CN114883487A - Self-forming topological phase change nano memory device structure, and preparation and application thereof - Google Patents

Self-forming topological phase change nano memory device structure, and preparation and application thereof Download PDF

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CN114883487A
CN114883487A CN202210467671.3A CN202210467671A CN114883487A CN 114883487 A CN114883487 A CN 114883487A CN 202210467671 A CN202210467671 A CN 202210467671A CN 114883487 A CN114883487 A CN 114883487A
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sxo
layer
thin film
nano
substrate
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程伟明
苏睿
肖睿子
陈家宝
缪向水
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Huazhong University of Science and Technology
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    • H—ELECTRICITY
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    • H10N70/00—Solid-state devices without a potential-jump barrier or surface barrier, and specially adapted for rectifying, amplifying, oscillating or switching
    • H10N70/011—Manufacture or treatment of multistable switching devices
    • H—ELECTRICITY
    • H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
    • H10N—ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
    • H10N70/00—Solid-state devices without a potential-jump barrier or surface barrier, and specially adapted for rectifying, amplifying, oscillating or switching
    • H10N70/20—Multistable switching devices, e.g. memristors
    • H10N70/231—Multistable switching devices, e.g. memristors based on solid-state phase change, e.g. between amorphous and crystalline phases, Ovshinsky effect
    • H—ELECTRICITY
    • H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
    • H10N—ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
    • H10N70/00—Solid-state devices without a potential-jump barrier or surface barrier, and specially adapted for rectifying, amplifying, oscillating or switching
    • H10N70/20—Multistable switching devices, e.g. memristors
    • H10N70/24—Multistable switching devices, e.g. memristors based on migration or redistribution of ionic species, e.g. anions, vacancies
    • H—ELECTRICITY
    • H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
    • H10N—ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
    • H10N70/00—Solid-state devices without a potential-jump barrier or surface barrier, and specially adapted for rectifying, amplifying, oscillating or switching
    • H10N70/801—Constructional details of multistable switching devices
    • H10N70/881—Switching materials
    • H10N70/883—Oxides or nitrides
    • H10N70/8836—Complex metal oxides, e.g. perovskites, spinels

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Abstract

The invention belongs to the technical field of semiconductor information storage and artificial synapse devices, and particularly relates to a self-formed topological phase change nano memory device structure, and preparation and application thereof. Active metal nano particles grow on an SXO (X ═ Fe, Co) film, partial O ions in the SXO are absorbed by utilizing the property that the metal nano particles are easy to be oxidized, the SXO film below the metal nano particles is in an anoxic state at the moment, a BM-SXO phase blocking layer with higher resistance is formed, the size of the PV-SXO conductive wire is determined by the size of the metal nano particles, and the direction of the PV-SXO conductive wire is limited to be vertical to the in-plane direction of the film to a certain extent, so that the consistency and the reliability of the oxide-based memory device are realized.

Description

Self-forming topological phase change nano memory device structure, and preparation and application thereof
Technical Field
The invention belongs to the technical field of semiconductor information storage and artificial synapse devices, and particularly relates to a self-formed topological phase change nano memory device structure, and preparation and application thereof.
Background
In recent years, the concept of "topology" has been introduced into the field of material research, and when a part of the constituent elements in the material is extracted, the crystal structure can still be kept stable, and the corresponding physical and chemical structures can be changed to a certain extent, and such materials are called topological phase change materials. In which SrFeO is used 3 (SFO) and SrCoO 3 The transition metal-based perovskite-type material represented by (SCO) has obvious topological phase change property, such as SrFeO 3 When the material has a relatively complete Perovskite type crystal structure (PV-SFO), holes exist on an O2 p orbital, the charge transfer energy delta eff is negative, and the SFO has no band gap, so that the PV-SFO shows a metal property. When SrFeO 3 Lose a part of cation, change the stoichiometric ratio to SrFeO 2.5 The crystal structure thereof was changed to a Brownmillerite type (BM-SFO) in which the O2 p orbital does not occupy the Fe 3d orbital and the charge transfer energy Δ eff is positive, so that the bandgap width of BM-SFO was 2eV, and in which the SFO exhibited a semiconductor property. Due to the characteristics, topological phase change materials such as SFO and the like are widely applied to research on memristors and ferroelectric memories (large resistance value switching is generated in the process of switching metal and semiconductor properties), and the conduction mechanism of a corresponding device is mainly that an external electric field causes PV-SFO metal conductive wires to be locally formed in BM-SFO semiconductor matrixes, so that the resistance value switching of the device is realized. Therefore, the control of the direction and the size of the PV-SFO is the key for regulating and controlling the circulation stability characteristics of the SFO-based memristor and the SCO-based memristor.
At present, researches on regulation and control of the PV-SFO conductive wire mainly focus on changing the growth crystal direction of a substrate, reducing the size of an electrode, designing a T-shaped electrode by etching a trepan, and the like.
