Perovskite composite thin film memristor and preparation method thereof

Abstract

The application provides a perovskite composite thin film memristor and a preparation method thereof. The memristor is formed with an ITO bottom electrode, a composite resistive switching layer and a TiN top electrode on a glass substrate in sequence; the composite resistive switching layer is composed of a lower layer of molybdenum oxide and an upper layer of methylamine lead iodine. The preparation method comprises the following steps: cleaning and drying the glass substrate; sputtering ITO on the glass substrate by a radio frequency magnetron sputtering method to form the ITO bottom electrode; growing molybdenum oxide on the ITO bottom electrode by a magnetron sputtering method and growing methylamine lead iodine by a sol-gel method and a post annealing process; and growing the TiN top electrode on the methylamine lead iodine thin film. The memristor provided by the application uses molybdenum oxide and methylamine lead iodine as the composite resistive switching layer, has good performance, and is a memory with more stable storage performance, strong durability and wider application prospect.

Description

Technical Field

[0001] This invention relates to the field of memory technology, specifically to a perovskite composite thin-film memristor and its fabrication method. Background Technology

[0002] In recent years, traditional non-volatile memory devices have approached their physical limits, and the development of next-generation non-volatile memories has become a hot research area for scientists worldwide. Currently, the main types of non-volatile memories include magnetic memory, magnetic memory, phase-change memory, and resistive random access memory (RRAM). Among them, RRAM is widely considered a strong contender for next-generation non-volatile memory due to its advantages such as simple structure, fast operation speed, good scalability, good robustness, low power consumption, fast read / write speed, good data retention, simple fabrication, and ease of integration. It is a promising next-generation memory with significant application potential.

[0003] The earliest observed resistive switching effect dates back to 1962, and subsequently, more materials were confirmed to possess resistive switching properties. In 2002, Zhuang et al. first fabricated a 64-bit resistive switching memory array using complementary metal-oxide-semiconductor (CMOS) technology. In 2005, Baek et al. successfully demonstrated a binary transition metal-oxide-semiconductor (BMOS) resistive switching memory, which sparked extensive research on resistive switching memories. After 2008, resistive switching memories were also known as memristors, considered the fourth type of basic passive circuit element besides resistors, capacitors, and inductors, and have been applied to emerging fields such as artificial synapses and logic operations. The general structure of a memristor is a typical sandwich structure, with upper and lower electrodes and a variable resistive material placed between the upper and lower electrodes that can generate resistive switching. Under the action of an applied bias voltage, the resistance state of the device will change from high to low resistance, thereby realizing the storage of 0 and 1. For memristors, the choice of different resistive switching layer materials has a significant impact on the device; it can be said that the resistive switching layer material is the core of the memristor.

[0004] Scientific research shows that there are many types of materials that can be used as resistive switching layers, currently mainly falling into four categories. First, transition metal oxides. Transition metal binary oxides have advantages such as simple composition, low cost, ease of preparation, and compatibility with CMOS processes. Second, solid electrolytes. These memristors typically have a sandwich structure, including an electrochemically active electrode (Ag, Cu, etc.), an electrochemically inert electrode (W, Pt, etc.), and a resistive switching layer composed of a solid electrolyte material. Their resistive switching characteristics are due to the formation and breakage of metal conductive filaments caused by the migration of metal cations generated by the electrochemical reaction of the active metal electrode material under the influence of an electric field. Third, organic materials. Currently, organic materials are simple to prepare and inexpensive, and research on using the bistable characteristics of organic materials to fabricate memristors is widespread. The biggest advantage of organic materials is their wide variety, offering a large selection. Finally, perovskite oxides. Perovskite materials are easy to prepare, have long carrier diffusion lengths, low binding energies, excellent electrical properties, and processing performance, making them very suitable for use as resistive switching layer materials in memristors. Summary of the Invention

[0005] The purpose of this invention is to provide a perovskite composite thin-film memristor and its preparation method. By combining perovskite methylamine lead iodine with molybdenum oxide to form a composite resistive switching layer, a new high-performance non-volatile memristor with stable resistance changes, good storage performance, good memory characteristics, good fatigue resistance and durability, and fast read, write and erase operation speeds is formed.

[0006] This invention is implemented as follows:

[0007] A perovskite composite thin-film memristor has a structure comprising, from bottom to top: a glass substrate, an ITO bottom electrode, a composite resistive switching layer, and a TiN top electrode; wherein the composite resistive switching layer is composed of a lower molybdenum oxide layer and an upper methylamine lead iodide layer, with the molybdenum oxide layer located on the ITO bottom electrode and the methylamine lead iodide layer located on the molybdenum oxide layer.

[0008] In the above scheme, the thickness of the ITO bottom electrode is about 80 nm, and the sputtering time is about 60 min.

