Method for regulating and controlling thermal stability of CuInP2S6 device based on non-ferroelectric phase

Abstract

The invention discloses a method for regulating and controlling the thermal stability of a CuInP2S6 device based on a non-ferroelectric phase, which is characterized in that a method for regulating and controlling Cu ion defects and charge accumulation at an interface between a ferroelectric phase and a non-ferroelectric phase in a CuInP2S6 thin layer is adopted, and the thermal stability of the device is improved through a strong pinning effect. The method specifically comprises the following steps: preparing a CuInP2S6 thin layer, determining a phase change behavior and a strong pinning effect in the CuInP2S6 thin layer to promote the thermal stability of the CuInP2S6 thin layer, and the like. Compared with the prior art, the thermal stability of CuInP2S6 is remarkably improved, a new way is provided for development of controllable ferroelectric polarization switches and design of high-reliability and durable multifunctional devices, and the problem that in the prior art, the thermal stability of CIPS materials is insufficient in a high-temperature environment is effectively solved. Technical support is provided for application of the material in high-temperature electronic devices, and the material has a good application prospect.

Description

Technical Field

[0001] The present invention relates to the technical field of electrical research of electronic devices, and in particular to a method for regulating the thermal stability of a CuInP2S6 device based on a non-ferroelectric phase. Background Art

[0002] In recent years, two-dimensional materials, represented by graphene, have attracted widespread attention due to their unique optical, thermal, and electrical properties, as well as their promising applications in electronic devices. Among them, the two-dimensional van der Waals layered material CuInP2S6 (CIPS) has become a research hotspot due to its unique properties, including room-temperature ferroelectricity, strong coupling between ionic conductivity and ferroelectric polarization, negative piezoelectricity, and enhanced bulk photovoltaic effect. It also has great potential for application in memristors and optoelectronic devices. However, CuInP2S6 faces insufficient thermal stability in practical applications, especially at high temperatures, where the stability of the ferroelectric domains decreases significantly, limiting its application in high-temperature electronic devices. Although studies have shown that the thermal stability of CuInP2S6 can be improved by introducing a non-ferroelectric phase, the specific mechanism has not been thoroughly studied and verified. Therefore, developing methods to effectively manipulate the thermal stability of CuInP2S6, particularly through the introduction of a non-ferroelectric phase and the manipulation of interface defects, is crucial for improving the performance of CuInP2S6 materials and promoting their application in high-temperature electronic devices. Summary of the Invention

[0003] The purpose of the present invention is to provide a method for regulating the thermal stability of CuInP2S6 devices based on non-ferroelectric phases in response to the deficiencies of the existing technology. The method adopts a method of regulating the Cu ion defects at the interface between the ferroelectric phase and the non-ferroelectric phase in the CuInP2S6 thin layer to induce charge accumulation at the interface, maintain the original polarization state through the pinning field, thereby enhancing the thermal stability of the CuInP2S6 device. The method prepares CuInP2S6 thin layer samples by mechanical stripping, characterizes their ferroelectricity at room temperature, and determines the Cu through in-situ temperature-dependent Raman spectroscopy and PFM measurement. The phase transition behavior of the ferroelectric phase and non-ferroelectric phase in the InP2S6 thin layer under temperature changes, the Cu ion defects and charge accumulation at the interface of the ferroelectric phase and non-ferroelectric phase in the CuInP2S6 thin layer are utilized to promote its thermal stability through a strong pinning effect, which significantly improves the thermal stability of CuInP2S6. This provides a new approach for the development of controllable ferroelectric polarization switches and the design of high-reliability and durable multifunctional devices, effectively solves the problem of insufficient thermal stability of CIPS materials in high-temperature environments in existing technologies, provides technical support for its application in high-temperature electronic devices, and has good application prospects.

[0004] The specific technical solution for achieving the purpose of the present invention is: a method for regulating the thermal stability of a CuInP2S6 device based on a non-ferroelectric phase, which is characterized by adopting a method of regulating Cu ion defects at the ferroelectric phase / non-ferroelectric phase interface in a CuInP2S6 thin layer to induce charge accumulation at the interface, maintain the original polarization state through a pinning field, thereby enhancing the thermal stability of the CuInP2S6 device. The method specifically includes the following steps:

[0005] Step S1, preparing a CuInP2S6 thin layer sample by mechanical exfoliation, and characterizing its ferroelectricity at room temperature by piezoelectric force microscopy (PFM);

[0006] Step S2, determining the phase transition behavior of the ferroelectric phase and the non-ferroelectric phase in the CuInP2S6 thin layer under temperature changes by in-situ temperature-dependent Raman spectroscopy and PFM measurement;

[0007] Step S3: utilizing the Cu ion defects and charge accumulation at the interface between the ferroelectric phase and the non-ferroelectric phase in the CuInP2S6 thin layer to improve its thermal stability through a strong pinning effect.

