Non-volatile feooh / tio2 heterojunction memristor and preparation and multi-value storage control method thereof

Abstract

The application belongs to the technical field of microelectronic devices, and particularly relates to a nonvolatile FeOOH / TiO2 heterojunction memristor and a preparation and multi-value storage control method thereof. The nonvolatile FeOOH / TiO2 heterojunction memristor comprises a bottom electrode, a TiO2 resistive switching layer and a FeOOH resistive switching layer which are epitaxially grown on the bottom electrode in sequence, and an upper electrode deposited on the surface of the FeOOH resistive switching layer. The preparation method comprises the following steps: placing a bottom electrode substrate with a conductive surface downward in a water heating reaction kettle inner container, adding a reaction solution prepared by tetrabutyl titanate, keeping part of the bottom electrode substrate higher than the reaction solution surface, sealing, and placing in a muffle furnace for water heating reaction; obtaining a TiO2 / bottom electrode sample; placing an epitaxial growth surface downward in the water heating reaction kettle inner container, adding a reaction solution of FeCl3.6H2O, sealing, and placing in a muffle furnace for water heating reaction to obtain a required FeOOH / TiO2 / bottom electrode heterojunction sample; and depositing an upper electrode with a certain thickness and morphology on the surface. The application provides a low-cost and high-density nonvolatile FeOOH / TiO2 heterojunction memristor.

Description

Technical Field

[0001] This invention belongs to the field of microelectronic device technology, specifically relating to a non-volatile FeOOH / TiO2 heterojunction memristor, its preparation, and a method for multi-value storage control. Background Technology

[0002] As the fourth basic circuit element after resistors, inductors, and capacitors, memristors not only have advantages such as simple structure, high storage density, fast storage speed, low power consumption, multi-value storage, and three-dimensional storage, but also have a huge advantage in miniaturization. They are considered one of the strong contenders for the next generation of non-volatile memory.

[0003] Transition metal oxide TiO2 has attracted close attention from researchers due to its simple preparation process, low cost, stable chemical properties, corrosion resistance, high photoelectric conversion efficiency, and excellent resistive switching memory performance. However, how to achieve controllable design of low-cost, high-density multi-value storage performance of TiO2 memristors remains an urgent problem to be solved.

[0004] Patent CN 110137351 B discloses "A Nitrogen-Doped Titanium Dioxide Array Memristor and Its Fabrication Method," which uses urea and ammonium salts as nitrogen sources to fabricate a nitrogen-doped titanium dioxide array memristor through hydrothermal synthesis and vacuum evaporation. The resistive switching layer of this device has a nitrogen-to-titanium ratio of 0.5% to 15% in nitrogen-doped rutile TiO2, and its fabrication process is relatively complex, which is detrimental to cost control and commercial application. Furthermore, the resistive switching performance of this device is relatively low, only reaching one order of magnitude, resulting in low reliability. Simultaneously, this device does not achieve the design of a heterojunction structure or the controllability of high-density multi-value storage. Therefore, designing a low-cost, high-density non-volatile FeOOH / TiO2 heterojunction memristor and achieving controllable modulation of the device's multi-value storage performance is of significant research importance for the application of next-generation non-volatile high-density memories. Summary of the Invention

[0005] To address the shortcomings of existing technologies, the present invention aims to provide a non-volatile FeOOH / TiO2 heterojunction memristor, its fabrication, and a method for controlling multi-value storage. This device employs an optimized FeOOH / TiO2 shell-core structure n-type heterojunction and achieves precise control of high-density multi-value storage by orderly modulating the bias voltage. It has significant application prospects in next-generation non-volatile high-density memories.

[0006] The specific objectives of this invention are as follows:

[0007] 1. Design a low-cost, high-density non-volatile FeOOH / TiO2 core-shell structure n-type heterojunction memristor.

[0008] 2. To achieve the design of devices with non-volatility, high stability, high reliability, and high resistance-to-switching ratio.

[0009] 3. Achieve controllable design for high-density multi-value storage of devices.

