A biological synapse type intrinsic self-assembly topological phase transition resistive memory and a preparation method thereof

Abstract

This invention relates to the fields of semiconductor information storage and artificial synaptic devices, specifically to a biological synaptic intrinsically self-assembled topological phase-change memristor and its fabrication method. The fabrication method includes: providing a substrate; depositing a bottom electrode; and depositing SrFeO on the bottom electrode. x The thin film serves as the storage medium layer; the storage medium layer undergoes heat treatment, including in-situ annealing and post-annealing. By controlling the oxygen pressure difference between in-situ and post-annealing, the single-component SrFeO is made more efficient. x An intrinsically self-assembled superlattice structure, characterized by alternating vertical and horizontal orientation regions of oxygen vacancy channels, spontaneously forms within the thin film. This structure restricts the formation sites of conductive filaments, significantly improving the consistency and stability of the device's resistive switching cycle. The process of this invention is simple, requiring no introduction of a second-phase material. The resulting memristor requires no electrical formation, exhibits a high on / off ratio, multi-level storage, and short-term synaptic plasticity, making it applicable to neuromorphic computing chips and artificial intelligence devices.

Description

Technical Field

[0001] This invention relates to the fields of semiconductor information storage and artificial synaptic devices, specifically to a biological synaptic intrinsically self-assembled topological phase-change memristor and its fabrication method. Background Technology

[0002] With the rapid development of artificial intelligence, big data analytics, and the Internet of Things (IoT) technologies, data-intensive computing tasks pose unprecedented challenges to the performance of computer hardware. Traditional von Neumann computing architectures, due to the physical separation of storage and computing units, result in frequent data transfers between the two, leading to significant energy consumption and latency—a phenomenon known as the "memory wall" bottleneck. To overcome this limitation, neuromorphic computing, inspired by the working mechanism of the human brain, has emerged. It utilizes electronic devices similar to biological synapses to achieve in-situ storage and updating of weights, offering advantages such as high parallelism, low power consumption, and adaptive learning.

[0003] Among the many electronic devices used to construct artificial synapses, memristors, with their simple metal-insulator-metal (MIM) sandwich structure, high integration density, and compatibility with CMOS processes, are considered strong contenders for next-generation non-volatile memory and neuromorphic computing chips. However, the operating mechanism of most memristor devices relies on the formation and breakage of conductive filaments (CFs) in the insulating dielectric layer. The growth and breakage of these filaments are inherently random; the specific location, morphology, and number of filaments are difficult to control precisely, whether in binary oxides or other media. This randomness directly leads to poor stability (C2C) of memristors during multiple cycles and difficulty in ensuring performance consistency (D2D) between different device units, severely impacting the computational accuracy and large-scale integrated applications of hardware neural networks.

[0004] To mitigate the aforementioned randomness issue, perovskite-structured transition metal oxides (such as SrFeO) exhibiting topological phase transition (TPT) characteristics are preferred. x , SrCoO x (etc.) have received widespread attention. Among them, strontium ferrite (SrFeO) has received widespread attention. x SFO) is an insulating calcium-iron-stone phase SrFeO at room temperature. 2.5 The Gibbs free energy difference between (BM-SFO) and the conductive perovskite phase SrFeO3 (PV-SFO) is extremely small, making it easy to achieve a low-power reversible phase transition through the migration of oxygen ions. This mechanism, based on the ordered transformation of the crystal structure, is theoretically more stable than random filament growth.

[0005] However, SFO materials still face structural challenges in practical applications. The unique layered stacked structure of BM-SFO naturally forms one-dimensional ordered oxygen vacancy channels, but in conventionally epitaxially grown thin films, these channels are usually horizontally oriented (parallel to the substrate surface). In memristors with vertical MIM structures, this forces oxygen ions to migrate longitudinally across the interlayer barrier, which not only increases the operating voltage but also easily induces uncontrollable lateral diffusion and stray conductive paths, again introducing instabilities in resistive switching behavior.