Disclosure of Invention
Aiming at the defects of the prior art, the invention provides a self-forming topological phase change nano memory device structure, and preparation and application thereof, and solves the technical problems that the in-plane direction migration of a conductive wire cannot be controlled, the process limit exists, the functional layer is damaged and the like by a PV-SFO conductive wire regulation and control method in the prior art.
In order to achieve the above object, the present invention provides a method for preparing a self-forming topological phase-change nano memory device structure, comprising the following steps:
(1) preparing a thin film lower electrode layer on a substrate;
(2) preparing SrXO on the thin film lower electrode layer m The film functional layer, wherein X is Fe or Co, and m is more than or equal to 2.85 and less than 3;
(3) transferring the polystyrene nano microsphere mixed solution dispersed by the solvent to the surface of the film functional layer, standing to volatilize the solvent, and obtaining the film functional layer paved with single-layer polystyrene nano microspheres;
(4) depositing an active metal layer on the thin film functional layer paved with the single-layer polystyrene nano microspheres; then cleaning the obtained substrate, and removing the polystyrene nano microspheres and redundant metal on the surface of the substrate to obtain the substrate with the patterned nano metal particles on the surface;
(5) depositing an upper electrode layer on the substrate prepared with the patterned nano-metal particles;
(6) and applying positive bias on the upper electrode layer to enable topological phase change to be generated inside the thin film functional layer to form a BM-SXO barrier layer.
Preferably, the substrate is SrTiO 3 A substrate of said SrTiO 3 The substrate is SrTiO obtained by ultrasonic cleaning in acetone and ethanol in sequence 3 A substrate.
Preferably, the lower electrode layer in the step (1) is SrRuO 3 A thin film lower electrode layer formed on the SrTiO layer by a pulsed laser deposition process 3 Preparation of SrRuO on a substrate 3 The specific deposition process conditions of the film lower electrode layer are as follows: the temperature is 650-750 ℃, the atmosphere of the cavity is oxygen, the air pressure is 10-15 Pa, the laser energy is 250-450 mJ, the laser frequency is 1-8 Hz, and the vacuum degree is 1 multiplied by 10 -6 ～1×10 -5 Pa, the distance between the substrate and the target is 40-60 mm.
Preferably, step (3) prepares SrXO on the thin film lower electrode layer using a pulsed laser deposition process m The specific deposition process conditions of the thin film functional layer are as follows: the temperature is 650-700 ℃, the atmosphere of the cavity is oxygen, the air pressure is 5-10 Pa, the laser energy is 250-450 mJ, the laser frequency is 1-8 Hz, and the vacuum degree is 1 multiplied by 10 -6 ～1×10 -5 Pa, the distance between the substrate and the target material is 40-60 mm, and the deposition time is 600-1800 s.
Preferably, the solvent in the step (3) is an aqueous solution of ethanol, and the mass ratio of the polystyrene nano-microspheres, ethanol and water in the solvent-dispersed polystyrene nano-microsphere mixed solution is 1: (15-25): (10-15).
Preferably, a surfactant is added into the solvent-dispersed polystyrene nano-microsphere mixed solution to enhance the surface tension of the polystyrene nano-microspheres, so that the degree of compactness of a spherical film formed by aggregation of the polystyrene nano-microspheres is increased; then placing the substrate obtained in the step (2) below the spherical membrane, so that the spherical membrane is transferred to the surface of the substrate; and standing to volatilize the solvent to obtain the thin film functional layer paved with the single-layer polystyrene nano microspheres.
Preferably, 1 to 5 drops of aqueous solution of sodium dodecyl sulfate with the concentration of 2 to 4 weight percent is added into every 150mL of the solvent-dispersed polystyrene nano microsphere mixed solution.
Preferably, the active metal in the step (4) is Al, Fe, Ti or Cu; depositing an active metal layer on the thin film functional layer paved with the single-layer polystyrene nano microspheres by an electron beam evaporation process; the specific process conditions are as follows: the temperature is room temperature, the growth rate is 0.08-0.15nm/s, and the deposition time is 180-220 s.
Preferably, in the step (4), the obtained substrate is sequentially washed by toluene, acetone, isopropanol and deionized water, and the polystyrene nano-microspheres and the redundant metal on the surface of the substrate are removed.
Preferably, the upper electrode layer of step (5) is metal Pt, TiN, W or Au; preferably, a magnetron sputtering or electron beam evaporation process is used to deposit the upper electrode layer on the substrate with the patterned nano-metal particles on the surface.
Preferably, in the step (6), a positive bias voltage of 1-5V is applied to the upper electrode layer, so that topological phase change is generated inside the thin film functional layer to form a BM-SXO barrier layer.
