Ag < + > / Sm < 3 + > doped PN junction-containing perovskite single crystal, memristor and preparation method thereof

Abstract

The invention discloses an Ag < + > / Sm < 3 + >-doped PN junction-containing perovskite single crystal, a memristor and a preparation method of the Ag < + > / Sm < 3 + >-doped PN junction-containing perovskite single crystal. The preparation method of the Ag < + > / Sm < 3 + >-doped PN junction-containing perovskite single crystal comprises the following steps: dissolving MAX, PbX2 and AgX in a solvent, carrying out stirring treatment, then carrying out heating crystallization treatment, and growing to obtain an Ag < + >-doped P-type MAPbX3 single crystal, the preparation method comprises the following steps: dissolving MAX, PbX2 and SmX3 in a solvent, stirring, immersing into an Ag < + >-doped P-type MAPbX3 single crystal, and heating and crystallizing, so that an Sm < 3 + >-doped N-type MAPbX3 single crystal grows on the surface of the Ag < + >-doped P-type MAPbX3 single crystal in an epitaxial manner, thereby obtaining the Ag < + > / Sm < 3 + >-doped PN junction-containing perovskite single crystal. According to the invention, the PN junction is accurately constructed in the perovskite single crystal by using a solution method in-situ growth technology, so that the self-rectification effect and the memristive function of the device are realized, and a new technical approach is provided for the development of a high-performance and high-density memristive device.

Description

Technical Field

[0001] The present invention relates to the technical field of perovskite memristors, and in particular to an Ag + / Sm 3+ -doped perovskite single crystal containing a PN junction, a memristor and a preparation method thereof. Background Art

[0002] In recent years, in the field of memristors, perovskite materials have attracted much attention because they can achieve non-volatile switching of resistance by regulating internal ion migration, defect states or phase transitions. This resistance switching behavior not only has the characteristics of fast speed and low power consumption, but also can achieve multiple resistance states, providing the possibility for high-density information storage. However, although significant progress has been made in laboratory research on perovskite memristors, they still face challenges in terms of stability and reliability.

[0003] Most traditional perovskite memristors adopt a thin-film structure. Their preparation process is complex and difficult to precisely control. The uniformity, thickness and crystal quality of the thin film have a direct impact on the performance and reliability of the device. Problems such as grain boundaries, defects and phase transitions in the thin film will lead to unstable resistance switching behavior, short device life and high power consumption of the device. In addition, most perovskite memristors require additional rectifying devices (such as diodes) to achieve unidirectional conductivity to solve the "sneak path" problem in crossbar arrays. This not only increases the complexity and manufacturing cost of the device, but also limits the integration density of the device.

[0004] Current research mainly focuses on optimizing the performance of memristors by regulating the composition, structure and defects of perovskite thin films. For example, by introducing different dopants, changing the thin-film preparation process or designing new device structures, the ion migration and resistance switching behavior of perovskite materials can be regulated. However, these methods still have certain limitations in improving the stability and reliability of devices. Summary of the Invention

[0005] The main object of the present invention is to provide an Ag + / Sm 3+ -doped perovskite single crystal containing a PN junction, a memristor and a preparation method thereof.

[0006] To achieve the above object, the present invention provides a preparation method of an Ag + / Sm 3+ -doped perovskite single crystal containing a PN junction, comprising the following steps:

[0007] (1) Growth of an Ag + -doped P-type MAPbX3 single crystal

[0008] Dissolve MAX, PbX2, and AgX in a solvent, stir, and then perform heat crystallization to grow Ag + doped P-type MAPbX3 single crystal;

[0009] (2) Sm 3+ Growth of Sm-doped N-type MAPbX3 single crystal

[0010] Dissolve MAX, PbX2, and SmX3 in a solvent, stir, and then immerse in Ag + doped P-type MAPbX3 single crystal, and then perform heat crystallization to cause Sm + to epitaxially grow on the surface of the doped P-type MAPbX3 single crystal 3+ doped N-type MAPbX3 single crystal, thus obtaining the Ag + / Sm 3+ doped perovskite single crystal containing a PN junction;

[0011] All of the above X represents a halogen atom.

[0012] Further, in step (1), the solvent is DMF, and the molar ratio of MAX, PbX2, and AgX is 1:1:0.1.