[0006] To address the issues of oxygen vacancy channel orientation and confined conductive paths, existing technologies have introduced traditional self-assembled vertically aligned nanocomposite structures (VANs). This method typically involves co-depositing two immiscible materials (such as SrTiO3 and MgO, Sm2O3, etc.), utilizing the lattice mismatch and strain between the two phases to induce the growth of vertically aligned nanopillar structures. These vertical phase boundaries act as rapid migration channels for oxygen ions, effectively confining the formation region of conductive filaments. Although traditional composite VANs technology has improved device performance to some extent, its fabrication process faces significant challenges: it requires precise selection of lattice-matched heteromaterial pairs, strict control of the stoichiometry between the two phases, and the thermodynamic growth windows of different materials often differ, which greatly increases the complexity and cost of high-quality thin film fabrication.

[0007] Therefore, the key breakthrough in solving the current problems of randomness and uniformity in memristors lies in how to spontaneously form an intrinsic self-assembly structure similar to VANs in a single-component material system without introducing a complex second phase, simply by controlling the process. This involves constructing an intrinsic self-assembly-like superlattice structure in which nanoscale oxygen vacancy channels are arranged alternately with vertical orientation (facilitating conduction) and horizontal orientation (facilitating blocking), thereby achieving precise spatial confinement of the formation position of conductive filaments. Summary of the Invention

[0008] In view of this, the present invention proposes a biological synaptic intrinsically self-assembled topological phase-change memristor and its fabrication method, based on a single-component SrFeO x The thin film, through a specific preparation process, spontaneously forms a superlattice-like stripe structure (intrinsic self-assembled structure) with periodic vertical and horizontal orientations inside, thereby effectively limiting the randomness of conductive filaments and improving the consistency and stability of the device's resistance switching cycle.

[0009] The technical solution of this invention is implemented as follows: In a first aspect, this invention proposes a method for fabricating a biological synaptic intrinsically self-assembled topological phase-change memristor, comprising the following steps: S1. Provide a substrate; S2. Deposit a bottom electrode on the substrate; S3, Deposit SrFeO on the bottom electrode x Thin film, to obtain the storage medium layer; S4. Perform heat treatment on the storage medium layer, the heat treatment including in-situ annealing and post-annealing performed sequentially.

[0010] Preferably, the oxygen pressure during in-situ annealing is higher than the oxygen pressure during post-annealing.

[0011] Preferably, the oxygen pressure during the in-situ annealing is 1.0 × 10⁻⁶. -2 mbar~5.0×10 -2 mbar; the oxygen pressure during the post-annealing is 1.0 × 10 mbar. -5 mbar ~ 1.0 × 10 -4 mbar.

[0012] Preferably, the in-situ annealing temperature is 650~750℃ and the time is 5~30min; the post-annealing temperature is 650~750℃ and the time is 5~30min.

[0013] Preferably, the deposition process in step S3 includes: a temperature of 650~750℃ and an oxygen pressure of 1.0×10⁻⁶. -2 mbar~5.0×10 -2 mbar, deposition time is 15~60 min.

[0014] Preferably, the deposition process in step S2 includes: a temperature of 650~750℃ and an oxygen pressure of 1.0×10⁻⁶. -1 mbar~2.0×10 -1 mbar.

[0015] Preferably, the bottom electrode comprises a SrRuO3 thin film; the substrate comprises a SrTiO3 single crystal substrate.

[0016] In a second aspect, the present invention provides a biological synaptic intrinsic self-assembled topological phase change memristor obtained by the preparation method described in the first aspect.

[0017] Preferably, the electrode comprises a substrate, a bottom electrode, a storage dielectric layer, and a top electrode stacked sequentially, wherein the storage dielectric layer is a single-component SrFeO. x The thin film has a superlattice-like structure formed by alternating vertical and horizontal orientation regions of oxygen vacancy channels.

[0018] Thirdly, the present invention provides a neuromorphic computing chip or artificial intelligence device, comprising the biosynaptic intrinsic self-assembled topological phase-change memristor described in the second aspect.