[0008] Further preferably, in step S1, the method for preparing the CuInP2S6 thin layer sample specifically comprises the following steps:

[0009] S1-1, using magnetron sputtering technology to prepare a Pt film with a thickness of about 50 nm on a Si substrate;

[0010] S1-2, peeling the CuInP2S6 block multiple times on the transparent tape by mechanical stripping method, and transferring a small amount of sample from the tape using polydimethylsiloxane;

[0011] S1-3. After observation under an optical microscope, a CuInP2S6 thin layer with a thickness of about 80 nm was screened out by optical contrast and transferred to a substrate with a Pt thin film using a transfer table.

[0012] Further preferably, in the temperature-dependent PFM test, the heating stage accessory of the instrument is used to heat the sample to a specific temperature and maintain it for 10 minutes each time to ensure that the temperature is accurately transferred to the CuInP2S6 thin layer.

[0013] Further preferably, in the temperature-dependent Raman spectroscopy measurement, the sample is heated to a corresponding temperature and maintained for 10 minutes each time by the heating stage control of the MFP-3D.

[0014] Further preferably, in step S2, the in-situ temperature-dependent PFM test and Raman spectrum measurement of CuInP2S6 are performed during a heating process from 25°C to 80°C.

[0015] Further preferably, in step S3, the CuInP2S6 thin layer sample containing a non-ferroelectric phase and the pure ferroelectric phase CuInP2S6 thin layer sample are heat-treated, and the enhancement effect of the non-ferroelectric phase on the thermal stability of CuInP2S6 is verified by PFM.

[0016] Further preferably, the heat treatment process comprises heating the two thin layer samples from room temperature to about 80°C and then cooling them to room temperature.

[0017] Further preferably, in step S3, the CuInP2S6 thin layer sample containing a non-ferroelectric phase has a large number of Cu ion defects and extensive charge accumulation at the interface of the ferroelectric / non-ferroelectric region.

[0018] Further preferably, in step S3, the strong pinning effect is achieved through the strong interaction between defects and charges at the interface between the non-ferroelectric phase and the ferroelectric phase.

[0019] Compared with the prior art, the present invention has the following beneficial technical effects and significant technical progress:

[0020] 1) The present invention solves the problem of insufficient thermal stability of CuInP2S6 (CIPS) materials in high-temperature environments. Compared with traditional pure ferroelectric phase CIPS, the present invention introduces a non-ferroelectric phase and combines Cu ion defects and charge accumulation at the interface between the ferroelectric and non-ferroelectric phases, significantly improving the thermal stability of CIPS materials in high-temperature environments.

[0021] 2) This invention provides a thermal stability enhancement mechanism based on the non-ferroelectric phase and combined with interface defect regulation. Scanning transmission electron microscopy revealed the atomic structure and charge distribution characteristics at the interface between the ferroelectric and non-ferroelectric phases. It was found that Cu ion defects and charge accumulation at the interface significantly enhance the thermal stability of the material through a pinning effect, providing new insights into the design of high-performance and high-stability ferroelectric materials.

[0022] 3) This invention provides a new technical approach for regulating the thermal stability of two-dimensional ferroelectric materials. By combining the introduction of a non-ferroelectric phase with the manipulation of interface defects, it not only addresses the thermal stability issues of CIPS materials at high temperatures but also provides a valuable approach and guidance for studying the thermal stability of other two-dimensional ferroelectric materials. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 Flowchart of the present invention;

[0024] Figure 2 Schematic diagram of the PFM measurement device;

[0025] Figure 3 This is an optical image of the CuInP2S6 thin layer sample prepared in Example 1;

[0026] Figure 4 Graph showing the test results of CuInP2S6 containing a non-ferroelectric phase and a pure ferroelectric phase before and after the heat treatment of Example 1;

[0027] Figure 5 Schematic diagram of the interface states and characteristics between the ferroelectric and non-ferroelectric regions of CuInP2S6 in Example 1. DETAILED DESCRIPTION

[0028] The present invention adopts a mechanical exfoliation method to prepare CuInP2S6 thin layer samples, and characterizes their ferroelectricity at room temperature by piezoelectric force microscopy. Then, the phase transition behavior of the ferroelectric phase and non-ferroelectric phase in the CuInP2S6 thin layer under temperature changes is determined by in situ temperature-dependent Raman spectroscopy and PFM measurement. Finally, the thermal stability of the CuInP2S6 thin layer is improved by utilizing the Cu ion defects and charge accumulation at the interface between the ferroelectric phase and the non-ferroelectric phase in the CuInP2S6 thin layer through a strong pinning effect.

