Embedded metallic nanoparticles facilitate metastability of switchable metallic domains in Mott threshold switches

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Nature Communications volume 13, Article number: 4609 (2022) Cite this article

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Mott threshold switching, which is observed in quantum materials featuring an electrically fired insulator-to-metal transition, calls for delicate control of the percolative dynamics of electrically switchable domains on a nanoscale. Here, we demonstrate that embedded metallic nanoparticles (NP) dramatically promote metastability of switchable metallic domains in single-crystal-like VO2 Mott switches. Using a model system of Pt-NP-VO2 single-crystal-like films, interestingly, the embedded Pt NPs provide 33.3 times longer ‘memory’ of previous threshold metallic conduction by serving as pre-formed ‘stepping-stones’ in the switchable VO2 matrix by consecutive electical pulse measurement; persistent memory of previous firing during the application of sub-threshold pulses was achieved on a six orders of magnitude longer timescale than the single-pulse recovery time of the insulating resistance in Pt-NP-VO2 Mott switches. This discovery offers a fundamental strategy to exploit the geometric evolution of switchable domains in electrically fired transition and potential applications for non-Boolean computing using quantum materials.

Quantum materials featuring an abrupt metal-insulator transition have fascinated researchers for their variety of potential applications in future electronics1,2,3,4,5,6,7,8,9,10. Due to the extreme sensitivity of the electronic phase transition between competing phases, a subtle perturbation by external stimuli can abruptly transform an existing phase into a different electronic phase, leading to steep modulation of the electrical properties7,8,9,10,11,12. A characteristic phenomenon during the first order metal-insulator transition is the appearance of phase separation with metallic and insulating domains with inhomogeneous distributions down to a few nanometers11,13,14,15,16,17. The existence of phase separation implies that the resistance modulation occurs through a series of percolation transforming parts of the system from one phase to the other2,11,13,14,15,16,17,18,19. This percolative nature allows for an inhomogeneous transitional state where both metallic and insulating phases coexist; the dynamics of percolative domains in the intermediate state determines the macroscopic properties related to phase transition in quantum materials2,11,13,14,15,16,17,18,19.

Vanadium dioxide (VO2) undergoes a reversible transition between a monoclinic insulating phase and a rutile metallic phase near room temperature13,20,21. This thermally induced transition results in a giant modulation of electrical resistivity of up to five orders of magnitude, accompanied by changes in crystal symmetry and optical properties7,9,13,14,15,20,22. Uniformly distributed thermal energy over the whole VO2 results in a spatially random generation of nanoscale metallic puddles; these metallic puddles nucleate and then grow as metallic domains in the insulating matrix with increasing temperature, and eventually connect the entire area of VO2 as a result of gradual percolation7,9,13,14,15,19,20,22. The metallic domains are destabilized with decreasing temperature in a reversible manner.

In addition to temperature as an external stimulus, the insulator-to-metal transition (IMT) can be electrically stimulated on a subnanosecond time scale by applying an external voltage on two-terminal VO2 devices if a threshold voltage (Vth) is exceeded2,7,14,16,17,18,23,24,25,26. A reverse metal-to-insulator transition (MIT) can promptly occur once the electrical stimulus is removed. These abrupt transitions by electrical stimuli have made VO2 a candidate for threshold switches in potential applications of low-voltage logic devices for energy-efficient switches27 and in artificial spiking neurons and synapses for non-Boolean computing2,4,6 to resolve the bottleneck in the state-of-the-art electronic devices.

This electrically triggered IMT induces anisotropic growth of metallic puddles in the domain evolution and a subsequent increase of percolated metallic domains along the direction of the electric field between two electrodes2,14,16,17,25,26. Geometric evolution of the switchable (metallic or insulating) domains significantly influences the macroscopic physical properties of VO2 (e.g., degree of resistivity modulation, steepness of phase transition); the performance of VO2-based threshold switches could be tuned by effectively bridging two electrodes by evolving metallic domains in the insulating matrix (left in Fig. 1a)2,14,16,17,25,26. Permanently embedded metal in the switchable VO2 matrix28,29 may serve as ‘stepping-stones’ to assist the bridging and stabilization of metallic domains during electrically triggered IMT switching dynamics (right in Fig. 1a). However, it is challenging to incorporate metallic nanoparticles (NPs) in single-crystalline VO2 without deteriorating the characteristics of IMT due to crystallographic mismatch between the metal and VO2.

a Schematics of epitaxial VO2 films on (001)-TiO2 substrates and Pt NP-decorated (001)-TiO2 substrates. VO2 epitaxial films are selectively nucleated on TiO2 single-crystal substrates and epitaxially and laterally overgrown onto Pt NPs, which act as "stepping stones" for electrical conduction by insulator-to-metal transition. b Reciprocal space mapping around the (112) reflection of (001) TiO2 substrate. Coherently tensile-strained VO2 epitaxial films were preserved on both TiO2 substrates (tPt = 0 s) and Pt NP-TiO2 substrates (tPt = 5 s). c Cross-sectional HAADF-STEM image and elemental EDS mapping of VO2 epitaxial films on Pt NP-TiO2 substrates (tPt = 5 s). d Magnified HAADF-STEM image of high-quality epitaxial VO2 films on Pt NP-TiO2 substrates along the [010] zone axis. e Temperature-dependent sheet resistance of VO2 epitaxial films without Pt NP incorporation (tPt = 0 s, black dotted line) and with Pt NP incorporation (tPt = 1–5 s, a series of red solid lines). All VO2 films consistently show a steep transition regardless of Pt NP coverage. All Pt-NP-embedded VO2 films consistently show a single-crystal-like steep insulator-to-metal transition at identical temperature with hysteresis, which electrically confirms undamaged crystal-quality of fully epitaxial VO2 films with randomly oriented metallic Pt NPs.