[0009] In the above scheme, the thickness of the TiN top electrode is 40 nm, and the sputtering time is about 60 min. The TiN top electrode includes several circular electrodes uniformly distributed on the composite resistive switching layer.

[0010] In the above scheme, the thickness of the composite resistive switching layer is 120 nm, the thickness of the molybdenum oxide layer is 40 nm, and the thickness of the methylamine lead iodine layer is 80 nm.

[0011] This invention also discloses a method for preparing a perovskite composite thin-film memristor, comprising the following steps:

[0012] (1) Pretreatment of the glass substrate;

[0013] (2) ITO bottom electrode was prepared on a glass substrate by magnetron sputtering;

[0014] (3) A molybdenum oxide layer was prepared on the ITO bottom electrode by radio frequency magnetron sputtering; a methylamine lead iodide layer was prepared on the molybdenum oxide layer by sol-gel method; the molybdenum oxide layer and the methylamine lead iodide layer were combined to form a composite resistive switching layer.

[0015] (4) Prepare TiN top electrode on composite resistive switching layer.

[0016] In the above scheme, step (1) specifically involves: first immersing the glass substrate in acetone solution for ultrasonic cleaning for 10 minutes to remove surface stains, then immersing it in alcohol solution for ultrasonic cleaning for 10 minutes, and finally drying it with high-purity nitrogen gas for later use.

[0017] In the above scheme, step (2) specifically involves: placing the glass substrate into the magnetron sputtering vacuum chamber, evacuating the vacuum chamber, injecting argon gas, pre-sputtering for 10 minutes, and then formally sputtering for 60 minutes to form an ITO bottom electrode with a thickness of 80 nm.

[0018] In the above scheme, step (3) of preparing a molybdenum oxide layer on the ITO bottom electrode by magnetron sputtering is as follows: the glass substrate is placed in the magnetron sputtering vacuum chamber, a vacuum is drawn, and argon gas is injected. Then, pre-sputtering is performed for 10 minutes, followed by formal sputtering for 60 minutes, to form a molybdenum oxide layer with a thickness of 40 nm on the ITO bottom electrode.

[0019] In the above scheme, step (3) of preparing the methylamine lead iodine layer on the molybdenum oxide layer using the sol-gel method is as follows: prepare the methylamine lead iodine precursor solution, place the glass substrate with the molybdenum oxide layer on the spin coater, set the spin coating time to 42s and the rotation speed to 4000 rpm, and after stopping the rotation, place the glass substrate on the heating stage to dry, forming a methylamine lead iodine layer with a thickness of 80nm.

[0020] In the above scheme, in step (4), before preparing the TiN top electrode, a mask is first placed on the glass substrate, and circular holes with a diameter of 50 μm are evenly distributed on the mask; the glass substrate is placed in the magnetron sputtering vacuum chamber, a vacuum is drawn, and argon gas is injected. The AC source power is adjusted to make the target material glow, pre-sputter for 4 to 6 minutes, and then formally sputter for 60 minutes to form a TiN top electrode with a thickness of 40 nm.

[0021] The memristor provided by this invention first forms an ITO bottom electrode on a glass substrate by magnetron sputtering, then grows a composite resistive switching layer of molybdenum oxide and perovskite (methylamine lead iodide) on the ITO bottom electrode by magnetron sputtering and sol-gel method, and finally grows a TiN top electrode on the composite resistive switching layer by magnetron sputtering.

[0022] The fabrication method provided by this invention is simple, easy to implement, and highly operable. Performance testing of the fabricated memristor demonstrates its excellent resistive switching characteristics, exhibiting a relatively stable resistance change. Electrical testing reveals a small current, achieving low power consumption. Furthermore, this memristor exhibits superior fatigue resistance in both high and low resistance states. Attached Figure Description

[0023] Figure 1 This is a schematic diagram of the memristor structure in Embodiment 1 of the present invention.

[0024] Figure 2 This is a SEM image of the composite resistive switching layer of the memristor prepared in Example 2 of the present invention.

[0025] Figure 3 The images show the IV test results of the memristor prepared in Example 2 of this invention under conditions of light and no light; the left image corresponds to no light and the right image corresponds to light.

[0026] Figure 4 The image shows the retention test results of the memristor prepared in Example 2 of this invention under conditions of added light and no light.

[0027] Figure 5 The image shows a pulse modulation test diagram of the memristor prepared in Embodiment 2 of the present invention. Detailed Implementation

[0028] The following examples are provided to further illustrate the present invention, but the examples do not limit the present invention in any way.

[0029] Example 1

[0030] like Figure 1 As shown, the perovskite composite thin film memristor provided by the present invention comprises, from bottom to top, a glass substrate, an ITO bottom electrode, a composite resistive switching layer, and a TiN top electrode; the composite resistive switching layer is composed of a lower molybdenum oxide layer and an upper methylamine lead iodide layer.