[0019] Compared with the prior art, the advantages of the present invention are as follows: (1) In this invention, after the strontium ferrite film is grown, in-situ annealing is first performed to improve the crystallinity of the film. Then, the temperature is kept constant and a suitable low oxygen pressure is applied for post-annealing to form a self-assembled superlattice structure, thus avoiding the problem of poor film crystallization caused by direct growth under low oxygen pressure.

[0020] (2) This invention does not require the introduction of a second phase material. It can form a vertical channel structure similar to VANs by using only a single component SFO under a specific vacuum annealing process, thus avoiding the problems of difficult lattice matching and difficult composition control of composite materials.

[0021] (3) The present invention uses vertical stripe regions to confine conductive filaments, and the device exhibits extremely low inter-device ripple and high consistency, and does not require an electrical formation process. It also has rich short-term memory characteristics and multi-level resistance states (4-bit). Attached Figure Description

[0022] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0023] Figure 1 This is a structural diagram of the SFO thin film of the present invention; Figure 2 This is a transmission electron microscope image of the cross-section of the SFO thin film prepared in Example 1; Figure 3 IV scan image of the SFO thin film prepared in Example 1; Figure 4 The resistance retention characteristic curves of the SFO thin film prepared in Example 1 for 16 intermediate states; Figure 5 The curve shows the short-term volatility of the SFO film prepared in Example 1 under voltage pulse stimulation. Figure 6 This is a transmission electron microscope image of the cross-section of the SFO thin film prepared in Example 2; Figure 7 IV scan image of the SFO thin film prepared in Example 2; Figure 8 This is a transmission electron microscope image of the cross-section of the SFO thin film prepared in Example 3; Figure 9 Transmission electron microscope image of the cross-section of the SFO thin film prepared in Comparative Example 1; Figure 10Transmission electron microscope image of the cross-section of the SFO thin film prepared in Comparative Example 2; Figure 11 Transmission electron microscope image of the cross-section of the SFO thin film prepared in Comparative Example 3; Figure 12 Transmission electron microscope image of the cross-section of the SFO thin film prepared in Comparative Example 4; Figure 13 The image shows the X-ray diffraction pattern of the SFO thin film prepared in Comparative Example 5. Detailed Implementation

[0024] The embodiments of the present invention are described in detail below. These embodiments are exemplary and intended to explain the present invention, and should not be construed as limiting the present invention.

[0025] It should be noted that the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features. Therefore, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature. Furthermore, in the description of this invention, unless otherwise stated, "a plurality of" means two or more.

[0026] In this document, the terms “containing,” “comprising,” or “including” are open-ended expressions, meaning they include the contents specified in this invention but do not exclude other aspects.

[0027] In this document, the terms “optional,” “optionally,” or “optional” generally refer to an event or condition that may, but may not, occur, and the description includes both cases in which the event or condition occurs and cases in which the event or condition does not occur.

[0028] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the protection scope of the present invention.

[0029] To achieve the above objectives, the present invention employs the following device structure, the schematic diagram of which is shown below. Figure 1 As shown, it includes: The substrate is composed of pure-phase SrTiO3 (STO) with the following crystal orientation: <100> Direction, dimensions 5×5×0.5mm; The bottom electrode (BE) is composed of pure-phase SrRuO3 (SRO) and its crystal orientation is... <100> The direction, and its thickness ranges from 25 to 100 nm; The storage medium layer is composed of pure-phase SrFeO. 2.5 (SFO), which has a self-assembled vertical superlattice structure composed of alternating vertical and horizontal stripe regions, and its crystal orientation should be... <100> The direction, and its thickness ranges from 20 to 50 nm; The top electrode (TE) is composed of pure-phase Pt or Au, with a thickness ranging from 25 to 100 nm and a size of 10 × 10 to 100 × 100 μm. 2 .

