Zinc sulfide film material with longitudinal piezoelectric effect and preparation method thereof

Abstract

The invention belongs to the technical field of piezoelectric materials, and particularly relates to a zinc sulfide thin film material with a longitudinal piezoelectric effect and a preparation method of the zinc sulfide thin film material. Undoped ZnS is used as a piezoelectric active material, a physical vapor deposition technology is adopted, a lower electrode layer and a ZnS piezoelectric active layer are sequentially prepared on a rigid or flexible substrate, and the lt is constructed by regulating and controlling technological parameters such as the deposition temperature; 111gt, 111gt; the XRD (X-Ray Diffraction) of the crystal orientation fiber texture only shows lt; 111gt, 111gt; diffraction peak and rocking curve full width at half maximum lt; 9 degrees. The piezoelectric coefficient d33 of the material is 5-25 pm / V, the positive piezoelectricity is linear without hysteresis, the inverse piezoelectric hysteresis is derived from ion migration, the cost is low, the environmental toxicity is avoided, the material is compatible with a semiconductor process, the technical blank related to the longitudinal piezoelectric property of zinc sulfide is filled, and the material is suitable for one-way precision sensing and quasi-static measurement scenes.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of piezoelectric materials, and particularly relates to a zinc sulfide film material with longitudinal piezoelectric effect and a preparation method thereof. BACKGROUND

[0002] Zinc sulfide (ZnS) is a piezoelectric material with potential application value, and its related research currently mainly focuses on composite material system construction and application exploration in the field of piezoelectric catalysis. In the existing technical practice, various functional application schemes based on ZnS have emerged, and a typical case is a zinc oxide-zinc sulfide (ZnO-ZnS) composite piezoelectric catalyst: the material is constructed into a heterojunction structure by a microwave-oil bath method to improve the piezoelectric catalytic hydrogen evolution efficiency, and the core mechanism is the interface charge transfer effect, rather than the active regulation of the intrinsic piezoelectric coefficient of ZnS. Another type of technology focuses on the preparation of piezoelectric films in the field of underwater acoustic wave detection: the nanoscale zinc sulfide is mixed into a polyvinylidene fluoride-trifluoroethylene (PVDF-TrFE) polymer matrix as an inorganic filler, the surface negative charge of ZnS induces the polymer matrix to form a beta crystal phase, and the stress transfer is assisted, and finally the piezoelectric response performance of the polymer composite film is improved.

[0003] Although the above two types of technologies are developed around the piezoelectric characteristics of ZnS, the technical cores of the two types of technologies are limited to d 14 Shear piezoelectric mode: the former relies on the shear deformation between particles to drive charge separation, and the latter completes force-electric coupling through the shear stress transfer of the polymer matrix. It is worth noting that both types of technologies do not involve the longitudinal piezoelectric effect (d 33 ) of the zinc sulfide material itself, and neither of them carries out systematic design and optimization for the lattice orientation and intrinsic piezoelectric tensor of ZnS. Since the longitudinal piezoelectric effect (d 33 ) has the advantages of high force-electric conversion efficiency, fast response speed, and clear directionality, it has irreplaceable application value in high-precision piezoelectric sensors, micro piezoelectric actuators, and high-efficiency energy collection devices. The neglect of the longitudinal piezoelectric characteristics of ZnS in the existing technology limits its application potential in the field of high-end piezoelectric devices.

[0004] Therefore, it is of important research value and application necessity to develop a zinc sulfide film material with significant longitudinal piezoelectric effect, and to realize the synergistic regulation of the longitudinal piezoelectric coefficient d 33 and the positive piezoelectric linear response. SUMMARY

[0005] In order to overcome the shortcomings of the prior art, the application provides a zinc sulfide film material with longitudinal piezoelectric effect and a preparation method thereof. The ZnS film material with <111> fiber texture is constructed in a directional manner, so that the intrinsic high piezoelectric coefficient (d 33Synergistic regulation of the positive piezoelectric linear response.