[0031] The ITO bottom electrode has a thickness of 80 nm, the composite resistive switching layer has a thickness of 120 nm, the molybdenum oxide layer has a thickness of 40 nm, the methylamine lead iodine layer has a thickness of 80 nm, and the TiN top electrode has a thickness of 40 nm. The TiN top electrode consists of several circular electrodes with a diameter of 50 μm uniformly distributed on the composite resistive switching layer.

[0032] Example 2

[0033] The method for preparing the perovskite composite thin film memristor provided by this invention includes the following steps:

[0034] (1) First, place the glass substrate in an acetone solution and ultrasonically clean it for 10 minutes to remove the stains on its surface. Then, place it in an alcohol solution and ultrasonically clean it for 10 minutes. After taking it out, blow it dry with high-purity nitrogen gas for later use.

[0035] (2) Use silver paste to attach the glass substrate to the heater tray.

[0036] (3) Place the heater tray with the glass substrate attached into the vacuum chamber. After closing the chamber's sealing door, turn on the mechanical pump, then slowly open the bypass valve. Once the pressure inside the chamber drops below 0.5 Pa, close the bypass valve. Turn on the molecular pump start switch, then slowly open the fore-stage valve and the gate valve until the pressure reaches 2 × 10⁻⁶ Pa. -4 Pa. Adjust the gate valve to a slightly open position and inject argon gas at a flow rate of 25 sccm into the chamber. Adjust the gate valve to stabilize the pressure inside the chamber at 0.5 Pa. To remove contaminants from the target surface, a 10-minute pre-deposition is performed before the formal deposition of the ITO thin film, followed by the formal deposition, which takes approximately 60 minutes. After the thin film deposition is complete, close the molecular pump valve and switch, and fill the chamber with argon gas, forming an ITO bottom electrode on the glass substrate with a thickness of 80 nm.

[0037] (4) Place the glass substrate into the vacuum chamber. After closing the chamber's sealing door, turn on the mechanical pump, then slowly open the bypass valve. Once the pressure inside the chamber drops below 0.5 Pa, close the bypass valve. Turn on the molecular pump start switch, then slowly open the fore-stage valve and gate valve until the pressure reaches 2 × 10⁻⁶ Pa. -4 Pa. Adjust the gate valve to a slightly open position and inject argon gas at a flow rate of 25 sccm into the chamber. Adjust the gate valve to stabilize the pressure inside the chamber at 0.5 Pa. To remove contaminants from the target surface, a 10-minute pre-deposition is performed before the formal deposition of the molybdenum oxide film, followed by the formal deposition, which takes approximately 60 minutes. After film deposition, the molecular pump valve and switch are closed, and argon gas is introduced into the chamber, forming a molybdenum oxide film with a thickness of 40 nm on the ITO bottom electrode.

[0038] Methylamine lead-iodine thin films were prepared using the sol-gel method. A methylamine lead-iodine precursor solution was prepared. A glass substrate with a molybdenum oxide thin film was placed on a spin coater. After the substrate was held in place, the spin coating time was set to 42 s and the rotation speed to 4000 rpm. After rotation was stopped, the substrate was placed on a heating stage for drying. The resulting methylamine lead-iodine thin film had a thickness of 80 nm.

[0039] A composite resistive switching layer is formed by combining molybdenum oxide thin film and methylamine lead iodine thin film.

[0040] (5) Place a mask on the substrate where the composite resistive switching layer is formed. The mask has evenly distributed circular holes with a diameter of 50 μm. Evacuate the cavity to 5 × 10⁻⁶. -4 Argon gas at a flow rate of 25 sccm is introduced into the cavity, and the interface valve is adjusted to maintain the pressure in the cavity at 0.8 Pa. The AC source controlling the target ignition is turned on, and the power of the AC source is adjusted to 15 W to ignite the target. Pre-sputtering is performed for 4-6 minutes. Then, formal sputtering is performed to form a TiN top electrode on the composite resistive switching layer. The sputtering time of the TiN top electrode is about 60 minutes, and the thickness is 40 nm.

[0041] The key to the memristor prepared by this invention is that a composite resistive switching layer of molybdenum oxide and methylamine lead iodine is obtained on a glass substrate by radio frequency magnetron sputtering and sol-gel method.

[0042] The above-described embodiments are any one of the preparation methods protected by this invention. As long as the process parameters described in the claims and specification are within the range (such as the substrate being a glass substrate, the cavity vacuum degree of magnetron sputtering, the RF source power, the pre-sputtering time, and the formal sputtering time, etc.), the memristor to be protected in Embodiment 1 of this invention can be obtained, and the prepared memristor has basically similar performance to the device prepared in this embodiment.