[0029] See Figure 1 , the present invention specifically includes the following steps:

[0030] Step S1: prepare a CuInP2S6 thin layer sample by mechanical exfoliation, and characterize its ferroelectricity at room temperature by piezoelectric force microscopy (PFM).

[0031] Step S2: Determine the phase transition behavior of the ferroelectric phase and the non-ferroelectric phase in the CuInP2S6 thin layer under temperature changes through in-situ temperature-dependent Raman spectroscopy and PFM measurement.

[0032] Step S3: utilizing the Cu ion defects and charge accumulation at the interface between the ferroelectric phase and the non-ferroelectric phase in the CuInP2S6 thin layer to improve its thermal stability through a strong pinning effect.

[0033] Below in conjunction with specific embodiment and accompanying drawing, the present invention is described in further detail.The process, conditions, reagents, experimental techniques etc. of implementing the present invention, except the content specifically mentioned below, are all common knowledge and common common sense in this area, and the present invention has no particular limitation content.Below by embodiment, the present invention is further elaborated, its purpose is in order to more thoroughly understand the content of the present invention, and all examples cited are not regarded as limitation to protection scope of the present invention.

[0034] Example 1

[0035] Step S1: Preparation of CuInP2S6 thin layer sample

[0036] A Pt film with a thickness of about 50 nm was prepared on a Si substrate using magnetron sputtering technology. The CuInP2S6 bulk was peeled off multiple times on a transparent tape by mechanical stripping, and a small amount of sample was transferred from the tape using polydimethylsiloxane to prepare a CuInP2S6 thin layer sample.

[0037] See Figure 2 , observed under a piezoelectric force microscope (PFM), and screened out a CuInP2S6 thin layer with a thickness of 80 nm by optical contrast, and transferred it to a substrate with a Pt thin film using a transfer table.

[0038] See Figure 3 The ferroelectric properties of the prepared CuInP2S6 thin layer sample were characterized at room temperature using piezoelectric force microscopy (PFM). The image showed that there were three regions, each exhibiting different piezoelectric responses, including ferroelectric phase region 1, ferroelectric phase region 2, and non-ferroelectric phase region.

[0039] Step S2: In situ temperature-dependent PFM measurements and Raman spectroscopy tests were performed on the prepared CuInP2S6 thin layer sample in the temperature range of 25°C to 80°C to verify the reversibility of the thermally induced phase transition of the prepared CuInP2S6 material containing a non-ferroelectric phase.

[0040] Step S3: utilizing the Cu ion defects and charge accumulation at the interface between the ferroelectric phase and the non-ferroelectric phase in the CuInP2S6 thin layer to improve its thermal stability through a strong pinning effect.

[0041] To manipulate the thermal stability of CuInP2S6 at high temperatures based on the non-ferroelectric phase, this example heat-treated CuInP2S6 thin layer samples containing a non-ferroelectric phase (CIPS-FE / NFE) and a pure ferroelectric CuInP2S6 thin layer sample (CIPS-FE). Both samples were first heated from room temperature to approximately 80°C and then cooled to room temperature. PFM images were used to capture the response before and after heating, and domain wall contours were extracted.

[0042] See Figure 4 Comparison of the domain information of the CIPS-FE / NFE sample and the CIPS-FE sample before and after heat treatment revealed that the ferroelectric domain structure of the CIPS-FE / NFE sample remained virtually unchanged before and after heat treatment, demonstrating excellent thermal stability. However, the domain pattern of the CIPS-FE sample underwent significant changes after heat treatment. Therefore, the non-ferroelectric CuInP2S6 phase proposed in this paper exhibits superior thermal stability compared to the pure ferroelectric CuInP2S6 phase, which lacks a non-ferroelectric phase.

[0043] Based on the CuInP2S6 thin layer sample containing a non-ferroelectric phase prepared in Example 1, the role of the non-ferroelectric phase region in stabilizing the ferroelectric domain was verified through atomic structure and charge distribution.