Here, we demonstrate that embedded metallic NPs promote electric-field-induced metastability of switchable metallic domains in epitaxial VO2 thin films (Fig. 1a). After the decoration of uniformly dispersed Pt NPs with different coverage on TiO2 substrates, the growth of VO2 films allows the selective nucleation on TiO2 substrates and subsequent overgrowth on Pt NPs; all Pt-NP-embedded VO2 epitaxial films uniquely exhibit a single-crystal-like steep insulator-to-metal transition near room-temperature, which benefits from undamaged crystal quality of fully epitaxial VO2 films with metallic Pt NPs. Using this excellent model system to study the influence of a permanent metallic regime on the switchable (metallic or insulating) domains in the VO2 matrix, embedded Pt NPs make a significant contribution to reducing the power consumption by decreasing Vth in two-terminal threshold devices. More importantly, embedded Pt NPs are likely to provide 33.3 times longer ‘memory’ of previous super-threshold firing by serving as pre-formed ‘stepping-stones’ between triggered metal domains in the VO2 matrix; memory of previous threshold firing is retained for longer than a six orders of magnitude timescale (τ50% = 437.88 ms) after the insulating resistance has recovered (toff = 190 ns) in Pt-NP-embedded VO2 epitaxial films. These results emphasize the importance of geometric evolution of the switchable (metallic or insulating) domains in the metal-insulator transition to control macroscopic physical properties by switching dynamics. Moreover, this strategy can be exploited in potential applications of versatile devices for energy-efficient switches (e.g., solid-state frequency discriminator)2,5 and for non-Boolean computing (e.g., artificial spiking neurons and synapses using time-dependent plasticity)4,5,6.

Without Pt nanoparticle (NP) incorporation (i.e., tPt = 0 s), 10 nm-thick (001)R-oriented VO2 epitaxial films (in rutile notation) were directly grown on (001) TiO2 substrates at 400 °C (left in Fig. 1a) by pulsed laser deposition (PLD). X-ray diffraction (XRD) results at 25 °C showed a sharp (002)R rutile VO2 peak at ~ 2θ = 65.9° without other peaks related to vanadium oxides that had valence states other than +4 (See Supplementary Fig. 1). Moreover, reciprocal space mapping (RSM) around the (112) reflection of the (001) TiO2 substrate clearly showed identical in-plane reciprocal space unit of TiO2 substrates and VO2 films (left in Fig. 1b)22,30,31,32,33; these results represent the formation of coherently tensile-strained VO2 films on TiO2 substrates along the in-plane direction with high crystal quality (See Supplementary Fig. 2)22,30,31,32,33.

To embed metallic NPs into epitaxial VO2 films without damaging the crystal quality of VO2 films, different density of Pt NPs was provided using sputtering on TiO2 substrates by controlling the Pt deposition time (tPt ≤ 5 s)9,31,34. Since Pt deposition ceased before island coalescence, a cross-sectional high-angle annular dark field (HAADF) image confirms that several nanometers of Pt islands are uniformly dispersed on the TiO2 substrates and are disconnected with the adjacent Pt islands (Fig. 1c)9,31,34. Then, 10-nm-thick VO2 thin films were grown at 400 °C by PLD on Pt NP-decorated (001)R-TiO2 substrates (denoted as Pt NP-TiO2 hereafter) with different coverage of Pt NPs (tPt ≤ 5 s) (right in Fig. 1a).

Interestingly, high crystal quality of VO2 epitaxial films was preserved on Pt NP-TiO2 substrates regardless of the Pt NP decoration with different coverage. A series of RSM data consistently showed identical in-plane reciprocal space unit of strong (112) VO2 reflection with TiO2 substrates in all VO2 films on Pt NP-TiO2 (tPt = 0, 1, 3, 5 s) (Fig. 1b, See Supplementary Fig. 3); these results implicate the stabilization of coherently strained epitaxial VO2 films even on Pt NP-TiO2 substrates (right in Fig. 1b)22,30,31,32,33. The formation of high-quality epitaxial VO2 films on Pt NP-TiO2 could be confirmed by cross-sectional scanning transmission electron microscopy (STEM) analysis with energy dispersive spectroscopy (EDS) mapping of VO2/Pt-NP-TiO2 (tPt = 5 s) samples (Fig. 1c, d). The bright contrast in HAADF-STEM and the yellow regions in the element-resolved EDS mapping confirm that randomly oriented Pt NPs are uniformly dispersed on the TiO2 substrates (Fig. 1c). From magnified HAADF-STEM image at the atomic scale along the [010] zone axis (Fig. 1d), the VO2 thin film is epitaxially grown even on the randomly oriented Pt NPs, as well as on TiO2 substrates between separated Pt NPs; the in-plane lattice parameter of VO2 epitaxial film perfectly matched that of TiO2 single-crystal substrates with coherent interfaces, which is consistent with the RSM (Fig. 1b), selective-area diffraction pattern (See Supplementary Fig. 4) and geometric phase analysis for strain (See Supplementary Fig. 5).

To confirm the intact quality of Pt-NP-embedded VO2 epitaxial films, temperature-dependent sheet resistance was measured in order to characterize the metal-insulator transition characteristics for VO2 epitaxial films with different Pt coverage (0 ≤ tPt ≤ 5 s) (Fig. 1e). Due to the increased volume fraction of permanent metallic Pt NPs embedded into the insulating VO2 phase, the sheet resistance of the insulating phase (T < TMI) decreased with increasing Pt NP coverage from tPt = 0 to tPt = 5 s. However, regardless of the Pt NP coverage, it should be emphasized that all Pt-NP-embedded VO2 films consistently show a steep insulator-to-metal (and metal-to-insulator) transition at identical temperature (TIM ~ 20 °C, TMI ~ 14 °C) with hysteresis; this steep transition would be only observed in single-crystal-like VO2 films2,18,30,31, which confirms on undamaged crystal quality of fully epitaxial VO2 films with Pt metallic NPs.

The epitaxy of VO2 films on randomly oriented Pt NPs is remarkable because the absence of lattice matching fundamentally limits epitaxial growth of functional layers on underlying layers without crystallographic coordination. Our observation of (001)R-VO2 epitaxial films both on (001) TiO2 substrates and on Pt NPs indicates that VO2 crystals initially prefer to nucleate on the TiO2 single-crystal substrates, rather than randomly oriented Pt NPs, and then lateral VO2 growth was seeded by epitaxial deposits initially formed on exposed regions of the TiO2 substrates35. Thus, this sequential VO2 growth (i.e., selective nucleation on single-crystal substrates + epitaxial lateral overgrowth onto metallic NPs, right in Fig. 1a, See Supplementary Fig. 6) enables transfer of crystal information from TiO2 substrates even onto metallic NPs. Due to the selective nucleation and subsequent overgrowth of VO2 films, the roughened surface by Pt NPs before the VO2 growth (rRMS = 0.225 nm) was flattened after the VO2 growth (rRMS = 0.124 nm) (See Supplementary Fig. 7).