According to another aspect of the invention, a self-forming topological phase change nano memory device structure is provided, which comprises SrTiO from bottom to top 3 Substrate, SrRuO 3 Thin film bottom electrode layer, mixed SXO thin film functionA layer, a patterned layer of nano-metal oxide particles, and an upper electrode layer; wherein the content of the first and second substances,
the mixed SXO film functional layer comprises a mixed film functional layer which is obtained by orderly and staggered distribution of nanoscale PV-SXO conductive wires vertical to the in-plane direction of the film and a BM-SXO barrier layer; the patterned layer of nano-metal oxide particles comprises patterned nano-metal oxide particles; the nanometer metal oxide particles are aligned with the BM-SXO barrier layer in the mixed thin film functional layer, so that topological phase change switching does not occur in the BM-SXO barrier layer region; gaps among the nano metal oxide particles are aligned with the PV-SXO conductive wires in the mixed thin film functional layer;
when the device is used, the oxygen content of PV-SXO in the mixed thin film functional layer is regulated and controlled by changing the direction of an electric field applied between the lower electrode layer and the upper electrode layer of the device, so that the resistance value of the thin film functional layer is regulated and controlled.
Wherein PV-SXO is SrXO m The BM-SXO is SrXO 2.5 (ii) a Wherein X is Fe or Co, and m is more than or equal to 2.85 and less than 3.
Preferably, the thickness of the mixed SXO thin film functional layer is 10-30 nm.
According to another aspect of the invention, an application of the memory device structure is provided, which is used for preparing a memristor or a ferroelectric memory.
Generally, compared with the prior art, the above technical solution conceived by the present invention has the following beneficial effects:
(1) the active metal nano particles are grown on the SXO (X ═ Fe, Co) film, partial O ions in the SXO are absorbed by utilizing the property that the metal nano particles are easy to be oxidized, the SXO film below the metal nano particles is in an anoxic state at the moment, a BM-SXO phase blocking layer with higher resistance is formed, the size of the PV-SXO conductive wire is determined by the size of the metal nano particles, and the direction of the PV-SXO conductive wire is limited to be vertical to the in-plane direction of the film to a certain extent, so that the consistency and the reliability of the oxide-based memory device are realized.
(2) The self-forming topological phase change material nano memory device structure provided by the invention has a vertical barrier layer with a nano scale, effectively inhibits the formation of a conductive wire in the in-plane direction, and effectively improves the consistency of the device.
(3) The BM-SXO barrier layer in the self-formed topological phase change material nano memory device structure is naturally formed by oxygen absorption of metal nano particles, and the metal nano particles are oxidized into metal oxide MO x The (M ═ Al/Fe/Cu/Ti, etc.) amorphous layer can provide a horizontal barrier effect, and further prevent the random oxidation of the conductive wire.
(4) The conductive wire with a smaller size formed by the prior art depends on small-size etching, the process cost is high, and the functional layer film is easy to damage.
(5) The self-forming topological phase change nano memory device structure provided by the invention can be used for preparing a memristor and a ferroelectric memory.
In conclusion, the self-forming nano-size memory device is prepared by evaporating and plating nano metal particles on the SXO film, the problem that the size of a conductive wire of an oxide memristor or a ferroelectric memory is uncontrollable can be effectively solved, and the uniformity and the reliability of the device can be remarkably improved.
Drawings
FIG. 1 is a schematic view of the structure of step (2) in example 1.
FIG. 2 is a schematic view of the structure of step (3) in example 1.
FIG. 3 is a schematic structural view of step (4) in example 1.
FIG. 4 is a schematic view of the structure of step (5) in example 1.
FIG. 5 is a schematic view of the structure of step (6) in example 1.
FIG. 6 is a schematic view of the structure of step (7) in example 1.
FIG. 7 is a schematic view of the structure of step (8) in example 1.
FIG. 8 shows Pt/Al nanoparticles/SrXO prepared in example 1 m /SrRuO 3 And (4) a structural principle schematic diagram of an initial state of the memristor.
FIG. 9 shows Pt/Al nanoparticles/SrXO prepared in example 1 m /SrRuO 3 And forming a principle schematic diagram of a nanoscale barrier layer after the memristor is formed.
Detailed Description
In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention is described in further detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.
The invention provides a preparation method of a self-forming topological phase change nano memory device structure, which comprises the following steps:
(1) preparing a thin film lower electrode layer on a substrate;
(2) preparing SrXO on the thin film lower electrode layer m The film functional layer, wherein X is Fe or Co, and m is more than or equal to 2.85 and less than 3;
(3) transferring the polystyrene nano microsphere mixed solution dispersed by the solvent to the surface of the film functional layer, standing to volatilize the solvent, and obtaining the film functional layer paved with single-layer polystyrene nano microspheres;
(4) depositing an easily oxidized nano metal layer on the thin film functional layer paved with the single-layer polystyrene nano microspheres; then cleaning the obtained substrate, and removing the polystyrene nano microspheres and redundant metal on the surface of the substrate to obtain the substrate with the patterned nano metal particles on the surface;
(5) depositing an upper electrode layer on the substrate with the patterned nano-metal particles prepared on the surface;
(6) applying positive bias on the upper electrode layer to generate topological phase change in the thin film functional layer to form a BM-SXO barrier layer, wherein the BM-SXO is SrXO 2.5 Wherein X is Fe or Co.
