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1 Memristors with diffusive dynmics s synptic emultors for neuromorphic computing Zhongrui Wng 1, Sumil Joshi 1, Sergey E. Svel ev 2, Ho Jing 1, Rivu Midy 1, Peng Lin 1, Mio Hu 3, Ning Ge 3, John Pul Strchn 3, Zhiyong Li 3, Qing Wu 4, Mrk Brnell 4, Geng-Lin Li 5, Huolin L. Xin 6, R. Stnley Willims 3, Qingfei Xi 1, nd J. Joshu Yng 1* 1 Deprtment of Electricl nd Computer Engineering, University of Msschusetts, Amherst, MA 01003, USA 2 Deprtment of Physics, Loughorough University, Loughorough LE11 3TU, UK 3 Hewlett Pckrd Ls, Plo Alto, Cliforni 944, USA 4 Air Force Reserch L, Informtion Directorte, Rome, New York 13441, USA 5 Biology Deprtment, University of Msschusetts, Amherst, MA 01003, USA 6 Center for Functionl Nnomterils, Brookhven Ntionl Lortory, Upton, New York 11973, USA These uthors contriuted eqully to this work. * e-mil: jjyng@umss.edu NATURE MATERIALS 1

2 x 10 2 Nme Si 2p Si 2p Pos Si 2p x 10 2 Nme Pos x 10 2 Nme N 1s N 1s Pos N 1s Ag 3d x 10 3 Nme Pos. Ag 3d 5/ Ag 3d 3/ Ag 3d 3/2 Ag 3d 5/ x Nme Pos. Hf 4f 7/ Hf 4f 5/ Hf 4f Hf 4f 5/2 Hf 4f 7/ x Nme Pos x 10 2 Ag 3d Nme Pos Ag 3d 5/ Ag 3d 3/ Ag 3d 3/2 Ag 3d 5/ x Nme 80 Mg 2s Supplementry Figure S1 X-ry Photoelectron Spectroscopy (XPS) of (-d) SiOxNy:Ag (eg) HfOx:Ag, nd (h-j) MgOx:Ag films. All spectrums re clirted y lign C 1s to ev. The inding energy of Ag in ll three systems indicte metllic nture of mjority Ag prticles. Pos Mg 2s x 10 3 Ag 3d Pos. Nme Pos Ag 3d 5/ Ag 3d 3/ Mg 2s x Nme Ag 3d 3/2 Ag 3d 5/ NATURE MATERIALS

3 SUPPLEMENTARY INFORMATION nm nm 10 nm-1 10 nm-1 5 nm c 5 nm d nm 10 nm (111) (111) -1 5 nm nm (002) 10 nm-1 5 nm Supplementry Figure S2 HRTEM of Ag nnoclusters in SiOxNy:Ag film. The lttice fringes re indexed to Ag (111) plne in () () nd (c). The (d) indictes fce-centered cuic structure of the emedded Ag nnoprticle. NATURE MATERIALS 3

4 Supplementry Figure S3 The ipolr threshold switching current-voltge chrcteristics of crossr Pt/SiOxNy:Ag/Pt diffusive memristor device. 4 NATURE MATERIALS

5 SUPPLEMENTARY INFORMATION Top Electrode 100 nm Bottom Electrode 10 µm 1 µm c Supplementry Figure S4 Nnoscle crossr Pt/SiOxNy:Ag/Pt diffusive memristor nd its electricl performnce. (-) Scnning electron microgrphs of the nnoscle crossr junctions. (c) The current-voltge chrcteristics of the device. NATURE MATERIALS 5

6 V Au SiO x Ny:Ag + _ c Supplementry Figure S5 Electricl chrcteristics of Au/SiOxNy:Ag/Au lterl diffusive memristor () Schemtic of the plnr structure with two gold electrodes emedded in the dielectrics employed for in situ HRTEM. The inset shows the clustered Ag within the gp region serving s ipolr electrodes under ising. () The DC current-voltge chrcteristics showing repetle threshold switching in mient conditions. (c) A typicl plot of the timedependent relxtion of device current when 2 V excittion pulse followed y 0.2 V reding pulse is pplied in mient condition. 6 NATURE MATERIALS

7 SUPPLEMENTARY INFORMATION c d Supplementry Figure S6 The generl trend in the vrition of relxtion time s function of pulse width, pplied pulse voltge, nd the tomic concentrtion of Ag. () The relxtion time increses s function of pulse width. The pulse voltge used here ws 1.4 V. () The relxtion time increses with pulse voltge. Here the pulse width ws 4 ms. (c) The relxtion time increses with the rising tomic rtio of Ag in the co-sputtered SiOxNy:Ag (see the methods section). The pulse ws 1 V with 4 ms width. (d) Histogrm plot of the relxtion time of the diffusive memristor extrcted from 200 mesurements. The pplied pulse width nd voltge in ech independent mesurement were 4 ms nd 1.5 V, respectively. NATURE MATERIALS 7