[0013] Further, in step (1), the specific process of heat crystallization is as follows: first heat at 90 °C for 20 min, then gradually increase the temperature to 100 - 120 °C within 30 - 60 min to grow a single sub-crystal, and finally keep the temperature constant at 90 °C for crystallization for 3 - 5 h.

[0014] Further, in step (2), the solvent is DMF, and the molar ratio of MAX, PbX2, and SmX3 is 1:1:0.1.

[0015] Further, in step (2), the specific process of heat crystallization is as follows: keep the temperature constant at 90 °C for crystallization for 3 - 6 h.

[0016] Further, the growth rate of the perovskite single crystal can be adjusted by changing the concentration of the precursor solution.

[0017] Further, the growth rate of the perovskite single crystal can be adjusted by changing the temperature of perovskite single crystal growth.

[0018] The present invention also provides an Ag + / Sm 3+ doped perovskite single crystal containing a PN junction, which is prepared according to the above preparation method.

[0019] The present invention also provides a perovskite single crystal memristor containing a PN junction, including the above Ag + / Sm 3+Doped perovskite single crystal containing a PN junction, and two metal electrodes respectively attached to the P-type MAPbX3 single crystal and the N-type MAPbX3 single crystal of the perovskite single crystal containing a PN junction.

[0020] Further, the materials of the two metal electrodes are independently selected from Au and Ag respectively.

[0021] Further, the thickness of the metal electrode is 30-100 nm, and the distance between the two metal electrodes is 10-300 μm.

[0022] The present invention also provides a method for preparing the perovskite single crystal memristor containing a PN junction as described above, including the following steps: First, polish both ends of the perovskite single crystal containing a PN junction until the doped P-type MAPbX3 single crystal is exposed, and then use electron beam coating to evaporate the metal electrodes on the P-type MAPbX3 single crystal and the N-type MAPbX3 single crystal of the perovskite single crystal containing a PN junction respectively. + Further, the distance and shape between the two metal electrodes are controlled by covering with different masks, and the evaporation rate is

[0023] The performance of the perovskite single crystal memristor containing a PN junction of the present invention can be adjusted by different combinations of the metal type of the metal electrode, the channel width, the doping concentration of different metal elements, and the types of different metals.

[0024] Idea and principle of the present invention:

[0025] The present invention uses solution method in-situ growth technology to precisely construct a PN junction inside the perovskite single crystal, thereby realizing the self-rectifying effect and memristive function of the device. Specifically, Ag and Sm are introduced respectively through two-step growth.

[0026] and Sm + 3+ ​Doping and modifying perovskite single crystals with metal ions forms P-type and N-type regions within the single crystal, enabling the construction of a high-quality PN junction between the two. Due to the built-in electric field of the PN junction, the device exhibits an obvious unidirectional conduction characteristic in electrical property characterization: when a negative bias voltage is applied, the current easily passes through the PN junction, and the device presents a low-resistance state (LRS); while when a positive bias voltage is applied, the current is inhibited, and the device maintains a high-resistance state (HRS), thus realizing the self-rectifying effect. In addition, by applying different voltage pulses, the ion migration and defect states within the PN junction region can be effectively regulated, achieving reversible switching of the device resistance between the high and low resistance states, endowing the device with memristive function. This self-rectifying memristor structure based on in-situ growth of PN junctions, the in-situ growth method ensures the interface quality and doping uniformity, improves the stability and reliability of the device, not only simplifies the device design and improves the integration degree, but also realizes stable resistance switching and excellent self-rectifying characteristics by controlling ion migration and defect states. The present invention utilizes the excellent properties of perovskite single crystals and the rectifying characteristics of PN junctions, providing a new technical approach for the development of high-performance and high-density memristive devices.

[0027] The beneficial effects of the present invention are as follows:

[0028] The solution method for in-situ growth of single crystals adopted in the present invention solves the problems existing in perovskite memristors with traditional thin-film structures, such as poor thin-film uniformity, the need for additional rectifying devices, poor stability, and difficulty in controlling ion migration. The core innovation of the present invention lies in: in-situ growing a PN junction on a MAPbX3 single-crystal substrate by using the solution method, and doping with Ag + and Sm 3+ metal ions to construct a high-quality PN junction inside the single crystal. This structure endows the device with the following significant beneficial effects:

[0029] 1. Simplify the device structure and improve the integration degree: By virtue of the built-in electric field of the PN junction, the self-rectifying effect is realized, eliminating the need for additional rectifying diodes, solving the sneak path problem in crossbar arrays, significantly simplifying the device structure, enhancing the integration density, and reducing the manufacturing cost.