The substrate, the upper electrode and the lower electrode of the memory device can be made of the substrate and the electrode materials commonly used in the prior art. One of the deposition processes in the prior art can be selected according to the requirements in the preparation processes in the step (1), the step (2), the step (4) and the step (5), and the preparation processes include but are not limited to one of magnetron sputtering, electron beam evaporation, Atomic Layer Deposition (ALD), Molecular Beam Epitaxy (MBE), Pulsed Laser Deposition (PLD) and the like.
In some embodiments, the substrate is SrTiO 3 A substrate of said SrTiO 3 The substrate is SrTiO obtained by ultrasonic cleaning in acetone and ethanol in sequence 3 A substrate.
In some embodiments, the lower electrode layer of step (1) is SrRuO 3 A thin film lower electrode layer formed on the SrTiO layer by a pulsed laser deposition process 3 Preparation of SrRuO on a substrate 3 The specific deposition process conditions of the film lower electrode layer are as follows: the temperature is 650-750 ℃, the atmosphere of the cavity is oxygen, the air pressure is 10-15 Pa, the laser energy is 250-450 mJ, the laser frequency is 1-8 Hz, and the vacuum degree is 1 multiplied by 10 -6 ～1×10 -5 Pa, the distance between the substrate and the target is 40-60 mm.
In some embodiments, step (3) prepares SrXO on the thin film lower electrode layer using a pulsed laser deposition process m The specific deposition process of the film functional layer comprises the following steps: the temperature is 650-700 ℃, the atmosphere of the cavity is oxygen, the air pressure is 5-10 Pa, the laser energy is 250-450 mJ, the laser frequency is 1-8 Hz, and the vacuum degree is 1 multiplied by 10 -6 ～1×10 -5 Pa, the distance between the substrate and the target material is 40-60 mm, and the deposition time is 600-1800 s.
In some embodiments, the solvent in step (3) is an aqueous solution of ethanol, and the mass ratio of the polystyrene nanospheres, ethanol and water in the solvent-dispersed polystyrene nanosphere solution is 1: (15-25): (10-15).
In some embodiments, 5g of polystyrene nanospheres are dispersed in 100mL of deionized water, then 60mL of ethanol or other alcohol chemical reagent is added as a dispersing agent (since the density of the polystyrene spheres is 1.52, which is greater than that of water, the alcohol chemical reagent can improve the surface tension of the polystyrene spheres so that the polystyrene spheres are partially immersed in water without sinking to ensure the uniformity of the solution), and finally the diluted and dispersed polystyrene nanospheres are further subjected to ultrasonic dispersion to obtain a uniform solvent-dispersed polystyrene nanosphere mixed solution.
In some embodiments, the slide is inserted into a petri dish at an angle of about 30 ° and deionized water is placed in the petri dish. And slowly dripping a proper amount of the organic solvent dispersed polystyrene nano microsphere mixed solution on an inclined glass slide, uniformly spreading the polystyrene nano microspheres on the surface of deionized water by guiding the glass slide, and dripping 1-5 drops of Sodium Dodecyl Sulfate (SDS) aqueous solution with the concentration of 2-4 wt% after the solution is completely spread to further strengthen the surface tension of the polystyrene nano microspheres so that a film formed by aggregation of the polystyrene nano microspheres is more compact. After the steps are finished, the substrate obtained in the step (2) is stretched into the lower part of the polystyrene nanometer microsphere membrane by using tweezers, so that the microsphere membrane is transferred to the surface of the substrate. And then, placing the substrate coated with the mixed solution of the polystyrene nano microsphere spherical membrane in a clean culture dish, drying at room temperature, and completely attaching the self-assembled polystyrene nano microsphere spherical membrane on the surface of the substrate after the solvent is completely volatilized to obtain the thin film functional layer paved with the single-layer polystyrene nano microspheres.
The active metal in the step (4) includes but is not limited to Al, Fe, Ti or Cu; in some embodiments, an oxidizable nano metal layer is deposited on the thin film functional layer paved with the single-layer polystyrene nano microspheres through an electron beam evaporation process; the specific process conditions are as follows: the temperature is room temperature, the growth rate is 0.08-0.15nm/s, and the deposition time is 180-220 s.
In some embodiments, in step (4), the obtained substrate is sequentially washed with toluene, acetone, isopropanol and deionized water to remove the polystyrene nanoparticles and the excess metal on the surface of the substrate. And sequentially soaking the obtained substrate in toluene, acetone and isopropanol, removing the polystyrene nano microspheres by using the toluene (at the moment, redundant metals are removed together), and cleaning by using the acetone, the isopropanol and deionized water to remove residual organic matters so as to remove the polystyrene nano microspheres and the redundant metals on the surface of the substrate. In the deposition process in the step (4), the polystyrene nano-microspheres laid in a single layer are equivalent to a mask, when metal Al, Fe, Ti or Cu is deposited on the surface of the polystyrene nano-microspheres laid in a single layer by adopting an electron beam evaporation process, the metal Al, Fe, Ti or Cu is only deposited between the polystyrene nano-microspheres laid in a single layer and the microspheres, even if excessive metal is deposited, the metal can be cleaned along with the polystyrene microspheres during cleaning, and only single-layer nano-metal particles distributed in a patterned array are left on the film functional layer.