[0006] To achieve the above-mentioned purpose, the technical scheme adopted by the present application is: The present application provides a zinc sulfide film material with longitudinal piezoelectric effect in the first aspect, which comprises a ZnS piezoelectric active layer and a lower electrode layer stacked in sequence, the ZnS piezoelectric active layer has fiber texture along <111> crystal direction and d 33 The piezoelectric response characteristics, and its positive piezoelectric effect is linear and non-hysteresis, and the inverse piezoelectric response exists hysteresis phenomenon caused by ion migration.

[0007] Preferably, only ZnS <111> diffraction peak appears in the XRD pattern of the ZnS piezoelectric active layer, and the half-height width of the rocking curve of the diffraction peak is less than 9°.

[0008] Preferably, the d 33 Value is 5-25 pm / V.

[0009] The second aspect of the present application also provides a preparation method of the zinc sulfide film material with longitudinal piezoelectric effect in the first aspect, specifically: taking undoped ZnS as the piezoelectric active material, using physical vapor deposition technology to prepare the ZnS piezoelectric active layer on a rigid or flexible substrate, and then preparing the lower electrode layer to obtain the zinc sulfide film material with longitudinal piezoelectric effect. The vacuum cavity is pumped to a background vacuum degree of ≤5×10 -5 Pa before deposition, and the distance between the substrate and the target material is controlled to be 50-70 mm; the substrate heating temperature is maintained at 200-800℃ during the deposition process, the laser energy is set to 150-300 mJ, and the pulse frequency is 7-15 Hz.

[0010] The present application first proposes a zinc sulfide film material with longitudinal piezoelectric effect, which realizes the single arrangement of the macroscopic polarization axis by directional construction of <111> fiber texture, and directly stimulates the intrinsic d 33 Piezoelectric coefficient of ZnS. Among them, undoped ZnS is selected as the piezoelectric active material, the material defects are reduced by adjusting the preparation process parameters, the crystal structure order is enhanced, and the piezoelectric response ability is improved; by adjusting the preparation process of the lower electrode, the interface matching of the electrode and the ZnS film is optimized, a stable chemical interface is constructed, the charge transfer efficiency is improved, and the stability and consistency of the piezoelectric performance are enhanced. Compared with the composite material system based on the shear mode in the prior art, the zinc sulfide film material constructed by the present application does not need to rely on the hetero-interface or the polymer matrix, solves the technical blank of unknown longitudinal piezoelectric performance of zinc sulfide and missing texture growth mechanism, and provides an intrinsic performance solution for lead-free piezoelectric materials in the field of one-way precise sensing and quasi-static measurement.

[0011] Preferably, the vacuum chamber is pumped to a base pressure of ≤ 5 x 10 -5 The distance between the substrate and the target material is controlled to be 60 mm; the substrate heating temperature is maintained at 200-800 DEG C during the deposition process, the laser energy is set to be 200 mJ, and the pulse frequency is 20 Hz.

[0012] Preferably, the lower electrode layer is used to lead out a voltage signal of the thin film material, and the target material used includes aluminum-doped zinc oxide (AZO), indium tin oxide (ITO), copper, aluminum and platinum. The selection of the lower electrode material is based on the principle of forming an ohmic contact with undoped ZnS, ensuring the stability of current transmission, avoiding the interference of nonlinear effects, and ensuring the effective derivation of the piezoelectric signal.

[0013] More preferably, the lower electrode layer uses aluminum-doped zinc oxide as the target material, and when the lower electrode layer is prepared by the physical vapor deposition technology, the heating temperature of the substrate is 500 DEG C, and other deposition process parameters are the same as those for preparing the ZnS piezoelectric active layer.

[0014] Preferably, the rigid substrate includes a silicon wafer, quartz glass, a sapphire substrate and a hastelloy strip, and the flexible substrate includes polyethylene terephthalate plastic and polyimide plastic. A clean substrate is used as the basis for thin film growth, and the substrate covers rigid or flexible substrates to ensure the adhesion and uniformity of the thin film and improve the film quality.