[0030] This invention provides a method for fabricating the above-mentioned memristor structure using pulsed laser deposition (PLD) technology, comprising the following steps: (1) The SrTiO3 (STO) substrate (purchased from Hefei Kejing Materials Technology Co., Ltd.) was cleaned with acetone, ethanol and deionized water. The substrate containing SrRuO3 (SRO) and SrFeO was then cleaned. 2.5 The target holder of the (SFO) target material is sent to the target stage in the cavity of the pulsed laser deposition equipment via a conveyor rod. The processed STO substrate is placed in the cavity of the pulsed laser deposition equipment, the target-substrate distance is set, and the substrate is heated at the same time. (2) Set the laser frequency and perform pre-sputtering to clean the target surface; (3) Set the laser intensity and frequency, use the laser to irradiate the SRO target to generate plasma plume, deposit SRO thin film on STO substrate, and monitor the change of vacuum in the cavity in real time; (4) Set the laser intensity and frequency, use the laser to irradiate the SFO target to generate plasma plume, deposit the SFO film on the SRO film, and monitor the change of vacuum degree in the cavity in real time. Keep the temperature and oxygen pressure in the vacuum cavity constant, and perform in-situ annealing on the substrate to repair the lattice defects generated during the film growth process and release the internal stress, thereby effectively improving the crystallinity of the SFO film and providing a lattice skeleton template with high crystal quality and structural stability for subsequent phase transition; (5) Keep the temperature inside the vacuum chamber constant and reduce the oxygen pressure inside the chamber to provide the thermodynamic driving force required for the topological phase transition. Under a relatively low oxygen partial pressure environment, the lattice oxygen inside the film is extracted to varying degrees, which promotes the topological phase transition of the SFO film and thus forms a self-assembled superlattice structure. The substrate obtained in step (4) is subjected to low oxygen post-annealing. After the film cools naturally to room temperature, the gas is stopped. (6) Turn off the pulsed laser deposition system, remove the substrate, and the self-assembled vertical superlattice SFO thin film is completed.

[0031] Specifically, the preparation method of this invention first utilizes in-situ annealing under high oxygen pressure to stabilize the thin film lattice structure, followed by low-oxygen post-annealing to extract lattice oxygen. Under this synergistic effect, a single-component SFO thin film can spontaneously form an intrinsic self-assembled superlattice structure with alternating vertical and horizontal orientations of oxygen vacancy channels through oxygen pressure regulation, without introducing a second-phase material or destroying the overall lattice framework. If only in-situ annealing is performed without low-oxygen pressure annealing, the oxygen content inside the SFO thin film will be too high, making it impossible to trigger a phase transition and form self-assembled superlattice fringes; conversely, if in-situ annealing is avoided and low-oxygen pressure annealing is performed directly, or if growth is performed directly under low oxygen pressure, excessive oxygen vacancy accumulation will destroy the lattice structure, resulting in poor film crystallization.

[0032] The device structure prepared by the above method is Au(Pt) / BM-SFO / SRO / STO.

[0033] Preferably, the process conditions for PLD deposition in step (3) include: a temperature of 650~750℃. o C, The cavity atmosphere is oxygen, and the pressure is 1.0 × 10⁻⁶. -1 ~2.0×10 -1 mbar, laser energy of 250~450 mJ, laser frequency of 1~8 Hz, and in-situ annealing time of 5~30 min.

[0034] Preferably, the process conditions for PLD deposition in step (4) include: a temperature of 650~750℃. o C, The cavity atmosphere is oxygen, and the pressure is 1.0 × 10⁻⁶. -2 ~5.0×10 -2 mbar, film deposition time is 15~60 min, in-situ annealing time is 5~25 min.

[0035] Preferably, the low-oxygen post-annealing process conditions in step (5) are: a temperature of 650~750°C. o C, The cavity atmosphere is oxygen, and the pressure is 1.0 × 10⁻⁶. -5 ~1.0×10 -4 mbar, in-situ annealing time is 5~30 min.

[0036] In this embodiment, the laser source used in the pulsed laser deposition system is a KrF excimer laser with a wavelength of 248 nm, and the angle between the target and the laser beam is approximately 45°.