For heterogeneous nucleation on the substrate during the film growth, the heterogeneous nucleation rate (Nhet) strongly depends on the activation barrier (ΔG*) for the formation of crystalline nuclei (i.e., \({N}_{{het}}\propto {\exp }(-\frac{{\triangle G}^{*}}{{kT}})\)). Depending on films and underlying substrates, the activation barriers are determined based on the following expression36.

where ΔGv, γ, and S(θ) are the chemical free energy change for the formation of solid VO2 nuclei, interfacial free energies, and a geometrical factor for heterogeneous nucleation, respectively. By comparing the nucleation of VO2 films on single-crystal TiO2 with that on randomly oriented Pt, ΔG* (VO2 on TiO2) would be substantially lower than ΔG* (VO2 on Pt) due to lower γ by the coherent interface between VO2 and TiO2. Moreover, the sticking coefficient of VO2 on single-crystal TiO2 is much larger than that on Pt (i.e. VO2 nuclei is more easily formed on the TiO2 surface than on the Pt surface)37,38. Preferential nucleation of VO2 films is guided by TiO2 single-crystal substrates at the initial growth stage, and then permits subsequent epitaxial lateral overgrowth and coalescence of epitaxial VO2 films onto Pt NPs by faster crystal growth oriented in the <110> and <100> direction (i.e. lateral direction of the VO2 film) due to a lower surface energy than that of the <001> direction35,39.

Our single-crystal-like VO2 films with embedded Pt NPs provide an excellent model system to study the influence of permanent metallic domains (i.e., Pt) on the percolation of switchable (metallic or insulating) domains (VO2); this unconventional geometric evolution would strongly influence the performance of VO2-based threshold switches utilizing an electric-field-induced steep transition. For this purpose, two-terminal devices were fabricated with an electrode separation of 5 \(\mu\)m and an electrode width of 100 \(\mu\)m on Pt-NP-embedded epitaxial VO2 films, as shown in optical microscope images (Fig. 2a); narrow electrode separation (~5 \(\mu\)m) allows the application of a sufficient electric field (~1.7 MV/m) to trigger electrically induced threshold ΙΜΤ switching using several volts23,40. As the applied voltage was increased, a sudden increase in current was observed in all two-terminal devices with Pt-NP-embedded epitaxial VO2 films (Fig. 2b). This switching is volatile: as the voltage is reduced, the current decreases sharply; all two-terminal devices showed abrupt voltage-triggered threshold ΙΜΤ switching. The threshold voltage (Vth) with normal distribution is strongly modulated by coverage of Pt NPs embedded in VO2 films (Vth = 6.54 V for tPt = 0 s → \({V}_{{th}}\) = 3.80 V for tPt = 5 s). (Fig. 2b, See Supplementary Fig. 8).

a Schematic representation of the voltage-triggered insulator-to-metal transition (IMT) measurement setup and optical microscope image of VO2 Mott switch with 5 \(\mu\)m electrode separation and 100 \(\mu\)m electrode width. The performance of VO2-based threshold switches was measured with either a continuous voltage sweep or an ultrafast voltage pulse. b Continuous voltage sweep of all two-terminal devices with Pt-NP-embedded epitaxial VO2 films. c The power to turn on a threshold device with tPt= 0 s and 5 s. Solid lines are the linear best fits to the data, which were extracted from Supplementary Fig. 6. d The transient current response to three pulses with different amplitudes (7.3 V, 7.9 V, and 8.1 V) in VO2 threshold devices without Pt NP coverage (tPt = 0 s). e The transient current response to three pulses with different amplitudes (6.8 V, 7.0 V, and 7.3 V) in VO2 threshold devices with Pt NP coverage (tPt = 5 s). The duration of the pulse is set to 100 \(\mu\)s. f The probability of firing the IMT (PFiring) as a function of the pulse amplitude (Vpulse) for each tPt. Vth,pulse decreased with increasing tPt. The error bars were calculated using the standard deviation of the binomial distribution. g Transient electrical resistance vs. time behavior of VO2 threshold devices with Pt NP coverage (tPt = 5 s) immediately after the 100 \(\mu\)s voltage pulse is off at T = 12 °C.

The reduced Vth for Pt-NP-embedded VO2 films is advantageous for reducing the switching power of voltage-triggered IMT. The power to turn on a threshold device (PON) was calculated according to the following relationship23.

where Gtherm, ROFF, and Vth are the thermal conductance, the electrical resistance below TIMT, and the voltage at which the device turns on, respectively. To investigate the influence of embedded Pt NPs on the VO2 threshold switching power, two-terminal IV characteristics were measured as a function of temperature below TIMT (See Supplementary Fig. 9); Vth also linearly decreased with temperature. The linear ΔT dependence of PON is characteristic of Joule-heating induced IMT switching. Owing to the more reduced Vth with greater Pt NP coverage, devices with tPt = 5 s (e.g., PON = 3.103 mW at 4 °C) show much lower power consumption that those with tPt = 0 s (e.g., PON = 6.195 mW at 4 °C) (Fig. 2c).

Therefore, permanent Pt NPs embedded in the VO2 matrix make a significant contribution to reducing the power consumption to induce an electrical conduction pathway between two electrodes in threshold devices. In particular, electric-field-induced Joule heating between two electrodes leads to an abrupt redistribution of local temperature3,14,26, which in turn leads to the localized connection of metallic domains along the direction of the electric field (right in Fig. 1a). From a microscopic viewpoint, the decrease of Vth indicates that permanent Pt NPs lower the energy consumption to connect percolated metallic domains by electric-field-induced nucleation and anisotropic growth of switchable metallic domains in VO23,5,14,25,26. If permanent metallic Pt NPs are randomly distributed in the VO2 matrix, the threshold electric field to nucleate metallic domains in VO2 and bridge the electrodes is reduced by shortening the connecting current path: embedded Pt NPs act as stepping-stones for current flow between the electrodes. Moreover, the presence of permanent metallic inclusions creates an inhomogeneous field distribution in the VO2 matrix41; The electric field in the insulating VO2 matrix between Pt metallic NPs is greatly enhanced due to a field-focusing effect; this enhancement locally triggers the IMT at reduced electric field and power consumption.