The present invention may employ a top electrode material commonly used in existing memory devices, in some embodiments, the top electrode layer is a metal of Pt, TiN, W, or Au; preferably, a magnetron sputtering or electron beam evaporation process is used to deposit the upper electrode layer on the substrate with the patterned nano-metal particles on the surface.
In some embodiments, in step (5), the upper electrode layer is deposited on the substrate with the patterned nano-metal particles prepared on the surface by using a magnetron sputtering process, and the process conditions of magnetron sputtering are as follows: the temperature is room temperature and the deposition speed is
Figure BDA0003625099500000081
The deposition time is 1500-2000 s.
In other embodiments, an electron beam evaporation process is used to deposit the upper electrode layer on the substrate with the patterned nano-metal particles on the surface, and the process conditions of the electron beam evaporation are as follows: the temperature is room temperature, the deposition speed is 2.5nm/min, and the deposition time is 20-40 min.
In some embodiments, step (6) applies a positive bias voltage of 1-5V to the upper electrode layer to generate a topological phase change inside the thin film functional layer to form a BM-SXO barrier layer.
The invention also provides a self-forming topological phase change nano memory device structure which comprises SrTiO from bottom to top 3 Substrate, SrRuO 3 A thin film lower electrode layer, a mixed SXO thin film functional layer, a patterned nano metal oxide particle layer and an upper electrode layer; wherein the content of the first and second substances,
the mixed SXO film functional layer is obtained by orderly and crossly distributing nanoscale PV-SXO conductive wires and BM-SXO barrier layers which are vertical to the in-plane direction of the film; the patterned layer of nano-metal oxide particles comprises patterned nano-metal oxide particles; the nanometer metal oxide particles are aligned with the BM-SXO barrier layer in the mixed thin film functional layer, so that the BM-SXO barrier layer can not generate topological phase change switching any more; gaps among the nano metal oxide particles and the mixed thin film functional layerThe PV-SXO conductive filaments in (1) are aligned. Wherein PV-SXO is SrXO m The BM-SXO is SrXO 2.5 (ii) a Wherein X is Fe or Co, and m is more than or equal to 2.85 and less than 3. When the device is used, the oxygen content of PV-SXO in the mixed thin film functional layer is regulated and controlled by changing the direction of an electric field applied between the lower electrode layer and the upper electrode layer of the device, so that the resistance value of the thin film functional layer is regulated and controlled.
Actually, when the polystyrene nanometer microsphere is used as a mask to prepare the device structure, the transverse dimension (transverse direction is parallel to the in-plane direction of the film) of the nanometer-scale BM-SXO barrier layer in the finally formed mixed film functional layer is the diameter of the polystyrene nanometer microsphere, the dimension of the nanometer-scale PV-SXO conductive wire in the mixed film functional layer is the gap dimension between the polystyrene nanometer microsphere and the microsphere, and the dimension of the PV-SXO conductive wire and the dimension of the BM-SXO barrier layer are in an order of magnitude. In practical application, the size of the nanometer PV-SXO conductive wire in the mixed film functional layer can be adjusted by adjusting the diameter of the polystyrene nanometer microsphere, so that the size of the BM-SXO barrier layer can be adjusted.
In some embodiments, the hybrid SXO thin film functional layer has a thickness of 10 to 30 nm. The thickness of the mixed film functional layer needs to ensure that the metal nanoparticles can completely absorb oxygen in the self-aligned film functional layer under the applied positive bias condition of 1-5V and convert the oxygen into metal oxide nanoparticles. Therefore, the thickness is not too thick, the oxidation capability of the metal nanoparticles exceeding 30nm may not be enough to completely absorb O in PV-SXO in the self-aligned thin film functional layer, and the epitaxy of the functional layer thin film exceeding 30nm and the substrate can undergo stress relaxation, so that the ferroelectric polarization capability of the functional layer is influenced by the change of the lattice constant. And the electron tunneling is induced below 10nm, a Schottky emission mechanism is generated besides a conductive wire mechanism, and the uniformity of the device is influenced.
The memory device structure provided by the invention can be used for preparing a memristor or a ferroelectric memory. The nano memory device structure prepared by the invention and taking SFO or SCO as the main body material of the thin film functional layer of the device absorbs part of O ions in SXO by utilizing the property that metal nano particles are easy to be oxidized, and at the moment, the part below the metal nano particlesThe SXO film is in an anoxic state to form a BM-SXO phase blocking layer with higher resistance, at the moment, the size of the PV-SXO conductive wire is determined by the size of the metal nano-particles, and the direction of the PV-SXO conductive wire is limited to be vertical to the in-plane direction of the film to a certain degree. The PV-SFO conductive wire vertical to the film surface direction can realize the switching of the resistance state in the field of memristors by utilizing the topological phase change mechanism of the PV-SFO conductive wire, and can also realize the switching of the PV-SFO conductive wire in the field of memristors by utilizing SrFeO m The application of proper bias voltage to generate ferroelectric polarization expands the application of the device in the field of ferroelectric memories.