[0030] 2. Improve the stability and reliability of the device: Adopting a single-crystal substrate and in-situ growing a PN junction effectively reduces interface defects and grain boundaries, improves the interface quality and charge transport efficiency, thus significantly enhancing the stability and reliability of the device.

[0031] 3. Precisely regulate electrical properties: By controlling the types and concentrations of doped ions, precise regulation of the electrical properties of perovskite materials is achieved, optimizing the resistance switching behavior of the device, and realizing low-power and high-sensitivity memristive characteristics.

[0032] 4. Simple and controllable preparation process: The in-situ growth process of the PN junction by the solution method is relatively simple and easy to control, achieving a uniform distribution of doped ions and ensuring the formation of a high-quality PN junction. Description of the Drawings

[0033] Figure 1 Schematic diagram of the preparation process of the memristor according to an embodiment of the present invention.

[0034] Figure 2 Graph of the current-voltage test results of the memristor according to an embodiment of the present invention. Detailed Description of the Embodiments

[0035] In order to make those skilled in the art more clearly understand the technical solutions described in the present invention, the following embodiments are listed for illustration. It should be noted that the following embodiments do not limit the protection scope required by the present invention.

[0036] Unless otherwise specified, the raw materials, reagents or devices used in the following embodiments can be obtained from conventional commercial channels or can be obtained by existing known methods; unless otherwise specified, the methods used in the embodiments of the present invention are all methods mastered by those skilled in the art.

[0037] Example 1

[0038] Ag + / Sm 3+ Preparation of Ag

[0039] The preparation process is shown in Figure 1 .

[0040] (1) Preparation of the device

[0041] Prepare two 10-ml glass bottles, blow dry the inside of the glass bottles with a nitrogen gun, clean the magnetic stirrers with an ultrasonic cleaner, then blow dry the attached deionized water with a nitrogen gun and dry it in a vacuum drying oven.

[0042] (2) Growth of Ag + -doped P-type MAPbBr3 single crystal

[0043] Mix 0.1 mmol of methylammonium bromide (MABr), 0.1 mmol of lead bromide (PbBr2), 0.01 mmol of silver bromide (AgBr) with 1 ml of dimethylformamide (DMF), stir for 1 h, filter through a filter plug with a pore size of 0.22 μm, and then pour the filtrate into a glass bottle.

[0044] Place the glass bottle on a heating stage at 90 °C and heat it for 20 min. Then, heat it at a rate of 1 °C / min until a single sub-crystal appears in the solution (usually between 100 and 120 °C). Then, transfer the glass bottle to a heating stage at 90 °C and grow it isothermally for 4 h. An Ag crystal with a side length of about 3 - 5 mm grows in the glass bottle. + For the Ag-doped P-type MAPbBr3 single crystal, use tweezers to take out the single crystal and quickly transfer it to absorbent paper to absorb the excess solution on the surface.

[0045] (3) Growth of Sm 3+ -doped N-type MAPbBr3 single crystal

[0046] Mix 0.1 mmol of methylammonium bromide (MABr), 0.1 mmol of lead bromide (PbBr2), 0.01 mmol of samarium bromide (SmBr3) with 1 ml of dimethylformamide (DMF) and stir for 1 h. After filtering with a filter plug with a pore size of 0.22 μm, pour it into a glass bottle, and then immerse it in the Ag + -doped P-type MAPbBr3 single crystal obtained in step (1);

[0047] Place the glass bottle on a heating stage at 90 °C and grow it isothermally for 5 h, so that an Sm + -doped N-type MAPbBr3 single crystal grows epitaxially on the surface of the Ag 3+ -doped P-type MAPbBr3 single crystal. The combination of the two is the Ag + / Sm 3+ -doped perovskite single crystal with a PN junction, with a side length of about 6 - 10 mm. Use tweezers to take out the single crystal and quickly transfer it to absorbent paper to absorb the excess solution on the surface.