Facilitated threshold switching by embedded Pt NPs in the epitaxial VO2 matrix significantly affects the switching dynamics of the phase transition subjected to ultrafast voltage pulse (Fig. 2d, e, See Supplementary Fig. 10). In particular, exciting the system with a voltage pulse, not a continuous voltage sweep, and monitoring the recovery process provides a probing technique, which enables to capture the dynamic evolution of the switchable domain as a function of time2,3,5,19,42. The amplitude of input voltage pulses was modulated from 6.0 V to 9.0 V with 100 μs pulse duration at 12 °C to switch the insulating states to metallic states in a VO2 Mott switch with different Pt coverage (tPt = 0–5 s) (Fig. 2d, e, See Supplementary Fig. 10).

The characteristics of pulse-triggered threshold switching were clearly demonstrated by an abrupt current response as a function of the input voltage-pulse amplitude near the threshold amplitude (Vth,pulse). The gray and black plots in Fig. 2d show the transient current response to three pulses of different amplitude (7.3 V, 7.9 V, and 8.1 V) in VO2 threshold devices without Pt NP coverage (tPt = 0 s). The distinct difference between them represents the steep threshold characteristics of an electrically triggered IMT by 100 μs pulse: electrical pulse stimuli are insufficient to induce IMT threshold switching if Vpulse < Vth,pulse (Vpulse ~ 7.9 V for VO2 (tPt = 0 s)), while Vpulse > Vth,pulse (i.e., Vpulse ~ 8.1 V for VO2 (tPt = 0 s) in Fig. 2d) yields an abrupt increase of current (ION / IOFF > 103), which was limited by an external compliance current. We note that Vth,pulse and IOFF (i.e., related to the resistance of insulating phase) remained unchanged after more than 100 repetitive firing events, ruling out that device degradation or defect creation is responsible for the effect16.

Vth,pulse for a voltage-pulse-triggered IMT was modulated by Pt NP-embedded VO2 threshold devices. Despite the universal feature on current amplification at Vpulse > Vth,pulse in all Pt NP-embedded VO2 devices, Vth,pulse for a voltage-pulse-triggered IMT was systematically decreased with increasing Pt NP coverage down to 15% (i.e., Vth,pulse = 8.0 V, 7.5 V, 7.1 V, 6.8 V for tPt = 0 s, 1 s, 3 s, 5 s, respectively) (see Fig. 2d, e, See Supplementary Fig. 10). These distinct characteristics in Vth,pulse are statistically quantified in Fig. 2f, where the probability of firing the IMT (PIMT) as a function of the pulse amplitude (Vpulse) shows a step-like behavior around Vth,pulse: PIMT = 0, where Vpulse < Vth,pulse and PIMT = 1, where Vpulse > Vth,pulse. Vth,pulse for an abrupt threshold conduction decreases with Pt NP coverage (tPt = 0 → 5 s); embedded Pt NPs accelerate percolation and bridging of metallic domains by voltage pulse in an ultrafast time regime.

To evaluate how fast this volatile metallic state returns to the insulating state after the voltage pulse ceases, the resistance was monitored immediately after the pulse application of an 8.0 V amplitude and 100 μs duration in the VO2 Mott switches as a function of time (Fig. 2g (for tPt = 5 s), See Supplementary Fig. 11 (for tPt = 0 s))2. The threshold devices show a transient increase of resistance. Regardless of the existence of Pt NP, resistance remains close to metallic states for ~190 ns (toff; black arrows both in Fig. 2g and in See Supplementary Fig. 11) before rising abruptly. Since toff can be regarded as the characteristic time for the reverse MIT switching, this toff provides timescale to lose percolation of the Joule-heating-induced metallic pathway after the removal of the external voltage pulse2,13,14.

Due to the percolative nature of IMT and MIT during the application and removal of the input voltage pulse, respectively, the current output shows a distinct response by consecutive pump-probe pulses (Fig. 3a)2,5. In particular, even if the second probe pulse is applied below Vth,pulse, metallic output current can be triggered (i.e., sub-threshold firing), as long as certain delay time (\(\tau\)) for the relaxation is short enough to ‘memorize’ the previous firing event by the preceding super-threshold pump pulse (Fig. 3). Since ‘sub-threshold firing’ is governed by the characteristic time of phase relaxation, a pump-probe procedure by electric pulses was utilized to investigate how this percolative systems relaxes. For example, a ‘super-threshold’ pump pulse with amplitude Vpump = 1.25 Vth,pulse and duration of 100 μs was firstly applied to excite the VO2 films, and metallization was thereby triggered. Then, after a different delay time (τ = 500 μs and 1000 μs) for the relaxation, a second voltage pulse (probe) was sent with sub-threshold amplitude (Vprobe < Vth,pulse) and 100 μs duration (Fig. 3b, c).

a Conceptual illustration of percolative (sub-)threshold firing of Pt-NP-embedded VO2 Mott switches by consecutive electrical pulses. Even if the second probe pulse is applied below Vth,pulse, the metallic domain (red) can be connected by IMT switching from insulating domains (blue) assisted by the permanent metallic Pt ‘stepping stone’ (coral) due to the percolative nature of the IMT, as long as a certain delay time (τ) for the relaxation is short enough to ‘memorize’ the previous firing event by the super-threshold pump pulse. b, c Transient current output by two consecutive voltage pulses with different delay time measured by a pump-probe procedure at T = 12 °C: a super-threshold pulse is firstly applied to trigger the insulator-to-metal transition, followed by a sub-threshold probe pulse, after a delay time τ. (b τ1 = 500 \(\mu\)s and c τ2 = 1000 \(\mu\)s between the two consecutive pulses). d Probability that the probe pulse will trigger the insulator-to-metal transition (PFiring) as a function of τ at T = 12 °C depending on Pt NP coverage. PFiring is plotted for Vprobe = 0.5 Vth,pulse with different Pt NP coverages: tPt = 0 s, 1 s, 3 s, and 5 s. This probability was obtained after averaging 100 pump–probe measurements at each τ. e Delay time at which the sub-threshold firing probability is 50% (τ50%) plotted against Vprobe/Vth,pulse at 12 °C. τ50% was calculated using the fitting curves shown in d. The error bars in d and e were calculated using the standard deviation of the binomial distribution.

