion drift model.When TEAM model fits Simmons one. => Asymmetric behaviors only.

or

I-V linear relationshipI-V non-linear relationshipMOOREAFeb 25, 20133031OutlineSwitching mechanims.Memristor modeling.Literature models analyses.Tests on some memristor models to check their robustness and their versatility.Different versions of the linear ion drift model, TEAM model.Performed by varying different parameters describing dw/dt and M(w).Work in progress.

Models analysesMOOREAFeb 25, 201331Memristor models chosen for test Some authors provide descriptions with their model.Kvatinsky : Verilog-A descriptions [23]. Linear, non-linear, Simmons, TEAM models.Joglekar, Biolek, Prodromakis, TEAM window functions.32Models analysesCurrent work : test the models robustness and versatility.Linear ion drift model with ideal window(Verilog-A).Linear model, enhanced version with threshold voltages (ELDO) [14].TEAM model fitting Simmons model with ideal window (Verilog-A).TEAM model fitting linear model with ideal window (Verilog-A).Simmons model : converge problems. Work-in-progress.[14] Corinto, IEEE Trans. on Circuits and Systems, vol 59, no 11, 11/2012[23] Kvatinsky, CCIT (Center for Communication and information Technologies) Reports, 2011 MOOREAFeb 25, 201332Linear ion drift modelIdeal window : bipolarity and w comprised in [0, D].F(w) = 0 for w = 0 and w = D, 1 otherwise => linear ion drift profile.33Models analyses

Model configuration.Sinusoidal input voltage Vsin : 500mV, F = 0,1Hz.Ron = 100 ; Roff = 16K ; D = 10nm ; v = 10e-14 m2 s-1 V-1.w(t0) = 0 ; // initial conditiondt = 5ms.Roff = 16k w = 0Ron = 100 w = 10nmRoff / Ron = 160MOOREAFeb 25, 201333Linear model, M(w)=f(Vin)34Models analysesModel configuration.Vsin : F = 0,1Hz. Ron = 100 ; Roff = 16K ; D = 10nm ; v = 10e-14 m2 s-1 V-1 ; w(t0) = 0 ; dt = 5ms.Vin = 250mVVin = 125mV

w = 0 Roff = 16k w = 0,9nm R= 1,5k

w = 0 Roff = 16k w = 0,29nm R = 11k Roff / Ron = 160

Roff / Ron = 160MOOREAFeb 25, 201334

w = 0 Roff = 16k w = 0,58nm R = 11,5k

Linear model, M(w)=f(D)35Models analysesModel configuration.Vsin : 500 mV, F = 0,1Hz. Ron = 100 ; Roff = 16K ; v = 10e-14 m2 s-1 V-1 ;w(t0) = 0 ; dt = 5ms.D = 10nmD = 20nmw = 0 Roff = 16k w = 10nm Ron = 100

Roff / Ron = 160

Roff / Ron = 160MOOREAFeb 25, 201335Linear model, behavior on multiple periodsBy applying sinusoidal voltage during several periods (10T).36Models analysesModel configuration.Sinusodal input voltage Vsin : 250mV, F = 0,1Hz.Ron = 100 ; Roff = 16K; D = 10nm, v = 10e-14 m2 s-1 V-1.w(t0) = 0 ; dt = 5ms.

Roff decreases

Rmin RonReproducibility problem due to robustness ?

Source: Yu, IEEE Trans. Electron Device, vol 58, no 8, 08/2011Does model integrate uncovered defects in TiO2 ?

MOOREAFeb 25, 201336Linear model, impact of Roff/Ron ratioMemristor responses when increasing Roff/Ron.37Models analysesModel configuration.Sinusodal input voltage Vsin : 125mV, F = 0,1Hz.Ron = 100 ; D = 10nm, v = 10e-14 m2 s-1 V-1.w(t0) = 0 ; dt = 5ms.