[0048] (4) Evaporation of metal electrodes

[0049] Use fine sandpaper to grind off 2.2 - 3.0 mm from each end of the perovskite single crystal with a PN junction obtained in step (3), leaving only the middle part with a thickness of about 2 - 3 mm. At this time, on the surfaces at both ends of the middle part: in the middle is the Ag + -doped P-type MAPbBr3 single crystal, and on the periphery is the Sm 3+ -doped N-type MAPbBr3 single crystal. Rinse the surface of the middle part with DMF solvent and dry it on a heating stage at 60 °C for 30 min;

[0050] Adopt the method of electron beam coating, at a rate of to evaporate the electrodes under a vacuum of 10 -6 Torr. Evaporate silver electrode 1 on the Sm 3+ -doped N-type MAPbBr3 single crystal on one end face of the middle part.+ Gold electrodes 2 are deposited on the doped p-type MAPbBr3 single crystal. The thicknesses of the silver electrode 1 and the gold electrode 2 are controlled within 30 - 100 nm. Different custom-made masks are used to cover the way to determine the distance between the two metal electrodes. The distance between the silver electrode 1 and the gold electrode 2 is controlled within 10 - 300 μm, and a perovskite single crystal memristor containing a PN junction is obtained.

[0051] Experimental Example 1

[0052] Performance Test of the Perovskite Single Crystal Memristor Containing a PN Junction

[0053] The specifications of the memristor selected for the test are as follows: The overall size of the perovskite single crystal containing a PN junction is 8 * 8 mm, and its Ag + The size of the doped p-type MAPbBr3 single crystal is 4 * 4 mm. After polishing, the remaining middle part has a thickness of 2.5 mm. The silver electrode 1 and the gold electrode 2 have a size of 1 μm * 1 μm and a thickness of 30 nm, and the distance between the silver electrode 1 and the gold electrode 2 is 100 μm.

[0054] The method for testing and characterizing the electrical properties of the memristor is as follows: The electrical properties of the memory are measured using a Keysight B1500A semiconductor parameter analyzer on a probe station and an inverted microscope. The voltage is applied in a backscanning manner. The test results are shown in Figure 2 , during the negative voltage backscanning process of the perovskite single crystal memristor containing a PN junction, a sudden change from the high resistance state (HRS) to the low resistance state (LRS) occurs, while in the positive voltage backscanning process, the high resistance state (HRS) is maintained, showing a self-rectifying effect.

[0055] The method for testing and characterizing the opto-synaptic properties of the memristor is as follows: The resistive switching performance of the device is measured using a Keysight B1500A semiconductor parameter analyzer on a probe station and an inverted microscope. The test results are shown in Figure 2 .

[0056] Figure 2 The self-rectifying characteristics and resistance switching behavior of the memristive device are shown in detail. It is the current-voltage (I-V) characteristic curve of a memristive device, revealing its unique working principle. The abscissa is the voltage (V), ranging from -3V to +3V, and the ordinate is the current (A), represented in logarithmic coordinates, ranging from 1E-11A to 0.1A. There are two obvious curves in the figure, representing different voltage scanning directions respectively, revealing the resistive switching behavior and self-rectifying characteristics of the device.

[0057] First, when the voltage is scanned negatively from 0V to -3V, the device initially remains in the high resistance state (HRS), and the current stays at a relatively low level (about 1E-7 A). As the negative voltage increases, the current rises slowly until it reaches a threshold voltage (about -1V), at which point the device suddenly undergoes a resistive change and jumps from the high resistance state to the low resistance state (LRS), and the current rapidly increases to above 0.01 A. During the process of the negative voltage being swept back to 0V, the device remains in the low resistance state and the current gradually decreases.

[0058] Then, when the voltage is scanned positively from 0V to +3V, the device always remains in the high resistance state, and the current is maintained at a relatively low level (between 1E-7 A and 1E-6 A), with almost no obvious resistive change phenomenon. During the process of the positive voltage being swept back to 0V, the device also remains in the high resistance state.

[0059] This asymmetric I-V characteristic indicates that the memristive device has an obvious self-rectifying effect, that is, it is prone to resistive change under negative voltage, while it is difficult to have a resistive change under positive voltage. This characteristic may stem from mechanisms such as the PN junction structure or Schottky barrier inside the device.

[0060] In addition, the figure also shows the resistance switching behavior of the device between the high and low resistance states. During the negative voltage scan, the resistance of the device switches from the high resistance state (about 10^7 ohms) to the low resistance state (about 10^2 ohms), and the resistance change amplitude reaches about 10^5 times, that is, the current switching ratio is ~10 5 . This large current switching ratio is crucial for the non-volatile storage and neuromorphic computing applications of memristors.