It is possible to re-trigger the IMT by using low sub-threshold voltage pulse (Vprobe = 0.5 Vth,pulse) in a much longer time interval between pulses (τ1 = 500 μs) in Pt-NP-embedded VO2 devices (Fig. 3b). With a single pulse, this subthreshold pulse should not trigger the IMT; it should be emphasized that this Vprobe is much lower than the Vth,pulse, and is in contrast to the non-firing behavior under single pulse applications. This ‘memory’ of the previous firing was lost at a pump-probe time interval of τ2 = 1000 μs (> τ1) (Fig. 3c). This result indicates that the device maintains a certain ‘memory’ of the previous firing event and thus facilitates the firing again with sub-threshold pulses2,5.

Interestingly, the delay time (τ) between pump and probe pulses is 500 \(\mu\)s, which is more than three orders of magnitude larger than the electrically measured MIT recovery time (toff ~ 190 ns). Metal-to-insulator recovery after removal of the voltage pulse corresponds to the rupture or depercolation process of already formed metallic filaments2,5,13,14,24. The evolution of subthreshold firing at τ ≫ toff indicates that memory of previous super-threshold switching is retained long after the insulating resistance has recovered. From a microscopic viewpoint, metallic domain puddles are likely to exist for a much longer time in the localized area after the rupture and depercolation process of the pre-formed metallic filament for electric conduction by the preceding threshold Vpump.

To investigate the influence of Pt NP coverage on this characteristic time (τ) of ‘memory’ of the metallic domain, we carried out a pump-probe experiment of VO2 threshold devices with different Pt NP coverage (tPt = 0–5 s) by changing the pulse separation time (τ) (Fig. 3d, e). The probability for the second probe pulse to trigger the metallic conduction is shown in Supplementary Fig. 12 as a function of τ for different amplitudes of Vprobe. Since ‘memory’ of metallic triggering is likely to be lost as the pulse separation time (τ) increases, the probability consistently decreases with τ regardless of the Pt coverage (Fig. 3d). By defining τ50% as the delay time for which the firing probability declines to 50%, τ50% increases with amplitude of Vprobe (Fig. 3e) and temperature (See Supplementary Fig. 13); the increase of the second pulse amplitude substantially enhances the success probability for subthreshold firing (Fig. 3e). More importantly, as Pt NP coverage increases (tPt = 0 s → tPt = 5 s), τ50% increases by up to 33.3 times longer at the same Vprobe (e.g., τ50% = 13.15 ms (for tPt = 0 s) → τ50% = 437.88 ms (for tPt = 5 s) at Vprobe = 0.8 Vth,pulse) (Fig. 3e). It should be emphasized that the memory of previous threshold firing is retained for longer than a six orders of magnitude timescale (τ50% = 437.88 ms) after the insulating resistance has recovered (toff = 190 ns) in Pt-NP-embedded VO2 epitaxial films.

Therefore, embedded Pt NPs in the VO2 matrix are likely to enhance the ‘memory’ of previous firing as pre-formed ‘stepping-stones’ between fired metal domains in VO2; these permanent metallic ‘stepping-stones’ significantly facilitate sub-threshold firing in the consecutive pulses. Moreover, metallic domain puddles are ruptured (or disconnected) after the removal of the preceding ‘super-threshold’ pulse; these metastable metallic puddles are likely to remain trapped longer in Pt NP-embedded VO2 films than in pure VO2 films. Thus, these persistent and long-lived domains after the preceding threshold switching act as nuclei that facilitate triggering of the subsequent IMT with a subthreshold voltage pulse; persistent metallic domains enhanced by permanent Pt NPs are indeed responsible for the longest memory effect in the Pt NP-embedded VO2 films (tPt = 5 s).

The microscopic origin of persistent metallic domains in the Pt NP-embedded VO2 films is attributed into electron doping by the charge transfer from Pt. The lowered work function of Pt NPs (~4.6 eV)29 than VO2 (~5.0 eV) leads to charge carrier injection from small Pt NPs into VO2 matrix by Fermi level alignment between Pt NP and VO2, forming an electron rich region in the VO2 matrix near the Pt NP contact interface; this ‘local’ electron doping near Pt NPs may result in the local stabilization of ‘persistent metallic domain’; these persistent and long-lived ‘metastable’ metallic domains after the super-threshold switching act as nuclei that lower the activation barrier and facilitate re-triggering of the subsequent IMT with a subthreshold voltage pulse.

The dependence of sub-threshold firing probability on τ could be exploited as a high-pass filter (i.e., frequency discriminator)2,5. The super-threshold pulse is followed by a series of sub-threshold pulses separated by τ, which determines the frequency (f) of electrical stimuli (Fig. 4a–c). Repetitive subthreshold pulses with different f were applied after the super-threshold pulse through two-terminal devices with Pt NP-embedded VO2 films. Each sub-threshold pulse refreshes the memory of the devices, allowing for continuous subthreshold firing and signal transmission at a high pulse frequency (e.g., τ = 500 μs (f = 2 kHz), Vprobe = 0.5 Vth,pulse for VO2 with tPt = 5 s in Fig. 4a) at f higher than the cut-off frequency (fCO); subthreshold firing ceases at f < fCO (e.g., τ = 1000 μs (f = 1 kHz), Vprobe = 0.5 Vth,pulse for VO2 with tPt = 5 s in Fig. 4b) or at lower Vprobe (e.g., τ = 500 μs (f = 2 kHz), Vprobe = 0.35 Vth,pulse for VO2 with tPt = 5 s in Fig. 4c). Consequently, clear and sharp (almost 35 dB) high-pass filter characteristics were observed with Vprobe-dependent fCO in all devices (Fig. 4d, e); these characteristics show the possibility of tuning the fCO for signal transmission by adjusting the amplitude of the incoming sub-threshold signal: a lower amplitude of repetitive Vprobe leads to a higher fCO.

a–c Transient current output (top panels) by multiple consecutive voltage pulses with different pulse separation (or frequency, bottom panels) at T = 12 °C: The preceding super-threshold pulse is followed by a series of subthreshold voltage pulses separated by 500 \(\mu\)s (a, c) or 1000 \(\mu\)s. b with probe voltage amplitude of Vprobe = 0.5Vth,pulse (a, b) or Vprobe = 0.35Vth,pulse c. Note that when the pulse separation is 500 \(\mu\)s at Vprobe = 0.5Vth,pulse, each voltage pulse refreshes the memory of the device, allowing for repeated subthreshold firing. d, e Attenuation of a pulsed signal through a device as a function of the signal frequency. Several signal amplitudes are shown with d, tPt = 0 s and e, tPt = 5 s. f Cut-off frequency (fCO) of Pt-NP-embedded VO2 Mott switches plotted against each Pt NP coverage (tPt) with several signal attenuation levels.