8 1ms 1ms 1ms 160ms c Voltge,V / V th c2 1.0 c4 c6 c8 0.5 c1 c3 c5 c Time (κt) Conductnce,G/G mx 0.2 c1 c2 c3 c4 Prticle density c5 c6 c7 c Position etween leds, x/l Supplementry Figure S7 Short-term synptic plsticity with the diffusive SiOxNy:Ag memristor () Illustrtion of the voltge pulse trin for oth PPF nd PPD demonstrtions. The intervl etween djcent 3 V pulses is 1 ms (160 ms) for the PPF (PPD) cse. () The evolution of conductnce s function of the pulse cycles pplied to the device. The device is in its stedy stte efore stimultion in oth cses. The conductnce increses in the PPF cse nd decreses in the PPD cse. Plotted in the inset is the device conductnce in log scle (c) The conductnce response (lue curve) of the device due to the higher mplitude nd sprse trin of pulses (red 8 NATURE MATERIALS

9 SUPPLEMENTARY INFORMATION curve) demonstrting PPD; fcilittion does not occur since the first pulse excites enough prticles to form ridge etween the device terminls nd the system completely relxes to its low conducting stte etween sequentil pulses. Therefore, no excited prticle exists etween terminls when the next pulse rrives (see, e.g., c1-c3 or c3-c5). The suppression of conductnce y the numer of pulses still hppens due to depletion of left min cluster (compre left nd right peks in the distriutions c1, c3, c5, c7), therefore, less nd less prticles re excited to uild conducting ridge etween the terminls (compre c2, c4, c6, c8). Detils of simultions nd prmeters used re descried in the methods section nd in the cption of Fig. 4 (min text). Note, the depletion sturtion cn occur due to, e.g., (i) inter-prticle repulsion discussed in Ref. 1, nd (ii) diffusion flux ginst density grdient which is fully tken into ccount in the model descried here. NATURE MATERIALS 9

10 Supplementry Figure S8 Anlog switching ehviour of the Pt/TOx/T/Pt drift memristors used for the spike-rte-dependent plsticity demonstrtion of the Figure 6 nd 6d () Typicl DC current-voltge chrcteristics of the device. The forming voltge ws ~ 6 V () Pulse sed switching response. Plot shows the red current following ech pulse in susequent progrmming opertions on the device. The progrmming pulse width ws 0 ns, the set voltge ws 0.7 V, reset voltge ws -1 V, nd the red voltge ws 0.1 V. 10 NATURE MATERIALS

11 SUPPLEMENTARY INFORMATION Post-Spike Pre-Spike Low Resistnce Post-Spike Pre-Spike High Resistnce Time Supplementry Figure S9 Illustrtion of sttes evolution in STDP protocol () An exmple of the evolution of sttes of oth the diffusive nd drift memristors during the depression process. The post-spike turns the diffusive memristor ON. The conductnce of the diffusive memristor decys to certin level fter the post-spike. The high voltge pek of the pre-spike decreses the conductnce of the drift memristor. The conductnce of the diffusive memristor decys nd it turns OFF fter the pre-spike. () An exmple of the evolution of sttes in the potentition process. The pre-spike turns the diffusive memristor ON. The conductnce of the diffusive memristor decys to certin level fter the pre-spike. The high pek of the post-spike increses the conductnce of the drift memristor. The diffusive memristor conductnce decys nd it turns OFF fter the post-spike. NATURE MATERIALS 11

12 c Supplementry Figure S10 STDP with Pt/HfOx/TiN drift memristor () Typicl I-V Pt/HfOx/TiN drift memristors used for STDP demonstrtion with forming voltge of ~ 4 V. () An exmple of the ctul pre- nd post-synptic voltge spikes pplied cross the device for STDP demonstrtion. The pre-spike consisted of 50 µs/4 V pulse for progrmming the drift memristor followed y 10 ms/2 V pulse for progrmming the diffusive memristor. The post-spike hd 50 µs/3 V pulse followed y 10 ms/2 V pulse. We performed five mesurements t ech time difference t nd n verge ws clculted to plot the STDP chrcteristics. In order to normlize the STDP plot to 100%, the weight chnge ws tken to e equl to the rtio of the chnge in conductnce due to progrmming nd the high conductnce vlue. (c) Plot of the conductnce (weight) chnge of the drift memristor with chnge in Δt showing the spike-timing-dependent plsticity of the electronic synpse. This response is chrcteristic of the timing-dependent response of iologicl synpses. 12 NATURE MATERIALS

13 SUPPLEMENTARY INFORMATION Reference 1 Yi, W. et l. Quntized conductnce coincides with stte instility nd excess noise in tntlum oxide memristors. Nt. Commun. 7, 11142, (2016). NATURE MATERIALS 13