Roff/Ron = 80Roff/Ron = 120Roff/Ron = 160

Roff/Ron80120160wmin000M(wmin)8K12K16Kwmax7nm3,7nm2,9nmM(wmax)2,7K7K11KMOOREAFeb 25, 201337Linear model, impact of frequencyMemristor responses when increasing frequency.38Models analysesModel configuration.Sinusodal input voltage Vsin : 250mV, F = 0,1Hz.Ron = 100 ; Roff = 16K ; D = 10nm ; v = 10e-14 m2 s-1 V-1.w(t0) = 0 ; dt = 5ms.5F = 0,5Hz dt = 2ms.100F = 10Hz dt = 100us.

Roff/Ron = 160Like Roff/Ron, when F increases.=> ions have lower mobility.=> memristor resistor.

dt : parameter in Verilog-A code [23].dt given such as dt = T/1000 at least.[23] Kvatinsky, Kvatinsky, CCIT (Center for Communication and information Technologies) Reports, 2011

Analytical expressionVerilog-A translation in [22]MOOREAFeb 25, 201338Linear model robustnessRobustness of the model. Impact of the time step.39Models analysesModel configuration.Sinusodal input voltage Vsin : 250mV, F = 0,1Hz.Ron = 100 ; D = 10nm ; v = 10e-14 m2 s-1 V-1.w(t0) = 0 ; dt = 5ms.

Time step: 5ms

dt is a sensitive parameter in the model.Time step: 2,5msdt: 5msdt: 5ms

dt: 2,5msTime step: 5ms

Time step: 5msdt: 10msThe results are in agreement with the hystereses behaviors observed in literature when modifying parameters for a given configuration.What is the behavior which must be observed for the starting configuration ? MOOREAFeb 25, 201339How about the other linear models ? TEAM Model fitting the linear ion drift model.Same behaviors observed for the same configurations.40Models analyses[14] Corinto, IEEE Trans. on Circuits and Systems, vol 59, no 11, 11/2012Enhanced version proposed by [14].Window functions (bipolarity + boundary conditions) + (VthOFF, VthON).

Behavioral conditionWindow Functionx(t)MOOREAFeb 25, 201340Corintos linear model enhanced version [1/2]41Models analyses[14] Corinto, IEEE Trans. on Circuits and Systems, vol 59, no 11, 11/2012

Enhanced version proposed by [14].Window functions (bipolarity + boundary conditions) + (VthOFF, VthON).Model configuration.Vsin : 1V, F = 1Hz. Ron = 100 ; Roff = 6K ; D = 10nm ; v = 10e-14 m2 s-1 V-1 ; w(t0) = 1nm.Vth(off) = Vth(on) = 0.

MOOREAFeb 25, 201341Corintos linear model enhanced version [2/2]42Models analyses[14] Corinto, IEEE Trans. on Circuits and Systems, vol 59, no 11, 11/2012

Enhanced version proposed by [14].Window functions (bipolarity + boundary conditions) + (VthOFF, VthON).Beware of the time step !

Model configuration.Vsin : 1,95V, F = 1Hz. Ron = 100 ; Roff = 16K ; D = 10nm ; v = 10e-14 m2 s-1 V-1 ; w(t0) = 3,5nm ;Vth(off) = Vth(on) = 0,975V ;Simulation of 1 period (1s)Below a time step of 500us(2000 points)

Simulation of 1 period (1s)Below a time step of 1ms(1000 points) MOOREAFeb 25, 201342TEAM model (Simmons), expression of dx/dtTEAM model in Simmons configuration + ideal window.Linear and non linear relations exhibit the same behaviors.X : oxide (undoped) region length. 43Models analyses

Bipolar switching controlled with Threshold currents ioff and ionfoff(x) = fon(x) = F(x)F(x) =1 when 0 < x < D0 otherwiseMOOREAFeb 25, 201343TEAM model (Simmons), hysteresis behaviorAsymetric switching: OFF state slower than ON STATE.44Models analyses