Notably, Pt NP-embedded VO2 devices (tPt = 5 s) enable a wider range of fCO tuning (fCO = 2 Hz at Vprobe = 0.8 Vth,pulse to fCO = 670 kHz at Vprobe = 0.05 Vth,pulse) compared to that from pure VO2 devices (tPt = 0 s) (fCO = 67 Hz at Vprobe = 0.8 Vth,pulse to fCO = 67 kHz at Vprobe = 0.35 Vth,pulse) (Fig. 4f). The enhanced τ50% of long-lived metallic domains in Pt-embedded VO2 films leads to subthreshold firing at a lower frequency (higher τ) of repetitive electrical pulse signal; embedded Pt NPs give rise to enhanced connectivity of repetitive stimuli. Moreover, reduced switching power in Pt-embedded VO2 films contributes to subthreshold firing at a lower Vprobe amplitude (e.g. Vprobe = 0.2 Vth,pulse was not subthreshold fired at the Pt-embedded VO2 with tPt = 0 s but fired at the Pt-embedded VO2 with tPt = 5 s); embedded permanent metallic NPs bring stable percolation of switchable metallic domains at lower stimuli; a delayed memory effect of switchable metallic domain in VO2 films by Pt metallic ‘stepping-stones’ leads to f-tunable subthreshold firing in a wider f range.

In summary, voltage-triggered metastability of switchable metallic domains was enhanced by embedded metallic NPs that serve as ‘stepping-stones’ in a switchable epitaxial VO2 matrix. The ability to selectively nucleate epitaxial VO2 films on TiO2 substrates, rather than uniformly dispersed Pt NPs, enables a single-crystal-like steep insulator-to-metal transition near room-temperature with different coverage of permanent metallic NPs in the switchable matrix. Using this distinct model system, we systematically investigated the effect of permanent metallic domains on the dynamics of switchable (metallic or insulating) domains in VO2 matrix. In particular, embedded Pt NPs make a significant contribution to better inscribed ‘memory’ of previous firing by serving as pre-formed stepping-stones between triggered metal domains in the VO2 matrix. In consecutive input pulses, remarkably, memory of previous super-threshold firing is kept for longer than a six orders of magnitude timescale (τ50% = 437.88 ms) even after the insulating resistance recovered (toff = 190 ns) in Pt-NP-embedded VO2 epitaxial films.

These characteristics could be used to implement functionalities in oxide electronics. Our results demonstrate that a high-pass filter (i.e., frequency discriminator) can be simply tuned by modified intrinsic dynamics of a percolative phase transition, which is assisted by embedded Pt NP coverage in the VO2 matrix. Our results clarify the influence of permanent metallic domains on geometric evolution of switchable (metallic or insulating) domains in a metal-insulator transition. From a practical viewpoint, this strategy to exploit the enhanced ‘memory’ of previous firing by uniformly distributed metallic stepping-stones could open up potential applications of versatile devices for energy-efficient switches2,5 and for non-Boolean computing4,5,6.

Different density of nano-sized Pt islands was formed by controlling the Pt deposition time (0 s ≤ tPt ≤ 5 s) on (001) TiO2 single crystals at room temperature by sputtering. Since Pt deposition ceased before island coalescence, cross-sectional high-angle annular dark field (HAADF) in scanning transmission electron microscopy (STEM) confirms that several nanometer Pt islands are uniformly dispersed on the TiO2 substrates and are disconnected from the adjacent Pt nanoparticles (NP). Then, 10-nm-thick VO2 thin films were grown at 400 °C on Pt NP-decorated (001)R-TiO2 substrates with different coverage of Pt NPs (0 s ≤ tPt ≤ 5 s) by pulsed laser deposition with the base pressure of the growth chamber set at ~10−6 Torr. A KrF excimer laser (λ = 248 nm) was focused onto a stoichiometric V2O5 rotating target at fluence ~1.5 J cm−2 pulse−1 and a repetition rate of 2 Hz. The VO2 films were grown in oxygen ambient of 10 mTorr and at a growth temperature of 400 °C to optimize electrical properties with a steep metal-insulator transition. After growth, the sample were cooled to room temperature at 2 °C min−1. By optimizing the growth conditions, high crystal quality of VO2 epitaxial films was confirmed by a series of reciprocal space mapping data and a steep insulator-to-metal (and metal-to-insulator) transition at identical temperature (TIM ~20 °C, TMI ~14 °C) regardless of Pt NP coverage (0 ≤ tPt ≤ 5 s) on the TiO2 substrate.

Two Pt (50 nm) electrodes with 100 μm lateral width were patterned on top of a Pt-NP-embedded VO2 epitaxial film using photolithography and sputtering. A 5-μm gap was left between two electrodes; narrow electrode separation (~5 \(\mu\)m) allows the application of a sufficient electric field (~ 1.7 MV/m) to trigger electrically induced threshold ΙΜΤ switching using several volts.

2theta-omega scan and reciprocal space mapping (RSM) around the (112) TiO2 reflection were performed to characterize the crystal quality and lattice parameters in all Pt-NP-embedded VO2 epitaxial thin films using a high-resolution X-ray diffractometer (HRXRD, Bruker Discover 8) with Cu Kα1 radiation (λ = 0.15406 nm) at Materials Imaging & Analysis Center of POSTECH.

For the cross-sectional analysis on VO2 epitaxial films on Pt NP-TiO2 substrates, the thin foil was prepared by a dual-beam focused ion beam system (Helious Nanolab, Thermo Fisher Co., USA) through the [010] projection. HRTEM, STEM and atomic-scale EDS analyses were performed via the aberration-corrected STEM (JEM-ARM200F, JEOL, Japan) at 200 kV equipped with a fifth-order spherical aberration corrector (ASCOR, CEOS GmbH, Germany) and the dual100 mm2 Energy Dispersive X-ray Spectrometer detector (JED-2300T EDS, JEOL, Japan) at the Materials Imaging & Analysis Center of POSTECH. The electron probe for STEM observation was set to be ~70 pm; and the collection semi-angle was ranged from 54 to 216 mrad for High Angle Annular Dark Field (HAADF) imaging. The raw STEM data were filtered to reduce the background scanning noise by using Local 2D Difference Filter (Filters Pro, HREM Research Inc., Japan). EDS mapping signals were obtained during several tens of minutes by the multiple frame summation, up to ~4000 frames of 256 × 256 pixel-resolution; and the acquisition time per a single pixel was set to be 10 μsec. From the atomic scale TEM/STEM images, the strain analysis results were extracted by using the commercial plug-in software (GPA, HREM Research Inc., Japan).