[0015] The third aspect of the present application also provides an application of the zinc sulfide thin film material with longitudinal piezoelectric effect according to the first aspect, and the application field includes one-way precision sensing and quasi-static measurement.

[0016] Compared with the prior art, the present application has the following beneficial effects: The present application discloses a zinc sulfide (ZnS) thin film material with longitudinal piezoelectric effect and a preparation method thereof. The material uses undoped ZnS as a piezoelectric active material, and a lower electrode layer and a ZnS piezoelectric active layer are prepared on a rigid or flexible substrate in sequence by using a physical vapor deposition technology. By adjusting key process parameters such as deposition temperature, the ZnS thin film can form a fiber texture along the <111> crystal direction, only <111> characteristic diffraction peaks appear in the X-ray diffraction (XRD) spectrum, and the half-width of the corresponding rocking curve is less than 9 DEG.

[0017] The ZnS thin film material prepared by the present application has a piezoelectric coefficient d 33 which can reach 5-25 pm / V, the positive piezoelectric response presents linear and non-hysteresis characteristics, and the inverse piezoelectric hysteresis is caused by ion migration behavior; at the same time, the material has the advantages of low preparation cost, no environmental toxicity and good compatibility with semiconductor processes. The material successfully fills the technical gap of the longitudinal piezoelectric performance of zinc sulfide thin film, and is suitable for one-way precision sensing, quasi-static measurement and other application scenarios.

[0018] The core advantage of the present application is that, compared with existing lead-free piezoelectric thin films: (1) Controllable growth of fiber texture: for the first time, atomic-level directional construction of <111> single orientation fiber texture of ZnS thin film is realized, and the half-height width of the rocking curve is less than 9°, and the grains are arranged along the <111> direction, which provides the required macroscopic polarization axis for the development of the intrinsic piezoelectric effect of the material.

[0019] (2) High piezoelectric coefficient d 33 : Based on the strong ionicity of Zn-S bond and <111> orientation strain engineering, the intrinsic piezoelectric coefficient d 33 of the obtained ZnS thin film material reaches 5-25 pm / V. BRIEF DESCRIPTION OF DRAWINGS

[0020] Figure 1 is a structural schematic diagram of a ZnS double-layer thin film sample.

[0021] Figure 2 is a linear piezoelectric property curve of a ZnS double-layer thin film material.

[0022] Figure 3 is a high-resolution X-ray diffraction spectrum of a ZnS double-layer thin film material (different embodiments are represented by temperature).

[0023] Figure 4 is a rocking curve spectrum of a ZnS double-layer thin film material (different embodiments are represented by temperature).

[0024] Figure 5 is the vertical PFM measurement result of a ZnS double-layer thin film material (low-temperature sample) prepared in Example 1; wherein (a) is an amplitude mapping diagram, and (b) is a phase mapping diagram.

[0025] Figure 6 is the vertical PFM measurement result of a ZnS double-layer thin film material (high-temperature sample) prepared in Example 2; wherein (a) is an amplitude mapping diagram, and (b) is a phase mapping diagram.

[0026] Figure 7 is a displacement voltage schematic diagram of a ZnS double-layer thin film material; wherein (a) is a low-temperature sample of Example 1, and (b) is a high-temperature sample of Example 2.

[0027] Figure 8 is a linear piezoelectric response result of a ZnS double-layer thin film material; wherein (a) is a 200℃ sample of Example 1, (b) is a 400℃ sample of Example 3, (c) is a 600℃ sample of Example 4, and (d) is an 800℃ sample of Example 2. DETAILED DESCRIPTION

[0028] The specific embodiments of the present application are further described below. It is to be understood that the description of these embodiments is intended to help understand the present application and is not intended to limit the present application. Furthermore, the technical features involved in the various embodiments of the present application described below can be combined with each other as long as there is no conflict.

[0029] The experimental methods in the following examples are all conventional methods unless otherwise specified. The experimental materials used in the following examples are all commercially available unless otherwise specified.