The invention discloses a Pt/nano-Metal/SXO/SRO device, which is prepared by growing Al/Fe/Cu/Ti nano-particles on an SXO (X ═ Fe, Co) film, wherein the Al/Fe/Cu/Ti nano-particles are easy to oxidize, the SXO film below the Al/Fe/Cu/Ti nano-particles is in an anoxic state to form a BM-SXO phase barrier layer with higher resistance, the size of a PV-SXO conductive wire is determined by the size of the Al/Fe/Cu/Ti nano-particles, and the direction of the PV-O conductive wire is limited to be vertical to the in-plane direction of the film to a certain extent.
The following are examples:
example 1
(1) Ultrasonic cleaning of SrTiO in acetone and ethanol respectively 3 Substrate for 5 min;
(2) preparing SrRuO on the substrate in the step (1) by using a pulsed laser deposition device 3 The thin film lower electrode layer has the following process conditions: the temperature is 700 ℃, the atmosphere of the cavity is oxygen, the air pressure is 3Pa, the laser energy is 450mJ, the laser frequency is 4Hz, and the vacuum degree is 5 multiplied by 10 -6 Pa, the distance between the substrate and the target material is 55 mm; the deposition time was 3600s, and the resulting cross-sectional and top-view of the substrate is shown in FIG. 1.
(3) Preparing SrFeO on the lower electrode film in the step (2) by using a pulse laser deposition device m (m is more than or equal to 2.85 and less than 3) a film functional layer, and the process conditions are as follows: the temperature is 650 ℃, the atmosphere of the cavity is oxygen, the air pressure is 7Pa, the laser energy is 250mJ, the laser frequency is 4Hz, and the vacuum degree is 5 multiplied by 10 -6 Pa, substrate and target materialThe spacing is 55 mm; the deposition time was 1000s and the resulting cross-sectional and top views of the substrate are shown in FIG. 2.
(4) Firstly dispersing 5g of polystyrene nano-microspheres in 100mL of deionized water, then adding 60mL of ethanol as a dispersing agent, and finally further performing ultrasonic dispersion on the diluted and dispersed polystyrene nano-microspheres to obtain a uniform ethanol-dispersed polystyrene nano-microsphere mixed solution. The slides were inserted into a petri dish at approximately 30 ° slant, and deionized water was placed in the petri dish. Slowly dripping the mixed solution of the polystyrene spheres on an inclined glass slide, uniformly spreading the polystyrene spheres on the surface of deionized water through the drainage of the glass slide, and dripping 2 drops of sodium dodecyl sulfate (aqueous solution of SDS) with the concentration of 3 wt% after the solution is completely spread to further strengthen the surface tension of the polystyrene spheres so as to ensure that a polystyrene sphere film is more compact. After the above steps are completed, the substrate obtained in the step (3) is stretched into the lower part of the polystyrene spherical membrane by using tweezers so that the spherical membrane is transferred to the surface of the substrate. The substrate coated with the polystyrene spherical membrane solution is placed in a clean culture dish, dried at room temperature, and after the solvent is completely volatilized, the self-assembled polystyrene spherical membrane is completely attached to the surface of the substrate, as shown in fig. 3.
(5) Depositing metal Al on the film in the step (4) by using electron beam evaporation equipment, wherein the temperature is room temperature, the growth rate is 0.1nm/s, and the deposition time is 200 s; the resulting cross-sectional and top views of the substrate are shown in fig. 4.
(6) Sequentially placing the substrate obtained in the step (5) in toluene, acetone, isopropanol and deionized water to remove the polystyrene nano microspheres on the surface and remove the redundant metal Al; the resulting cross-sectional and top views of the substrate are shown in fig. 5. The polystyrene nano microspheres laid in the single layer are equivalent to a mask, when metal Al is deposited on the surface of the polystyrene nano microspheres laid in the single layer by adopting an electron beam evaporation process, the metal Al is only deposited between the polystyrene nano microspheres laid in the single layer and the microspheres, and even if excessive metal is deposited, the metal Al can be cleaned along with the polystyrene microspheres during cleaning, and only single-layer nano metal particles distributed in a patterned array are left on the film functional layer.
(7) The substrate obtained in the above step (6) using a magnetron sputtering apparatusDepositing metal Pt on the sheet as an upper electrode layer, wherein the process conditions are as follows: the temperature is room temperature and the deposition speed is
Figure BDA0003625099500000111
The deposition time was 2000 s; the resulting cross-sectional and top views of the substrate are shown in fig. 6.
(8) And (4) applying 3V positive bias on the Pt upper electrode layer obtained in the step (7) to generate topological phase change inside the functional layer to form a BM-SFO barrier layer, wherein a cross section view and a top view of the obtained substrate are shown in FIG. 7.