Temperature-dependent sheet resistance was obtained to characterize metal-insulator transition characteristics for VO2 epitaxial films with different Pt coverage (0 ≤ tPt ≤ 5 s) by the Van der Pauw method. The electrical characteristics of the two-terminal VO2 electrical devices were measured using a semiconductor device analyzer (B1500A, Agilent) with a source measurement unit (SMU) and a waveform generator/fast measurement unit (WGFMU) in a temperature-variable probe station under Ar ambient conditions. Current–voltage characteristics were measured by sweeping the voltage from 0 V to 10 V with a 10 mV step using two SMUs on two electrodes. For pulse measurement, WGFMU was utilized to create the input voltage pulses and high-speed probe. Single pulse voltage was generated to monitor the threshold voltage pulse (Vth,pulse) by changing pulse the amplitude from 6.0 V to 9.0 V and a pulse duration of 100 μs. To investigate the influence of Pt NP coverage on this characteristic time (τ) of ‘memory’ of the metallic domain, a pump-probe experiment of VO2 threshold devices was carried out using consecutive input pulses (i.e., preceding super-threshold pump pulse (Vpulse > Vth,pulse) and second sub-threshold probe pulse (Vpulse < Vth,pulse)) with a pulse duration of 100 μs as a function of different pulse separation time (τ). Finally, for a high-pass filter (i.e., frequency discriminator), the super-threshold pulse is followed by a series of repetitive sub-threshold pulses separated by τ, which determines the frequency (f) of electrical stimuli, with a pulse duration of 100 μs.

The authors declare that all the data supporting the finding of this study are available within this article and its Supplementary Information files and are available from the corresponding author on reasonable request.

Basov, D. N., Averitt, R. D. & Hsieh, D. Towards properties on demand in quantum materials. Nat. Mater. 16, 1077–1088 (2017).

Article ADS CAS Google Scholar

Del Valle, J. et al. Subthreshold firing in Mott nanodevices. Nature 569, 388–392 (2019).

Article ADS Google Scholar

Brockman, J. S. et al. Subnanosecond incubation times for electric-field-induced metallization of a correlated electron oxide. Nat. Nanotechnol. 9, 453–458 (2014).

Article ADS CAS Google Scholar

Pickett, M. D., Medeiros-Ribeiro, G. & Williams, R. S. A scalable neuristor built with Mott memristors. Nat. Mater. 12, 114–117 (2013).

Article ADS CAS Google Scholar

Stoliar, P. et al. A leaky‐integrate‐and‐fire neuron analog realized with a Mott insulator. Adv. Funct. Mater. 27, 1604740 (2017).

Article Google Scholar

Oh, S. et al. Energy-efficient Mott activation neuron for full-hardware implementation of neural networks. Nat. Nanotechnol. 16, 680–687 (2021).

Article ADS CAS Google Scholar

Yang, Z., Ko, C. & Ramanathan, S. Oxide electronics utilizing ultrafast metal-insulator transitions. Annu. Rev. Mater. Res. 41, 337–367 (2011).

Article ADS CAS Google Scholar

Ngai, J. H., Walker, F. J. & Ahn, C. H. Correlated oxide physics and electronics. Annu Rev. Mater. Res. 44, 1–17 (2014).

Article ADS CAS Google Scholar

Yoon, H. et al. Reversible phase modulation and hydrogen storage in multivalent VO2 epitaxial thin films. Nat. Mater. 15, 1113–1119 (2016).

Article ADS CAS Google Scholar

Dagotto, E. Complexity in strongly correlated electronic systems. Science 309, 257–262 (2005).

Article ADS CAS Google Scholar

Lee, Y. et al. Large resistivity modulation in mixed-phase metallic systems. Nat. Commun. 6, 5959 (2015).

Jo, M. et al. Gate-induced massive and reversible phase transition of VO2 channels using solid-state proton electrolytes. Adv. Funct. Mater. 28, 1802003 (2018).

Qazilbash, M. M. et al. Mott transition in VO2 revealed by infrared spectroscopy and nano-imaging. Science 318, 1750–1753 (2007).

Article ADS CAS Google Scholar

Madan, H., Jerry, M., Pogrebnyakov, A., Mayer, T. & Datta, S. Quantitative mapping of phase coexistence in Mott-Peierls insulator during electronic and thermally driven phase transition. ACS Nano 9, 2009–2017 (2015).

Article CAS Google Scholar

Sohn, A., Kanki, T., Sakai, K., Tanaka, H. & Kim, D. W. Fractal nature of metallic and insulating domain configurations in a VO2 thin film revealed by kelvin probe force microscopy. Sci. Rep. 5, 10417 (2015).

Shabalin, A. G. et al. Nanoscale imaging and control of volatile and non-volatile resistive switching in VO2. Small 16, 2005439 (2020).

Del Valle, J. et al. Spatiotemporal characterization of the field-induced insulator-to-metal transition. Science 373, 907–911 (2021).

Article ADS Google Scholar

Sharoni, A., Ramirez, J. G. & Schuller, I. K. Multiple avalanches across the metal-insulator transition of vanadium oxide nanoscaled junctions. Phys. Rev. Lett. 101, 026404 (2008).

O’callahan, B. T. et al. Inhomogeneity of the ultrafast insulator-to-metal transition dynamics of VO2. Nat. Commun. 6, 6849 (2015).

Article ADS Google Scholar

Morin, F. Oxides which show a metal-to-insulator transition at the Neel temperature. Phys. Rev. Lett. 3, 34 (1959).

Article ADS CAS Google Scholar

Goodenough, J. B. The two components of the crystallographic transition in VO2. J. Solid State Chem. 3, 490–500 (1971).

Article ADS CAS Google Scholar

Fan, L. et al. Strain dynamics of ultrathin VO2 film grown on TiO2 (001) and the associated phase transition modulation. Nano Lett. 14, 4036–4043 (2014).