[0010] Specific technical solutions:

[0011] A non-volatile FeOOH / TiO2 heterojunction memristor includes a bottom electrode on which a TiO2 resistive switching layer and a FeOOH resistive switching layer are epitaxially grown sequentially. A top electrode is deposited on the surface of the FeOOH resistive switching layer. The resistive switching layer is fabricated using a simple, inexpensive, and efficient hydrothermal method, while the top electrode is designed using magnetron sputtering deposition technology. As an optimized design for the device structure, the TiO2 nanorods in the resistive switching layer have a diameter of approximately 80 nm and a length of approximately 450 nm. Multi-valued storage control of this device is achieved through ordered modulation of an applied bias voltage, current restriction, or excitation by an applied optical field or magnetic field.

[0012] The fabrication method of a non-volatile FeOOH / TiO2 heterojunction memristor includes the following steps:

[0013] Step 1, Preparation of the TiO2 / bottom electrode sample reaction solution. First, the tetrabutyl titanate reaction solution is prepared under magnetic stirring. The volume ratio of deionized water to hydrochloric acid in the reaction solution is 1:1, and the volume ratio of tetrabutyl titanate to the reaction solution is 1 / 60 to 1 / 12.

[0014] Besides FTO, other electrodes can be used for the bottom electrode, such as metal Ti sheets or other electrodes suitable for hydrothermal growth.

[0015] Step 2: Place a clean bottom electrode substrate with a size of 3cm×4cm and the conductive side facing down obliquely in the inner liner of a 100mL volume hydrothermal reactor. Add the reaction solution from Step 1 in proportion, while keeping part of the bottom electrode substrate above the reaction solution surface. After sealing, place it in a muffle furnace. The hydrothermal reaction temperature is 110~160℃ and the time is 3~7h.

[0016] Step 3: After the hydrothermal reaction is completed, cool the reactor from Step 2 to room temperature, remove the inner liner of the reactor, take out the bottom electrode sample and rinse it with ethanol and deionized water in sequence, and let it air dry to obtain the desired TiO2 / bottom electrode sample.

[0017] Step 4: Preparation of the reaction solution for the FeOOH / TiO2 / bottom electrode heterojunction sample. A reaction solution containing FeCl3·6H2O was prepared under magnetic stirring. The concentration of FeCl3·6H2O was 0.03–0.33 mol / L.

[0018] Step 5: Place the TiO2 / bottom electrode sample prepared in Step 3 with the epitaxial growth surface facing down in the inner liner of a 100mL hydrothermal reactor. Add the reaction solution from Step 4 in proportion, keeping the volume of the added reaction solution consistent with that added in Step 2. After sealing, place it in a muffle furnace. The hydrothermal reaction temperature is 80-150℃, and the time is 3-12h.

[0019] Step 6: After the hydrothermal reaction is completed, cool the reactor from Step 5 to room temperature, remove the inner liner of the reactor, take out the sample and rinse it with deionized water, and let it air dry to obtain the desired FeOOH / TiO2 / bottom electrode heterojunction sample.

[0020] Step 7: Deposit a top electrode of a certain thickness and morphology on the surface of the FeOOH / TiO2 / bottom electrode heterojunction sample prepared in Step 6 to realize the fabrication of the FeOOH / TiO2 heterojunction memristor. The top electrode of the device can be either a metal electrode or a non-metal electrode.

[0021] For the FeOOH / TiO2 heterojunction resistive switching layer of the device, it can also be prepared by techniques such as magnetron sputtering deposition, plasma-enhanced atomic layer deposition, chemical vapor deposition, electron beam evaporation deposition, sol-gel method, and anodic oxidation method.

[0022] Besides magnetron sputtering deposition, other methods can be used to fabricate the top electrode, such as thermal evaporation, chemical vapor deposition, and molecular beam epitaxy. Furthermore, in addition to using the W top electrode, other metallic or non-metallic electrodes can be selected to replace it, such as those made of Au, Pt, Ag, Cu, Ni, Co, Al, Ti, TaN, TiN, C, and graphene.

[0023] The multi-value storage control method of the device achieves controllable modulation of the device's multi-value storage by orderly modulating an applied bias voltage, limiting current, or applying an external optical field or magnetic field excitation. The electrical performance of the device was analyzed using an Agilent B2901A instrument.

[0024] The beneficial effects of this invention are as follows:

[0025] 1. This invention provides a low-cost, high-density non-volatile FeOOH / TiO2 heterojunction memristor.

[0026] 2. This invention provides a simple, inexpensive, and efficient hydrothermal preparation process, realizing the controllable design of FeOOH / TiO2 heterojunctions, and providing a simple and efficient process for the development and application of related materials.