In this embodiment, Al nanoparticles are grown on an SXO (X ═ Fe) thin film to prepare a Pt/nano-Metal/SXO/SRO device, and a part of O ions in the SXO is absorbed by using the property that the Al nanoparticles are easily oxidized, and the SXO thin film below the Al nanoparticles is in an oxygen-deficient state to form a BM-SXO phase barrier layer with a high resistance, and at this time, the size of the PV-SXO conductive filament is determined by the size of the Al nanoparticles, and the direction of the PV-SXO conductive filament is limited to be perpendicular to the in-plane direction of the thin film to some extent. Fig. 8 and 9 show schematic diagrams of a principle before and after forming a BM-SXO barrier layer of a Pt/nano-Metal/SXO/SRO memristor prepared in example 1, which shows that the device can form a nano-scale BM-SXO barrier layer through oxygen absorption capacity of nano Al particles, and further form a PV-SXO conductive wire structure with a consistent direction, so that consistency and reliability of the device are effectively improved, and application of a topological phase change material SXO in the field of memristors or ferroelectric memories is promoted. In FIG. 9, dark spheres represent oxygen octahedrons, light spheres represent oxygen tetrahedrons, and the BM-SFO conductive filaments located right under the alumina nanoparticles are formed by overlapping octahedrons and tetrahedrons.
Example 2
(1) Ultrasonic cleaning of SrTiO in acetone and ethanol respectively 3 Substrate for 5 min;
(2) preparing SrRuO on the substrate in the step (1) by using a pulsed laser deposition device 3 The thin film lower electrode layer has the following process conditions: the temperature is 700 ℃, the atmosphere of the cavity is oxygen, the air pressure is 3Pa, the laser energy is 450mJ, the laser frequency is 4Hz, and the vacuum degree is 5 multiplied by 10 -6 Pa, the distance between the substrate and the target material is 55mm, and the deposition time is 3600 s;
(3) preparing SrCoO on the lower electrode film in the step (2) by using a pulse laser deposition device m The functional thin film layer has the following process conditions: the temperature is 650 ℃, the atmosphere of the cavity is oxygen, the air pressure is 7Pa, the laser energy is 250mJ, the laser frequency is 4Hz, and the vacuum degree is 5 multiplied by 10 -6 Pa, the distance between the substrate and the target material is 55 mm; the deposition time was 1000 s.
(4) Firstly dispersing 5g of polystyrene nano-microspheres in 100mL of deionized water, then adding 60mL of ethanol as a dispersing agent, and finally further performing ultrasonic dispersion on the diluted and dispersed polystyrene nano-microspheres to obtain a uniform ethanol-dispersed polystyrene nano-microsphere mixed solution. The slides were inserted into a petri dish at approximately 30 ° slant, and deionized water was placed in the petri dish. Slowly dripping the mixed solution of the polystyrene spheres on an inclined glass slide, uniformly spreading the polystyrene spheres on the surface of deionized water by guiding the polystyrene spheres through the glass slide, and dripping Sodium Dodecyl Sulfate (SDS) with the concentration of 3 wt% after the solution is completely spread to further enhance the surface tension of the polystyrene spheres so that a polystyrene sphere membrane is more compact. After the above steps are completed, the substrate obtained in the step (3) is stretched into the lower part of the polystyrene spherical membrane by using tweezers so that the spherical membrane is transferred to the surface of the substrate. And (3) placing the substrate coated with the polystyrene spherical membrane solution in a clean culture dish, drying at room temperature, and completely attaching the self-assembled polystyrene spherical membrane on the surface of the substrate after the solvent is completely volatilized.
(5) And (4) depositing metal Al on the film in the step (4) by using an electron beam evaporation device, wherein the temperature is room temperature, the growth rate is 0.1nm/s, and the deposition time is 200 s.
(6) Sequentially placing the substrate obtained in the step (5) in toluene, acetone, isopropanol and deionized water to remove the polystyrene nano microspheres on the surface and redundant metal Al;
(7) and (3) depositing metal Pt on the substrate obtained in the step (6) by using a magnetron sputtering device as an upper electrode layer under the following process conditions: the temperature is room temperature, the deposition speed is
Figure BDA0003625099500000131
The deposition time was 2000 s;
(8) and (4) applying a positive bias voltage of 3V on the Pt upper electrode layer obtained in the step (7) to generate topological phase change inside the functional layer to form a BM-SCO barrier layer.
It will be understood by those skilled in the art that the foregoing is only a preferred embodiment of the present invention, and is not intended to limit the invention, and that any modification, equivalent replacement, or improvement made within the spirit and principle of the present invention should be included in the scope of the present invention.