Article ADS CAS Google Scholar

Radu, I. P. et al. Switching mechanism in two-terminal vanadium dioxide devices. Nanotechnology 26, 165202 (2015).

Article ADS Google Scholar

Sood, A. et al. Universal phase dynamics in VO2 switches revealed by ultrafast operando diffraction. Science 373, 352 (2021).

Article ADS CAS Google Scholar

Kanki, T., Kawatani, K., Takami, H. & Tanaka, H. Direct observation of giant metallic domain evolution driven by electric bias in VO2 thin films on TiO2(001) substrate. Appl. Phys. Lett. 101, 243118 (2012).

Zimmers, A. et al. Role of thermal heating on the voltage induced insulator-metal transition in VO2. Phys. Rev. Lett, 110, 056601 (2013).

Shukla, N. et al. A steep-slope transistor based on abrupt electronic phase transition. Nat. Commun. 6, 7812 (2015).

Jian, J. et al. Broad range tuning of phase transition property in VO2 through metal-ceramic nanocomposite design. Adv. Funct. Mater. 29, 1903690 (2019).

He, Z. H. et al. Bidirectional tuning of phase transition properties in Pt:VO2 nanocomposite thin films. Nanoscale 12, 17886–17894 (2020).

Article CAS Google Scholar

Jeong, J. et al. Suppression of metal-insulator transition in VO2 by electric field–induced oxygen vacancy formation. Science 339, 1402–1405 (2013).

Article ADS CAS Google Scholar

Yoon, H., Park, J., Choi, S. Y., Lee, D. & Son, J. Facet‐dependent phase control by band filling and anisotropic electron–lattice coupling in HVO2 epitaxial films. Adv. Electron. Mater. 4, 1800128 (2018).

Article Google Scholar

Park, Y. et al. Directional ionic transport across the oxide interface enables low-temperature epitaxy of rutile TiO2. Nat. Commun. 11, 1401 (2020).

Jeong, J. et al. Giant reversible, facet-dependent, structural changes in a correlated-electron insulator induced by ionic liquid gating. Proc. Natl Acad. Sci. 112, 1013–1018 (2015).

Article ADS CAS Google Scholar

Park, J., Yoon, H., Sim, H., Choi, S. Y. & Son, J. Accelerated hydrogen diffusion and surface exchange by domain boundaries in epitaxial VO2 thin films. ACS Nano 14, 2533–2541 (2020).

Article CAS Google Scholar

Zheleva, T. S., Nam, O. H., Bremser, M. D. & Davis, R. F. Dislocation density reduction via lateral epitaxy in selectively grown GaN structures. Appl. Phys. Lett. 71, 2472–2474 (1997).

Article ADS CAS Google Scholar

Ohring, M. Materials Science of Thin Films. (Academic Press, 1991).

Hopster, H., Ibach, H. & Comsa, G. Catalytic oxidation of carbon monoxide on stepped platinum (111) surfaces. J. Catal. 46, 37–48 (1977).

Article CAS Google Scholar

Dohnalek, Z., Kim, J., Bondarchuk, O., White, J. M. & Kay, B. D. Physisorption of N2, O2, and CO on fully oxidized TiO2(110). J. Phys. Chem. B 110, 6229–6235 (2006).

Article CAS Google Scholar

Mellan, T. A. & Grau-Crespo, R. Density functional theory study of rutile VO2 surfaces. J. Chem. Phys. 137, 154706 (2012).

Article ADS Google Scholar

Joushaghani, A. et al. Voltage-controlled switching and thermal effects in VO2 nano-gap junctions. Appl. Phys. Lett. 104, 221904 (2014).

Article ADS Google Scholar

Choi, B. J., Chen, A. B. K., Yang, X. & Chen, I. W. Purely electronic switching with high uniformity, resistance tunability, and good retention in Pt-Dispersed SiO2 Thin Films for ReRAM. Adv. Mater. 23, 3847 (2011).

CAS PubMed Google Scholar

Claassen, J., Lu, J., West, K. & Wolf, S. Relaxation dynamics of the metal-semiconductor transition in VO2 thin films. Appl. Phys. Lett. 96, 132102 (2010).

Article ADS Google Scholar

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We acknowledge support for this work by the Basic Science Research Program (2020R1A4A1018935 (J.S., S.-Y.C.), 2020R1A2C2006389 (J.S.)) and Next-generation Intelligence Semiconductor Program (2022M3F3A2A03015405 (J.S.)) through the National Research Foundation of Korea (NRF) funded by the Ministry of Science and ICT.

Department of Materials Science and Engineering (MSE), Pohang University of Science and Technology (POSTECH), Pohang, Republic of Korea

Minguk Jo, Ye-Won Seo, Hyojin Yoon, Yeon-Seo Nam, Si-Young Choi & Junwoo Son

Department of Chemical Engineering and Materials Science (CEMS), University of Minnesota, Minneapolis, MN, USA

Hyojin Yoon

Department of Materials Science and Engineering (MSE), Seoul National University of Science and Technology (Seoultech), Seoul, Republic of Korea

Byung Joon Choi

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J.S. and M.J. conceived the idea and designed the study; H.Y. developed the growth process for Pt-nanoparticle-embedded VO2 epitaxial films; M.J., Y.-W.S., and H.Y. performed the growth of VO2 epitaxial films, X-ray diffraction, X-ray diffraction, and AFM. M.J. and Y.-W.S. performed the device fabrication and all electrical measurements and analyses with the guidance from B.J.C. and J.S.; Y.-S.N. and S.-Y.C. performed STEM analysis; J.S. and M.J. wrote the manuscript and all authors commented on it; J.S. directed the overall research.

Correspondence to Junwoo Son.

The authors declare no competing interests.

Nature Communications thanks the anonymous reviewers for their contribution to the peer review of this work.

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Jo, M., Seo, YW., Yoon, H. et al. Embedded metallic nanoparticles facilitate metastability of switchable metallic domains in Mott threshold switches. Nat Commun 13, 4609 (2022). https://doi.org/10.1038/s41467-022-32081-x

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Received: 06 September 2021

Accepted: 14 July 2022

Published: 10 August 2022

DOI: https://doi.org/10.1038/s41467-022-32081-x

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Embedded metallic nanoparticles facilitate metastability of switchable metallic domains in Mott threshold switches