[0061] The present invention takes the MAPbBr3 perovskite single crystal as an example only for explaining the present invention, rather than for limiting the invention. Using other halogen perovskite materials as the matrix materials of the PN junction, such as CsPbI3, CsPbCl3, MAPbBr3, MAPbI3 and other materials, and using solution methods to achieve P-type doping and N-type doping regulation to form high-quality in-situ grown PN junction perovskite single crystals should also fall within the protection scope of the claims appended to the present invention.

[0062] The present invention takes the Au / Ag asymmetric electrode only for explaining the present invention, rather than for limiting the invention. Self-rectifying memristors prepared using other electrode combinations, such as Cr / Cu, Cr / Ni, etc., symmetric electrodes, such as Au / Au, etc., and asymmetric electrodes, such as Cr / Cu-Cr / Au, Cr / Ag-Cr / Au, Cr / Ni-Cr / Au, etc., should also fall within the protection scope of the claims appended to the present invention.

[0063] The above are only the preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principles of the present invention shall be included within the protection scope of the present invention.

Claims

1. A kind of Ag + / Sm 3+ Preparation method of perovskite single crystal doped with PN junction, characterized in that It includes the following steps: (1)Ag + (1) Growth of doped P-type MAPbX3 single crystals Dissolve MAX, PbX2, and AgX in a solvent, stir, and then perform heat crystallization treatment to grow Ag + doped P-type MAPbX3 single crystal; (2)Sm 3+ (2) Growth of doped N-type MAPbX3 single crystals Dissolve MAX, PbX2, and SmX3 in a solvent, stir, and then immerse in Ag + Dope P-type MAPbX3 single crystal, and then perform heat crystallization treatment to make Ag + On the surface of the doped P-type MAPbX3 single crystal, Sm 3+ Doped N-type MAPbX3 single crystal grows epitaxially, thus obtaining the Ag + / Sm 3+ Doped perovskite single crystal containing a PN junction; All of the above X represents a halogen atom.

2. The Ag as claimed in claim 1 + / Sm 3+ A method for preparing a doped perovskite single crystal containing a PN junction, characterized in that In step (1), the solvent is DMF, and the molar ratio of MAX, PbX2 and AgX is 1:1:0.

1.

3. The Ag as claimed in claim 1 or 2 + / Sm 3+ A method for preparing a doped perovskite single crystal containing a PN junction, characterized in that In step (1), the specific process of heat crystallization treatment is as follows: first heat at 90 °C for 20 min, then gradually increase the temperature to 100 - 120 °C within 30 - 60 min to grow a single daughter crystal, and finally carry out isothermal crystallization at 90 °C for 3 - 5 h.

4. The Ag as claimed in claim 1 or 2 + / Sm 3+ A method for preparing a doped perovskite single crystal containing a PN junction, characterized in that In step (2), the solvent is DMF, and the molar ratio of MAX, PbX2 and SmX3 is 1:1:0.

1.

5. The Ag as claimed in claim 1 or 2 + / Sm 3+ A method for preparing a doped perovskite single crystal containing a PN junction, characterized in that In step (2), the specific process of heat crystallization treatment is as follows: carry out isothermal crystallization at 90 °C for 3 - 6 h.

6. A kind of Ag + / Sm 3+ doped perovskite single crystal containing a PN junction, characterized in that It is prepared by the preparation method according to any one of claims 1 to 5.

7. A perovskite single crystal memristor containing a PN junction, characterized in that, Including Ag as described in claim 6 + / Sm 3+ A doped perovskite single crystal containing a PN junction, and two metal electrodes respectively attached to the P-type MAPbX3 single crystal and the N-type MAPbX3 single crystal of the perovskite single crystal containing the PN junction.

8. The perovskite single crystal memristor containing a PN junction according to claim 7, characterized in that, The materials of the two metal electrodes are independently selected from Au and Ag respectively.

9. The perovskite single crystal memristor containing a PN junction according to claim 7 or 8, characterized in that, The thickness of the metal electrode is 30 - 100 nm, and the distance between the two metal electrodes is 10 - 300 μm.

10. The preparation method of the perovskite single crystal memristor containing a PN junction according to claim 7 or 8 or 9, characterized in that, It includes the following steps: First, both ends of the perovskite single crystal containing a PN junction are polished until the Ag-doped P-type MAPbX3 single crystal is exposed. Then, the metal electrodes are respectively evaporated on the P-type MAPbX3 single crystal and the N-type MAPbX3 single crystal of the perovskite single crystal containing a PN junction by means of electron beam coating. + ​

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