[0037] Example 1

[0038] This embodiment provides a method for fabricating a biological synaptic intrinsically self-assembled topological phase-change memristor, including the following steps: (1) The SrTiO3 (STO) substrate was processed by first immersing it in acetone, alcohol and deionized water in sequence, and then cleaning it by ultrasonic vibration for 5 min each. Then, the substrate was fixed on the heating stage using conductive silver paste. The substrate, SrRuO3 (SRO) and SrFeO were then cleaned. 2.5 (SFO) The target material is delivered to the fixed support inside the pulsed laser deposition equipment cavity via a transfer rod. The distance between the target stage and the substrate is adjusted to 55 mm. The process continues until the molecular pump and mechanical pump pump pump 10... -7 After obtaining a vacuum below mbar, the substrate temperature is heated to 700 °C at a heating rate of 25 °C / min. (2) Set the laser frequency to 5 Hz and the laser energy to 250 mJ. Close the suction valve, open the oxygen valve, and manually adjust the bypass valve to adjust the oxygen pressure to (1.5±0.2)×10. -1 mbar; Adjust the baffle, use laser to irradiate the SRO and SFO targets to generate plasma plume, deposit for 12 min to clean the targets; (3) After pre-deposition, remove the baffle, maintain the laser frequency at 5 Hz and the laser energy at 250 mJ, and formally deposit the SRO thin film for 1 h. The deposition process is monitored in situ, and the temperature and pressure environment in the vacuum chamber are kept constant (temperature 700±5 ℃, pressure (1.0±0.2)×10). -1 After deposition (mbar), the substrate is annealed in situ for 15 minutes. (4) After SRO preparation, maintain the laser frequency at 5 Hz and the laser energy at 250 mJ, and formally deposit the SFO thin film for 30 min. The deposition process is monitored in situ, and the temperature and pressure environment in the vacuum chamber are kept constant (temperature 700±5 ℃, pressure (2.5±0.2)×10). -2 After deposition (mbar), the substrate is annealed in situ for 15 min. (5) After in-situ annealing, keep the temperature inside the chamber constant (700±5 ℃), reduce the oxygen flow rate, and make the oxygen pressure inside the chamber reach (5.0±0.2)×10 -5 After annealing for 25 minutes at mbar, heating was stopped, and the oxygen pressure remained constant. After the film cooled naturally to room temperature, the oxygen supply was stopped, the pulsed laser deposition system was turned off, the substrate was removed, and the self-assembled SFO film was completed.

[0039] See Figure 2 , Figure 2The image shows a transmission electron microscope (TEM) image of the cross-section of the SFO thin film prepared in Example 1. The TEM results show that the prepared SFO thin film has a clear vertical and horizontal alternating stripe structure with lattice spacings of 0.73 nm and 0.75 nm, respectively, confirming the formation of an intrinsic self-assembled structure.

[0040] The device prepared in Example 1 was subjected to electrical tests using a semiconductor analyzer (Agilent B1500A), such as... Figure 3 As shown, Figure 3 The image shows the IV scan of the SFO thin film prepared in Example 1. The device exhibits bipolar resistive switching behavior without electrical formation, with a SET voltage of approximately 1.5 V, a RESET voltage of approximately -2 V, an on / off ratio of 4400, and high consistency maintained over 100 cycles. Figure 4 As shown, Figure 4 The resistance retention characteristic curves for the 16 intermediate states of the SFO thin film prepared in Example 1 show that the device exhibits a 4-bit storage capability. Figure 5 As shown, Figure 5 The curves show the short-term volatility of the SFO film prepared in Example 1 under voltage pulse stimulation, illustrating that the device exhibits short-term volatility under write pulse stimulation.