[0044] See Figure 5 a, STEM-HAADF imaging of the atomic structure of a CuInP2S6 thin layer reveals a darker contrast between the non-ferroelectric region and the ferroelectric phase, further confirming the absence of Cu ions in the non-ferroelectric region. Furthermore, a distinct transition region is observed at the ferroelectric / non-ferroelectric interface, which is primarily composed of an ordered ferroelectric phase structure but contains a large number of dark-contrast point defects caused by Cu ion defects.

[0045] To further investigate charge distribution, this example used DPC to measure the horizontal electric field distribution in a CuInP2S6 thin layer. The results showed that the electric field distribution in the non-ferroelectric region exhibited weak contrast and irregular colors, confirming its lack of polarization; in contrast, the ferroelectric region contained domains with distinct polarization directions. Furthermore, significant charge accumulation was observed at the ferroelectric / non-ferroelectric interface. These defects and charge accumulation stabilized the ferroelectric domain structure through a strong pinning effect, significantly improving the thermal stability of the material.

[0046] See Figure 5 b, According to the principle of the above mechanism, the strong coupling between Cu ion defects and charges induces charge accumulation and provides a pinning field to maintain the original polarization state, thereby enhancing thermal stability and information reliability. c When the temperature is close to T c When the ferroelectric response weakens, the ferroelectric region begins to shrink, the domain wall increases, and the amplitude signal decreases. During the cooling process, the domain structure around the pinning center is usually well restored and preserved. This example further verifies the effectiveness of the non-ferroelectric phase proposed in this invention to regulate the thermal stability of CuInP2S6 through the pinning effect through a comprehensive analysis of atomic structure, charge distribution, and thermal evolution behavior.

[0047] The protection content of the present invention is not limited to the above embodiments. Without departing from the spirit and scope of the inventive concept, changes and advantages that can be thought of by those skilled in the art are included in the present invention and are protected by the appended claims.

Claims

1. A method for controlling the thermal stability of a CuInP2S6 device based on a non-ferroelectric phase, characterized in that: By regulating the Cu ion defects at the ferroelectric / non-ferroelectric phase interface, charge accumulation is induced at the interface, and the original polarization state is maintained by the pinning field, thereby enhancing the thermal stability of the CuInP2S6 device. The method specifically includes: Step S1: using a piezoelectric force microscope to characterize the ferroelectric properties of the CuInP2S6 thin layer prepared by mechanical exfoliation at room temperature; Step S2: using in-situ temperature-dependent Raman spectroscopy and PFM measurements to determine the phase transition behavior of the ferroelectric and non-ferroelectric phases in the CuInP2S6 thin layer under temperature changes; Step S3: utilizing the Cu ion defects and charge accumulation at the interface between the ferroelectric phase and the non-ferroelectric phase in the CuInP2S6 thin layer to improve its thermal stability through a strong pinning effect.

2. The method for controlling the thermal stability of a CuInP2S6 device based on a non-ferroelectric phase according to claim 1, characterized in that: The preparation of the CuInP2S6 thin layer in step S1 specifically includes the following steps: S1-1: Pt thin film with a thickness of about 50 nm was prepared on Si substrate using magnetron sputtering technology; S1-2: The CuInP2S6 bulk was peeled off multiple times on a transparent tape by mechanical peeling, and a small amount of sample was transferred from the tape using polydimethylsiloxane; S1-3: A CuInP2S6 thin layer with a thickness of 80 nm was screened out by optical contrast and transferred to a substrate with a Pt thin film using a transfer table.

3. The method for controlling the thermal stability of CuInP2S6 devices based on non-ferroelectric phase according to claim 1, characterized in that: The temperature-dependent PFM test in step S2 uses the instrument's heating stage accessory to heat the sample to 25-80°C and hold it for 10 minutes each time. The temperature-dependent Raman spectroscopy measurement is controlled by the MFP-3D's heating stage to heat the sample to 25-80°C and hold it for 10 minutes each time.

4. The method for controlling the thermal stability of a CuInP2S6 device based on a non-ferroelectric phase according to claim 1, wherein: In step S3, the CuInP2S6 thin layer sample containing a non-ferroelectric phase and the CuInP2S6 thin layer sample containing a pure ferroelectric phase are heat-treated, and the enhancement effect of the non-ferroelectric phase on the thermal stability of CuInP2S6 is verified by using PFM. The heat treatment heats the two thin layer samples from room temperature to about 80°C and then cools them to room temperature.

5. The method for controlling the thermal stability of CuInP2S6 devices based on non-ferroelectric phase according to claim 1, characterized in that: The strong pinning effect in step S3 is achieved by the strong interaction between defects and charges at the interface between the non-ferroelectric phase and the ferroelectric phase.

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