Kvatinsky results

Model configuration.Sinusodal input voltage Vsin : 0,5V, F = 20MHz.Ron = 50 ; Roff = 1K ; D = 3nm ;Ion = -8,9uA ; Ioff = 115uA ; on = 10 ; off = 10 ;Kon = -4,68e-13 ; Koff = 1,46e-9 ;Xon = 0 ; Xoff = 3nm ;w(t0) = 0 ;dt = 50ps. Simulation on 3T = 150ns for time step = 185ps.X : 0 0,862.M : 50 640MOOREAFeb 25, 201344

TEAM model (Simmons), M(x) = f(Vin)45Models analyses

Model configuration.Sinusodal input voltage : F = 20MHz.Ron = 50 ; Roff = 1K ; D = 3nm ;Ion = -8,9uA ; Ioff = 115uA ; on = 10 ; off = 10 ;Kon = -4,68e-13 ; Koff = 1,46e-9 ; Xon = 0 ; Xoff = 3nm ;w(t0) = 0 ; dt = 50ps. Simulation on 3T = 150ns for time step = 105ps.X : 0 1M : 50 1KVin = 500mVVin = 1V

X : 0 0,862.M : 50 640MOOREAFeb 25, 201345

TEAM model (Simmons), M(x) = f(Roff)46Models analysesModel configuration.Sinusodal input voltage : F = 20MHz.Ron = 50 ; D = 3nm ;Ion = -8,9uA ; Ioff = 115uA ; on = 10 ; off = 10 ;Kon = -4,68e-13 ; Koff = 1,46e-9 ; Xon = 0 ; Xoff = 3nm ;w(t0) = 0 ; dt = 50ps. Simulation on 3T = 150ns for time step = 187ps.X : 0 1M : 50 1KVin = 1V, ROFF = 1K

Vin = 1V, ROFF = 5K

X : 0 0.71M : 50 1.3K

MOOREAFeb 25, 201346TEAM model, M(x) regarding the frequency47Models analysesModel configuration.Sinusodal input voltage : V = 500mVRon = 50 ; Roff = 5K ; D = 3nm ;Ion = -8,9uA ; Ioff = 115uA ; on = 10 ; off = 10 ;Kon = -4,68e-13 ; Koff = 1,46e-9 ; Xon = 0 ; Xoff = 3nm ;w(t0) = 0 ; Simulation on 3T = 150ns for time step = 105ps.Evolution of x and M(x) in function of frequency.Frequency200K20MEG2Gxmin000M(xmin)505050xmax1.8nm1.95nm2,1nmM(xmax)8151.2K1.7KMOOREAFeb 25, 201347TEAM model (Simmons), ion and ioff [1/2] 48Models analysesMemristor behaviors when modifying threshold currents.(I) Ioff : 115A 1mA. Model configuration.Sinusodal input voltage Vsin : 1V, F = 20MHz.Ron = 50 ; Roff = 1K ; D = 3nm ;Ion = -8,9uA ; Ioff = 115uA ; on = 10 ; off = 10 ;Kon = -4,68e-13 ; Koff = 1,46e-9 ; Xon = 0 ; Xoff = 3nm ;w(t0) = 0 ; dt = 50ps. Simulation on 3T = 150ns for time step = 150ps.

MOOREAFeb 25, 20134849Models analysesMemristor behaviors when modifying threshold currents.(II) Ion: -8.9A -50 A. Model configuration.Sinusodal input voltage Vsin : 0,5V, F = 20MHz.Ron = 50 ; Roff = 1K ; D = 3nm ;Ion = -8,9uA ; Ioff = 115uA ; on = 10 ; off = 10 ;Kon = -4,68e-13 ; Koff = 1,46e-9 ; Xon = 0 ; Xoff = 3nm ;w(t0) = 0 ; dt = 50ps. Simulation on 3T = 150ns for time step = 150ps.

TEAM model (Simmons), ion and ioff [2/2] MOOREAFeb 25, 201349TEAM model (Simmons), robustness50Models analysesTEAM model : simplified version of Simmons one.Simmons model presents huge convergence problem. Simplification through a modification of the expression of dx/dt.Even if TEAM is simpler: convergence problems (IC-CAP).Analyses performed for numerous time step when changing (V, F, dt). Convergence problems more important with TEAM window.MOOREAFeb 25, 20135051OutlineSwitching mechanims.Memristor modeling.Literature models analyses.Work in progress.Memristor models.Database for measurements performed on test structures.Discussion.