[0041] Example 2

[0042] This embodiment provides a method for fabricating a biological synaptic intrinsically self-assembled topological phase-change memristor, including the following steps: (1) The SrTiO3 (STO) substrate was processed by first immersing it in acetone, alcohol and deionized water in sequence, and then cleaning it by ultrasonic vibration for 5 minutes each. Then, the substrate was fixed on the heating stage using conductive silver paste. The substrate, SrRuO3 (SRO) and SrFeO were then subjected to ultrasonic cleaning. 2.5 (SFO) The target material is delivered to the fixed support inside the pulsed laser deposition equipment cavity via a transfer rod. The distance between the target stage and the substrate is adjusted to 55 mm. The process continues until the molecular pump and mechanical pump pump pump 10... -7 After obtaining a vacuum below mbar, the substrate temperature is heated to 650 °C at a heating rate of 25 °C / min. (2) Set the laser frequency to 5 Hz and the laser energy to 250 mJ. Close the suction valve, open the oxygen valve, and manually adjust the bypass valve to adjust the oxygen pressure to (1.5±0.2)×10. -1 mbar; Adjust the baffle, use laser to irradiate the SRO and SFO targets to generate plasma plume, deposit for 12 min to clean the targets; (3) After pre-deposition, remove the baffle, maintain the laser frequency at 5 Hz and the laser energy at 250 mJ, and formally deposit the SRO thin film for 15 min. Monitor the deposition process in situ, keeping the temperature and pressure environment inside the vacuum chamber constant (temperature 650±5 ℃, pressure (2.0±0.2)×10). -1 mbar), after deposition, the substrate is annealed in situ for 15 min; (4) After SRO preparation, the laser frequency was kept at 5 Hz and the laser energy at 250 mJ. The SFO film was then deposited for 15 min. The deposition process was monitored in situ, and the temperature and pressure in the vacuum chamber were kept constant (temperature 650±5 ℃, pressure (5.0±0.2)×10). -2 mbar), after deposition, the substrate is annealed in situ for 5 min; (5) After in-situ annealing, keep the temperature inside the chamber constant (650±5 ℃) and reduce the oxygen flow rate so that the oxygen pressure inside the chamber reaches (1.0±0.2)×10 -4 After annealing for 30 minutes at mbar, heating was stopped, and the oxygen pressure remained constant. After the film cooled naturally to room temperature, the oxygen supply was stopped, the pulsed laser deposition system was turned off, the substrate was removed, and the self-assembled SFO film was completed.

[0043] See Figures 6-7 , Figure 6 This is a transmission electron microscope image of the cross-section of the SFO thin film prepared in Example 2; Figure 7 The image shows an IV scan of the SFO film prepared in Example 2. The structure of the SFO film prepared in Example 2 is the same as that in Example 1, except that the thickness of the SFO film is 20 nm and the on / off ratio of the device is around 240, indicating that a self-assembled film can be formed even with a short deposition time and the device has good resistance switching cycle stability.

[0044] Example 3

[0045] This embodiment provides a method for fabricating a biological synaptic intrinsically self-assembled topological phase-change memristor, including the following steps: (1) The SrTiO3 (STO) substrate was processed by first immersing it in acetone, alcohol and deionized water in sequence, and then cleaning it by ultrasonic vibration for 5 min each. Then, the substrate was fixed on the heating stage using conductive silver paste. The substrate, SrRuO3 (SRO) and SrFeO were then cleaned. 2.5 (SFO) The target material is delivered to the fixed support inside the pulsed laser deposition equipment cavity via a transfer rod. The distance between the target stage and the substrate is adjusted to 55 mm. The process continues until the molecular pump and mechanical pump pump pump 10... -7After obtaining a vacuum below mbar, the substrate temperature is heated to 750 °C at a heating rate of 25 °C / min. (2) Set the laser frequency to 5 Hz and the laser energy to 250 mJ. Close the suction valve, open the oxygen valve, and manually adjust the bypass valve to adjust the oxygen pressure to (1.5±0.2)×10. -1 mbar; Adjust the baffle, use laser to irradiate the SRO and SFO targets to generate plasma plume, deposit for 12 min to clean the targets; (3) After pre-deposition, remove the baffle, maintain the laser frequency at 5 Hz and the laser energy at 250 mJ, and formally deposit the SRO thin film for 15 min. Monitor the deposition process in situ, keeping the temperature and pressure environment inside the vacuum chamber constant (temperature 750±5 ℃, pressure (1.0±0.2)×10). -1 mbar), after deposition, the substrate is annealed in situ for 15 min; (4) After SRO preparation, the laser frequency was kept at 5 Hz and the laser energy at 250 mJ. The SFO film was then deposited for 60 min. The deposition process was monitored in situ, and the temperature and pressure in the vacuum chamber were kept constant (temperature 750±5 ℃, pressure (1.0±0.2)×10). -2 mbar), after deposition, the substrate is annealed in situ for 25 min; (5) After in-situ annealing, keep the temperature inside the chamber constant (750±5 ℃) and reduce the oxygen flow rate so that the oxygen pressure inside the chamber reaches (1.0±0.2)×10 -5 After annealing for 5 minutes at mbar, heating was stopped, and the oxygen pressure remained constant. After the film cooled naturally to room temperature, the oxygen supply was stopped, the pulsed laser deposition system was turned off, and the substrate was removed. The self-assembled SFO film preparation was completed.