[0027] 3. The FeOOH / TiO2 heterojunction memristor provided by this invention has high stability, high reliability, high resistance-to-switching ratio, and non-volatile bipolar resistance-to-switching memory characteristics, providing a new fabrication method for the application of next-generation non-volatile memory.

[0028] 4. The FeOOH / TiO2 heterojunction memristor provided by this invention has high-density multi-value storage characteristics with controllable bias voltage, and has important application prospects in the next generation of non-volatile high-density memory. Attached Figure Description

[0029] Figure 1 This is a schematic diagram of the device obtained in Embodiment 1 of the present invention;

[0030] Figure 2 The image shows the surface morphology of the TiO2 / FTO sample prepared in Example 1 of this invention using FESEM.

[0031] Figure 3 The image shows the surface morphology of the FeOOH / TiO2 / FTO heterojunction sample prepared in Example 1 of this invention via FESEM.

[0032] Figure 4 The image shows the cross-sectional morphology FESEM image of the FeOOH / TiO2 / FTO heterojunction sample prepared in Example 1 of this invention.

[0033] Figure 5 XPS image and Gaussian fine fitting image of Fe2p on the surface of the FeOOH / TiO2 / FTO heterojunction sample prepared in Example 1 of this invention;

[0034] Figure 6 XPS image and Gaussian fine fitting image of O1s on the surface of the FeOOH / TiO2 / FTO heterojunction sample prepared in Example 1 of this invention;

[0035] Figure 7 This is a semi-logarithmic IV curve of the device designed in Embodiment 2 of the present invention under 50 cycles of voltage scanning;

[0036] Figure 8 This is a semi-logarithmic IV curve of the device designed in Embodiment 2 of the present invention under reverse bias voltage regulation. Detailed Implementation

[0037] The present invention will now be described in detail with reference to the accompanying drawings.

[0038] Example 1

[0039] Fabrication of a nonvolatile FeOOH / TiO2 heterojunction memristor

[0040] The non-volatile FeOOH / TiO2 heterojunction memristor prepared in this embodiment has the following structure: Figure 1 As shown, it includes a bottom electrode 1, on which a TiO2 resistive switching layer 2 and a FeOOH resistive switching layer 3 are epitaxially grown sequentially, and an upper electrode 4 is deposited on the surface of the FeOOH resistive switching layer 3.

[0041] The upper electrode 4 of the device is a metal W electrode (with a thickness of about 80 nm), the TiO2 resistive switching layer 2 and the FeOOH resistive switching layer 3 are FeOOH / TiO2 shell-core structure n-type heterojunction structures (with a thickness of about 450 nm), and the bottom electrode 1 is an FTO substrate.

[0042] The specific steps for fabricating a non-volatile FeOOH / TiO2 heterojunction memristor are as follows:

[0043] Step 1, Preparation of TiO2 / FTO sample reaction solution. First, a reaction solution containing a certain proportion of tetrabutyl titanate was prepared under magnetic stirring. The volume ratio of deionized water to hydrochloric acid in the reaction solution was 1:1, and the volume ratio of tetrabutyl titanate to the reaction solution was 1 / 60.

[0044] Step 2: Place a clean FTO substrate with a size of 3cm×4cm and the conductive side facing down obliquely in the inner liner of a 100mL volume hydrothermal reactor, add 25mL of the reaction solution from Step 1 according to the ratio, seal it and place it in a muffle furnace, the hydrothermal reaction temperature is 150℃ and the time is 4h.

[0045] Step 3: After the hydrothermal reaction is complete, cool the reaction vessel from Step 2 to room temperature, remove the inner liner of the reaction vessel, take out the FTO sample and rinse it with ethanol and deionized water in sequence, then let it air dry to obtain the desired TiO2 / FTO sample. The diameter of the prepared TiO2 nanorod sample is approximately 80 nm. Figure 2 As shown.

[0046] Step 4: Preparation of the reaction solution for the FeOOH / TiO2 / FTO heterojunction sample. A reaction solution containing a certain concentration of FeCl3·6H2O was prepared under magnetic stirring. The concentration of FeCl3·6H2O was 0.33 mol / L.