[0043] Performance testing

[0044] SEM images of the composite resistive switching layer of the memristor prepared in Example 2, such as... Figure 2 As shown. From Figure 2 As can be seen, the methylamine lead-iodine film has a dense structure and a very smooth surface, without large particles.

[0045] The IV performance of the memristor prepared in Example 2 was tested under both light-added and light-free conditions, such as... Figure 3 As shown, Figure 3 In the image, the left panel shows the IV performance without illumination, while the right panel shows the IV performance with illumination (405 nm wavelength, 20 mW energy). From... Figure 3 As can be seen, adding light can achieve a larger window, and the device has a significant response to light.

[0046] The retention characteristics of the memristor prepared in Example 2 were tested under both light-added and light-free conditions, such as... Figure 4 As shown. From Figure 4 As can be seen, after the light is applied, the resistance of the resistive switching element changes from a low resistance state to a high resistance state, and can maintain this state for 10 seconds. 4 Approximately s.

[0047] The simulated neural PPF performance of the memristor prepared in Example 2 was tested, such as... Figure 5As shown, two square wave pulses were applied to the device, successfully simulating the paired-pulse facilitation (PPF) characteristics. The first and second current spikes were defined as A1 and A2, respectively. The PPF exponent, defined as: PPF = A2 / A1 × 100%, was fitted as a function of the time interval between the two pulses.

[0048] The above embodiments are preferred embodiments of the present invention, but the embodiments of the present invention are not limited to the embodiments described above. Any changes, modifications, substitutions, combinations, or simplifications made without departing from the spirit and principle of the present invention shall be considered equivalent substitutions and shall be included within the protection scope of the present invention.

Claims

1. A perovskite composite thin-film memristor, characterized in that, Its structure, from bottom to top, includes: a glass substrate, an ITO bottom electrode, a composite resistive switching layer, and a TiN top electrode; wherein, the composite resistive switching layer is composed of a lower molybdenum oxide layer and an upper methylamine lead iodine layer.

2. The perovskite composite thin-film memristor according to claim 1, characterized in that, The thickness of the ITO bottom electrode is 80 nm, and the thickness of the composite resistive switching layer is 120 nm.

3. The perovskite composite thin-film memristor according to claim 1, characterized in that, The thickness of the TiN top electrode is 40 nm. The TiN top electrode includes several circular electrodes uniformly distributed on the composite resistive switching layer.

4. A method for fabricating a perovskite composite thin-film memristor, characterized in that, Includes the following steps: (1) Pretreatment of the glass substrate; (2) ITO bottom electrode was fabricated on a glass substrate by magnetron sputtering; (3) A molybdenum oxide layer is prepared on the ITO bottom electrode by magnetron sputtering, and a methylamine lead iodide layer is prepared on the molybdenum oxide layer by sol-gel method. The molybdenum oxide layer and the methylamine lead iodide layer are combined to form a composite resistive switching layer. (4) Prepare TiN top electrode on composite resistive switching layer.

5. The method for preparing a perovskite composite thin-film memristor according to claim 4, characterized in that, Step (3) The molybdenum oxide layer on the ITO bottom electrode is prepared by magnetron sputtering: the glass substrate is placed in the magnetron sputtering vacuum chamber, the vacuum is drawn and argon gas is injected, then pre-sputtering for 10 min, and then formal sputtering for 60 min to form a molybdenum oxide layer with a thickness of 40 nm on the ITO bottom electrode.

6. The method for preparing a perovskite composite thin-film memristor according to claim 4, characterized in that, Step (3) The preparation of the methylamine lead iodine layer on the molybdenum oxide layer using the sol-gel method is as follows: Prepare the methylamine lead iodine precursor solution, place the glass substrate with the molybdenum oxide layer on the spin coater, set the spin coating time to 42s and the rotation speed to 4000 rpm, and after stopping the rotation, place the glass substrate on the heating stage to dry, forming a methylamine lead iodine layer with a thickness of 80nm.

7. The method for preparing a perovskite composite thin-film memristor according to claim 4, characterized in that, Step (2) specifically involves placing the glass substrate into the magnetron sputtering vacuum chamber, evacuating it, injecting argon gas, pre-sputtering for 10 minutes, and then formally sputtering for 60 minutes to form an 80nm thick ITO bottom electrode.

8. The method for preparing a perovskite composite thin-film memristor according to claim 4, characterized in that, In step (4), before preparing the TiN top electrode, a mask is first placed on the glass substrate with circular holes of 50 μm in diameter evenly distributed on the mask. The glass substrate is placed in the magnetron sputtering vacuum chamber, a vacuum is drawn, and argon gas is injected. The AC source power is adjusted to make the target material glow. Pre-sputtering is performed for 4-6 minutes, followed by formal sputtering for 60 minutes to form a TiN top electrode with a thickness of 40 nm.

Images