[0046] See Figure 8 , Figure 8 The image shows a cross-sectional transmission electron microscope image of the SFO film prepared in Example 3. The structure of the SFO film prepared in Example 3 is the same as that in Example 1, except that the thickness of the SFO film is 108 nm and the boundaries between layers are clear, indicating that the film interface still has high flatness and exhibits a good epitaxial structure even with a long deposition time.

[0047] Comparative Example 1 The difference between this comparative example and Example 1 is that the annealing oxygen pressure in step (5) is changed to (5.0±0.2)×10. -4 mbar, other preparation conditions are the same as in Example 1.

[0048] The SFO thin film prepared in Comparative Example 1 was characterized using transmission electron microscopy, mainly to determine the structure of the SFO thin film, such as... Figure 9 As shown in the figure, the SFO layer exhibits indistinct lateral and vertical superlattice-like fringes, and most areas still retain an oxygen-rich perovskite structure, indicating that the (5.0±0.2)×10⁻⁶ saturated perovskite structure in Comparative Example 1... -4 High-pressure oxygen annealing (mbar) makes it difficult for SFO films to produce a pure calcium iron BM phase.

[0049] Comparative Example 2 The difference between this comparative example and Example 1 is that the annealing oxygen pressure in step (5) is changed to (5.0±0.2)×10. -6 mbar, other preparation conditions are the same as in Example 1.

[0050] The SFO thin film prepared in Comparative Example 2 was characterized using transmission electron microscopy, mainly to determine the structure of the SFO thin film, such as... Figure 10 Therefore, a distinct amorphous layer appeared on the upper surface of the SFO film, indicating that the (5.0 ± 0.2) × 10⁻⁶ layer in Comparative Example 2... -6 Annealing at a low oxygen pressure (mbar) causes a large amount of lattice oxygen to be extracted from the SFO film, resulting in damage to the film's lattice structure.

[0051] Comparative Example 3 The difference between this comparative example and Example 1 is that after the deposition in step (4) is completed, in-situ annealing is not performed, but low oxygen pressure annealing in step (5) is performed directly. Other preparation conditions are the same as in Example 1.

[0052] The SFO thin film prepared in Comparative Example 3 was characterized using transmission electron microscopy, mainly to determine the structure of the SFO thin film. Figure 11 As can be seen, there are obvious voids inside the SFO film, indicating that in Comparative Example 3, the SFO film lattice will be damaged if the lattice is directly annealed under low oxygen pressure without in-situ heat preservation repair.

[0053] Comparative Example 4 The difference between this comparative example and Example 1 is that after the deposition in step (4) is completed, in-situ annealing is performed, but the low oxygen pressure annealing in step (5) is not performed. Other preparation conditions are the same as in Example 1.

[0054] The SFO thin film prepared in Comparative Example 4 was characterized using transmission electron microscopy, mainly to determine the structure of the SFO thin film. Figure 12 As can be seen, the SFO film has good crystallization, but there are no superlattice-like fringes. This indicates that in Comparative Example 4, annealing in situ without low-oxygen-pressure annealing will result in an excessively high oxygen content inside the SFO film, thus preventing the formation of a self-assembled superlattice-like structure.