[0047] Step 5: Place the TiO2 / FTO sample prepared in Step 3 with the epitaxial growth surface facing down in the inner liner of a 100mL hydrothermal reactor, add 25mL of the reaction solution from Step 4 according to the ratio, seal it, and place it in a muffle furnace. The hydrothermal reaction temperature is 100℃ and the time is 6h.

[0048] Step 6: After the hydrothermal reaction is complete, cool the reactor from Step 5 to room temperature, remove the inner liner of the reactor, take out the sample and rinse it with deionized water, then air dry it to obtain the desired FeOOH / TiO2 / FTO heterojunction sample with a thickness of approximately 450 nm. Figure 3 and Figure 4 As shown.

[0049] like Figure 5 As shown, Fe 2p can be observed near the binding energies of 724.56 eV and 712.19 eV, respectively. 1 / 2 and Fe 2p 3 / 2 Peaks. Furthermore, FeOOH was also observed near the binding energies of 717.72 eV and 732.81 eV. 3+ Corresponding satellite peaks.

[0050] like Figure 6 As shown, there is a certain concentration of oxygen vacancy defects on the sample surface. The presence of oxygen vacancy defects on the sample surface can serve as carrier trapping centers, which will directly affect the resistive switching performance of the device.

[0051] Step 7: Using a metal mask magnetron sputtering deposition technique, a metal top electrode of a certain thickness and morphology is sputtered and deposited on the surface of the FeOOH / TiO2 / FTO heterojunction sample prepared in Step 6, thereby realizing the fabrication of the FeOOH / TiO2 heterojunction memristor. The top electrode of the device is a metal W electrode with a thickness of 80 nm and a diameter of 10 μm. The process conditions for the metal mask magnetron sputtering deposition technique are: argon atmosphere, background vacuum of 6 × 10⁻⁶. -5 Pa, working pressure is 0.5 Pa, DC sputtering power is 100 W, and time is 1000 s.

[0052] Example 2

[0053] A method for controlling the multi-value storage of a non-volatile FeOOH / TiO2 heterojunction memristor is proposed, which adopts the form of orderly control of the reverse bias voltage to achieve controllable modulation of the multi-value storage of the device.

[0054] The specific steps for controlling the multi-value storage of the device are as follows:

[0055] 1. First, since the device does not require an electroforming activation process, a bias voltage is directly applied to the upper electrode W of the device under a current limit of 0.1A to test and adjust the resistive switching performance of the device, while keeping the bottom electrode of the device grounded during the testing and adjustment process.

[0056] 2. Secondly, regarding device performance testing. For example... Figure 7As shown, under 50 voltage scan cycles, the device exhibits high stability, high reliability, and non-volatile bipolar resistive switching characteristics. The set voltage and reset voltage of the device can be stably maintained around -2.22V and 1.56V, respectively. In addition, the resistive switching ratio of the device can be stably maintained at 0.1V for more than two orders of magnitude, demonstrating excellent non-volatile resistive storage characteristics.

[0057] 3. Finally, regarding the multi-value storage control of devices. For example... Figure 8 As shown, the forward bias voltage of the fixed device is 4V, and the reverse bias voltage of the device is controlled in an orderly manner from -2V, -2.5V to -3V, realizing the controllable modulation of the device in low-resistivity and high-resistivity multi-value storage.

[0058] To clarify, the above embodiments are merely device fabrication and multi-value storage control techniques under optimized process conditions and control methods. Any aspects involving the structure and fabrication process of the FeOOH / TiO2 / FTO heterojunction resistive switching layer of this device, the fabrication of the upper or lower electrode and the equivalent electrode replacement fabrication, and multi-value storage control methods under applied bias voltage, current limiting, and other physical field excitations, all fall within the design scope of this patent.