Claims (10)

1. A preparation method of a self-forming topological phase change nano memory device structure is characterized by comprising the following steps:
(1) preparing a thin film lower electrode layer on a substrate;
(2) preparing SrXO on the thin film lower electrode layer m The film functional layer, wherein X is Fe or Co, and m is more than or equal to 2.85 and less than 3;
(3) transferring the polystyrene nano microsphere mixed solution dispersed by the solvent to the surface of the film functional layer, standing to volatilize the solvent, and obtaining the film functional layer paved with single-layer polystyrene nano microspheres;
(4) depositing an active metal layer on the thin film functional layer paved with the single-layer polystyrene nano microspheres; then cleaning the obtained substrate, and removing the polystyrene nano microspheres and redundant metal on the surface of the substrate to obtain the substrate with the patterned nano metal particles on the surface;
(5) depositing an upper electrode layer on the substrate prepared with the patterned nano-metal particles;
(6) and applying positive bias on the upper electrode layer to enable topological phase change to be generated inside the thin film functional layer to form a BM-SXO barrier layer.
2. The method according to claim 1, wherein the lower electrode layer of step (1) is SrRuO 3 Thin film bottom electrode layer, preparation of SrRuO on substrate using pulsed laser deposition process 3 The specific deposition process conditions of the film lower electrode layer are as follows: the temperature is 650-750 ℃, and the atmosphere of the cavity isOxygen gas pressure of 10-15 Pa, laser energy of 250-450 mJ, laser frequency of 1-8 Hz, vacuum degree of 1 × 10 -6 ～1×10 -5 Pa, the distance between the substrate and the target is 40-60 mm.
3. The method of claim 1, wherein step (3) prepares SrXO on the thin film lower electrode layer using a pulsed laser deposition process m The specific deposition process conditions of the thin film functional layer are as follows: the temperature is 650-700 ℃, the atmosphere of the cavity is oxygen, the air pressure is 5-10 Pa, the laser energy is 250-450 mJ, the laser frequency is 1-8 Hz, and the vacuum degree is 1 multiplied by 10 -6 ～1×10 -5 Pa, the distance between the substrate and the target material is 40-60 mm, and the deposition time is 600-1800 s.
4. The preparation method according to claim 1, wherein the solvent in the step (3) is an aqueous solution of ethanol, and the mass ratio of the polystyrene nanospheres, ethanol and water in the solvent-dispersed polystyrene nanosphere mixture is 1: (15-25): (10-15).
5. The method according to claim 4, wherein a surfactant is added to the solvent-dispersed polystyrene nanosphere mixture to increase the surface tension of the polystyrene nanospheres, thereby increasing the degree of density of a spherical film formed by aggregation of the polystyrene nanospheres; then placing the substrate obtained in the step (2) below the spherical membrane, so that the spherical membrane is transferred to the surface of the substrate; and standing to volatilize the solvent to obtain the thin film functional layer paved with the single-layer polystyrene nano microspheres.
6. The method according to claim 1, wherein the active metal in the step (4) is Al, Fe, Ti or Cu; depositing an active metal layer on the thin film functional layer paved with the single-layer polystyrene nano microspheres by an electron beam evaporation process; the specific process conditions are as follows: the temperature is room temperature, the growth rate is 0.08-0.15nm/s, and the deposition time is 180-220 s.
7. The preparation method according to claim 1, wherein in the step (6), a positive bias of 1-5V is applied to the upper electrode layer, so that topological phase change is generated inside the thin film functional layer to form the BM-SXO barrier layer.
8. A self-forming topological phase change nano memory device structure is characterized by comprising SrTiO from bottom to top 3 Substrate, SrRuO 3 A thin film lower electrode layer, a mixed SXO thin film functional layer, a patterned nano metal oxide particle layer and an upper electrode layer; wherein the content of the first and second substances,
the mixed SXO film functional layer comprises ordered and staggered nanoscale PV-SXO conductive wires and a BM-SXO barrier layer, wherein the nanoscale PV-SXO conductive wires are vertical to the in-plane direction of the film; the patterned layer of nano-metal oxide particles comprises patterned nano-metal oxide particles; the nano metal oxide particles are aligned with the BM-SXO barrier layer in the mixed thin film functional layer; gaps among the nano metal oxide particles are aligned with the PV-SXO conductive wires in the mixed thin film functional layer;
wherein PV-SXO is SrXO m The BM-SXO is SrXO 2.5 (ii) a Wherein X is Fe or Co, and m is more than or equal to 2.85 and less than 3;
when the device is used, the oxygen content of PV-SXO in the mixed thin film functional layer is regulated and controlled by changing the direction of an electric field applied between the lower electrode layer and the upper electrode layer of the device, so that the resistance value of the thin film functional layer is regulated and controlled.
9. The memory device structure of claim 8, wherein the hybrid SXO thin film functional layer has a thickness of 10nm to 30 nm.
10. Use of the memory device structure according to claim 8 or 9 for the preparation of memristors or ferroelectric memories.
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* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN117529222A (en) * 2023-12-29 2024-02-06 华中科技大学 Topological phase change memristor with controllable conductive wire forming area and preparation method thereof
CN117529222B (en) * 2023-12-29 2024-03-22 华中科技大学 Topological phase change memristor with controllable conductive wire forming area and preparation method thereof

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