[0055] Comparative Example 5 The difference between this comparative example and Example 1 is that after the deposition in step (4) is completed, neither in-situ annealing nor low-oxygen pressure annealing in step (5) is performed. Other preparation conditions are the same as in Example 1.

[0056] The SFO thin film prepared in Comparative Example 5 was characterized using X-ray diffraction (XRD), mainly to determine the phase composition of the SFO thin film. Figure 13 As can be seen from the spectrum, there are no diffraction peaks of the SFO film, indicating poor crystallinity of the reaction film. This suggests that neither in-situ annealing nor low-oxygen-pressure annealing will greatly damage the crystallinity of the SFO film.

[0057] In summary, the pulsed laser deposition method of this invention offers a simple fabrication process with adjustable parameters. All substrates used are commercially available and readily accessible, exhibiting good reproducibility. The prepared single-component SFO thin film can spontaneously form a self-assembled vertical superlattice with vertically and horizontally oriented oxygen vacancy channels during fabrication through oxygen pressure regulation. This allows for precise spatial confinement of the conductive filament formation positions, representing a key breakthrough in addressing the current problems of randomness and uniformity in memristors.

[0058] The embodiments described above are some, but not all, of the embodiments of the present invention; the detailed description of the embodiments of the present invention is not intended to limit the scope of the claimed invention, but merely to illustrate selected embodiments of the invention; all other embodiments obtained by those skilled in the art based on the embodiments of the present invention without inventive effort are within the scope of protection of the present invention.

Claims

1. A method for fabricating a biological synaptic intrinsically self-assembled topological phase-change memristor, characterized in that, Includes the following steps: S1. Provide a substrate; S2. Deposit a bottom electrode on the substrate; S3, Deposit SrFeO on the bottom electrode x Thin film, to obtain the storage medium layer; S4. Perform heat treatment on the storage medium layer, the heat treatment including in-situ annealing and post-annealing performed sequentially.

2. The preparation method according to claim 1, characterized in that, The oxygen pressure during in-situ annealing in step S4 is higher than the oxygen pressure during post-annealing.

3. The preparation method according to claim 1, characterized in that, The oxygen pressure for in-situ annealing in step S4 is 1.0 × 10⁻⁶. -2 mbar~5.0×10 -2 mbar; the oxygen pressure during the post-annealing is 1.0 × 10 mbar. -5 mbar ~ 1.0 × 10 -4 mbar.

4. The preparation method according to claim 1, characterized in that, The in-situ annealing temperature in step S4 is 650~750℃ and the time is 5~25min; the post-annealing temperature is 650~750℃ and the time is 5~30min.

5. The preparation method according to claim 1, characterized in that, The deposition process in step S3 includes: a temperature of 650~750℃ and an oxygen pressure of 1.0×10⁻⁶. -2 mbar~5.0×10 -2 mbar, deposition time is 15~60 min.

6. The preparation method according to claim 1, characterized in that, The deposition process in step S2 includes: a temperature of 650~750℃ and an oxygen pressure of 1.0×10⁻⁶. -1 mbar~2.0×10 -1 mbar.

7. The preparation method according to claim 1, characterized in that, The bottom electrode comprises a SrRuO3 thin film; the substrate comprises a SrTiO3 single crystal substrate.

8. A biosynaptic intrinsically self-assembled topological phase-change memristor obtained by the preparation method according to any one of claims 1 to 7.

9. The biosynaptic intrinsically self-assembled topological phase-change memristor according to claim 8, characterized in that, It includes a substrate, a bottom electrode, a storage dielectric layer, and a top electrode stacked sequentially, wherein the storage dielectric layer is a single-component SrFeO. x Thin film, which has an intrinsic self-assembled superlattice structure with alternating vertical and horizontal orientation regions of oxygen vacancy channels inside.

10. A neuromorphic computing chip or artificial intelligence device, characterized in that, It includes the biosynaptic intrinsic self-assembled topological phase change memristor as described in any one of claims 8 to 9.

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