Claims

1. A non-volatile FeOOH / TiO2 heterojunction memristor, characterized in that, The electrode includes a bottom electrode, on which a TiO2 resistive switching layer and a FeOOH resistive switching layer are epitaxially grown sequentially. An upper electrode is deposited on the surface of the FeOOH resistive switching layer. The upper electrode is a W metal electrode, and the bottom electrode is an FTO substrate. Obtained by the following preparation method: Step 1, Preparation of TiO2 / bottom electrode sample reaction solution: Prepare the tetrabutyl titanate reaction solution under magnetic stirring; Step 2: Place the clean bottom electrode substrate with the conductive side facing down obliquely inside the hydrothermal reactor, add the reaction solution from Step 1 in proportion, while keeping part of the bottom electrode substrate above the reaction solution surface, seal and place in a muffle furnace for hydrothermal reaction. Step 3: After the hydrothermal reaction is completed, cool to room temperature, take out the bottom electrode sample and rinse it with ethanol and deionized water in sequence, and let it air dry to obtain the desired TiO2 / bottom electrode sample. Step 4, Preparation of reaction solution for FeOOH / TiO2 / bottom electrode heterojunction sample: Prepare a reaction solution containing FeCl3▪6H2O under magnetic stirring; Step 5: Place the TiO2 / bottom electrode sample prepared in Step 3 with the epitaxial growth surface facing down in the inner liner of the hydrothermal reactor, add the reaction solution from Step 4 in proportion, keeping the volume of the added reaction solution consistent with that of the reaction liquid added in Step 2, seal it and place it in a muffle furnace. Step 6: After the hydrothermal reaction is completed, the reactor is cooled to room temperature, the sample is taken out and rinsed with deionized water, and then air-dried to obtain the desired FeOOH / TiO2 / bottom electrode heterojunction sample. Step 7: Deposit a top electrode of a certain thickness and morphology on the surface of the FeOOH / TiO2 / bottom electrode heterojunction sample prepared in Step 6 to realize the fabrication of the FeOOH / TiO2 heterojunction memristor.

2. The method for preparing the non-volatile FeOOH / TiO2 heterojunction memristor according to claim 1, characterized in that, Includes the following steps: Step 1, Preparation of TiO2 / bottom electrode sample reaction solution: Prepare the tetrabutyl titanate reaction solution under magnetic stirring; Step 2: Place the clean bottom electrode substrate with the conductive side facing down obliquely inside the hydrothermal reactor, add the reaction solution from Step 1 in proportion, while keeping part of the bottom electrode substrate above the reaction solution surface, seal and place in a muffle furnace for hydrothermal reaction. Step 3: After the hydrothermal reaction is completed, cool to room temperature, take out the bottom electrode sample and rinse it with ethanol and deionized water in sequence, and let it air dry to obtain the desired TiO2 / bottom electrode sample. Step 4, Preparation of reaction solution for FeOOH / TiO2 / bottom electrode heterojunction sample: Prepare a reaction solution containing FeCl3▪6H2O under magnetic stirring; Step 5: Place the TiO2 / bottom electrode sample prepared in Step 3 with the epitaxial growth surface facing down in the inner liner of the hydrothermal reactor, add the reaction solution from Step 4 in proportion, keeping the volume of the added reaction solution consistent with that of the reaction liquid added in Step 2, seal it and place it in a muffle furnace. Step 6: After the hydrothermal reaction is completed, the reactor is cooled to room temperature, the sample is taken out and rinsed with deionized water, and then air-dried to obtain the desired FeOOH / TiO2 / bottom electrode heterojunction sample. Step 7: Deposit a top electrode of a certain thickness and morphology on the surface of the FeOOH / TiO2 / bottom electrode heterojunction sample prepared in Step 6 to realize the fabrication of the FeOOH / TiO2 heterojunction memristor.

3. The method for preparing the non-volatile FeOOH / TiO2 heterojunction memristor according to claim 2, characterized in that, In step 1, the volume ratio of deionized water to hydrochloric acid in the reaction solution is 1:1, and the volume ratio of tetrabutyl titanate to the reaction solution is 1 / 60 to 1 / 12.

4. The method for preparing the non-volatile FeOOH / TiO2 heterojunction memristor according to claim 2, characterized in that, In step 2, the hydrothermal reaction temperature is 110~160℃ and the time is 3~7h.

5. The method for preparing the non-volatile FeOOH / TiO2 heterojunction memristor according to claim 2, characterized in that, In step 4, the concentration of FeCl3▪6H2O is 0.03~0.33 mol / L.

6. The method for preparing the non-volatile FeOOH / TiO2 heterojunction memristor according to claim 2, characterized in that, In step 5, the hydrothermal reaction temperature is 80~150℃ and the time is 3~12h.

7. The multi-value storage control method for a non-volatile FeOOH / TiO2 heterojunction memristor according to claim 1, characterized in that, Controllable modulation of multi-value storage in devices can be achieved by orderly modulating an applied bias voltage, limiting current, or applying an external optical field or magnetic field excitation.

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