Work in progressMOOREAFeb 25, 201351Memristor models investigation [1/3]52Two models have hold our attention.(I) Enhanced version of the linear ion drift model [14]. Seems more robust than the basic model.Bipolar switching can be controlled by threshold voltages.Integrates a functional linear ion drift profile window function.(II) TEAM model [23].Model derived from a real accurate physical model.Bipolar switching can be controlled by threshold currents.Integrates a doping concentration window function.(I) and (II) : used to model the switching behavior in TiO2 structure.

Work in progress[14] Corinto, IEEE Trans. on Circuits and Systems, vol 59, no 11, 11/2012[23] Kvatinsky, Kvatinsky, CCIT (Center for Communication and information Technologies) Reports, 2011 MOOREAFeb 25, 201352Memristor models investigation [2/3]53Next steps concerning these models.(I) Enhanced version of the linear ion drift model [14]. Only few analyses have been realized.=> deeper investigation of the model.(II) TEAM model.Convergence problems => find a way to resolve them.Other ways to express the analytical relations of dx/dt and M(x) ?Are we also able to run the original model, that says Simmons one ?Work in progress[14] Corinto, IEEE Trans. on Circuits and Systems, vol 59, no 11, 11/2012[23] Kvatinsky, Kvatinsky, CCIT (Center for Communication and information Technologies) Reports, 2011 MOOREAFeb 25, 201353Memristor models investigation [3/3]54Present day memristor models are not complete.Only electrical behavior is taken into account.Models require to integrate thermal, lifetime effects.For neuromorphic applications : electrical couplings with environment.Impact of parasitive effects on memristor switching behavior ?Work in progressIn order to propose accurate models, one must consider :Theory aspect.Measurements provided by test structures : realistic data.Comparisons simulations/measurements to improve the model.MOOREAFeb 25, 201354Measurement files databaseTo compare simulations with measurements on IC-CAP.=> A Database is currently under development.

55Expected achievements with this database.Classify all the measurements files provided in the Dropbox. Call a file through a path during DUT definition in ICCAP.The file is converted in IC-CAP format.Work in progressMeasurement files treatment.Segmentation and conversion of the measurement files. Automatic classification.Permanent update of the database.MOOREAFeb 25, 201355Storing method used in database56Work in progress

MOOREAFeb 25, 201356Running Cycle_I-V_WER files [1/2]57Present Day.Segmentation of a Cycle_I-V_WER measurement file in n files.n depends on file length.nth file nth I-V cycle (work in progress).Files are converted in IC-CAP format.Work in progressTo run the measurement files.Maximum number of measurement points : 50000.Modify the file heading such that: Input parameters : Time {start ; end ; nb_pts ; time step }. Output parameters : voltage (V) and current (I).

MOOREAFeb 25, 201357Running Cycle_I-V_WER files [2/2]58Measured cycles I-V : observation under IC-CAP.Plot exhibit for numerous cycles V applied and I obtained.Work in progress

Measurement file illustrated : 2D017-1a-cycles_I-V_WER_Ag-Pt1_15-10-12MOOREAFeb 25, 201358Points to discuss about the test devices [1/2] 59Model orientation depending on developed test structures.Geometrical and technological data require.

Evolution in the technological process ?Changes in material and/or electrode types ?

First test structures. Dispersion observed.Reproducibility ? Can we return to the initial condition ?Switching behavior.Unipolar ? Bipolar ? Both.Symmetric / Asymmetric switching ?

Work in progressMOOREAFeb 25, 201359Points to discuss about the test devices [2/2] 60Cycle I-V files.Signification of V1, V2, I1, I2 ? Why most of V2 values are equal to 0 ?Measurements performed with ramp voltages.What is the maximum value reached ?

Work in progressMOOREAFeb 25, 201360