[0030] Example 1: A preparation method of a zinc sulfide thin film material with longitudinal piezoelectric effect The zinc sulfide thin film material includes a ZnS piezoelectric active layer and a lower electrode layer stacked in sequence, and the preparation method is as follows: Using a pulsed laser deposition technology (using a PLD-450B type high vacuum pulsed laser sputtering thin film deposition system produced by Shenyang Scientific Instrument Company of Chinese Academy of Sciences (Shenyang Ke Yi)), a non-doped zinc sulfide ceramic target (4N pure zinc sulfide powder, cold isostatic pressing, sintering) is used as a deposition source to prepare a lower electrode layer on a quartz glass substrate after ultrasonic cleaning (to remove surface organic contaminants, inorganic particle impurities and adsorbed water), and then a non-doped ZnS thin film is prepared. The deposition process parameters are set as follows: First, the vacuum cavity is pumped to a background vacuum degree ≤5×10 -5 Pa, then the sample is sent into the cavity through the sample chamber; the distance between the substrate and the target material is controlled to be 60 mm; then the substrate is heated to 200°C and kept stable; then the laser energy is set to 200 mJ and the pulse frequency is set to 10 Hz. Through the above process, a high-quality 〈111〉 oriented ZnS thin film with a thickness of 90 nm can be prepared.

[0031] Among them, the preparation of the lower electrode selects aluminum-doped zinc oxide powder (AZO, cold isostatic pressing, sintering; as a target material, the deposition process parameters are set as follows: First, the vacuum cavity is pumped to a background vacuum degree ≤5×10 -5 Pa, then the sample is sent into the cavity through the sample chamber; the distance between the substrate and the target material is controlled to be 60 mm; then the substrate is heated to 500°C and kept stable; then the laser energy is set to 200 mJ and the pulse frequency is set to 10 Hz. Through the above process, a high-quality c-axis preferentially oriented (002) AZO thin film with a thickness of 110 nm can be prepared on the substrate.

[0032] After the preparation of the double-layer thin film ( Figure 1 ), structural characterization and piezoelectric property testing are carried out (using a triangular wave pressure signal as a test excitation, such as Figure 2The excitation test is a linear triangular wave, as shown, to verify the linear output characteristics of the ZnS material. High-resolution X-ray diffraction (2θ-ω scan) shows that only a characteristic diffraction peak attributed to the (111) crystal plane appears at 28.4° in the diffraction pattern of the ZnS film, confirming that the ZnS film has a single <111> out-of-plane preferred orientation; the remaining diffraction peaks correspond to the (002) crystal plane diffraction of the AZO electrode (as shown in FIG. 2). Figure 3 To further evaluate the crystal quality of the ZnS film along the <111> crystal direction, ω-scan test was carried out. The test results show that the full width at half maximum (FWHM) of the <111> crystal direction diffraction peak is less than 9° (as shown in FIG. 3). Figure 4

[0033] The piezoelectric performance of the ZnS film was characterized by piezoelectric force microscopy (PFM), and the results showed that the piezoelectric response of the film was uniform; the phase diagram confirmed that it did not have reversible piezoelectric domains and did not have ferroelectric characteristics (as shown in FIG. 5).

[0034] The vertical displacement-voltage (D-V) quasi-static hysteresis loop test was carried out on the film, and 10 cyclic scans were carried out within a voltage range of ±10 V. Due to the ion migration phenomenon, the test curve showed a ferroelectric butterfly-shaped feature (as shown in FIG. 6a). Figure 7 Through data fitting calculation, the piezoelectric voltage constant d 33 of the film was about 6.63 pm / V, confirming that the film had linear positive piezoelectric characteristics.

[0035] The reverse piezoelectric effect test results showed that when a linearly varying pressure load was applied, the film output showed a linearly varying electric signal (as shown in FIG. 6b). Figure 8 The above test results fully prove that the <111> preferred orientation ZnS film has stable linear inverse piezoelectric characteristics and can meet the application requirements of high-precision pressure sensing scenarios.

[0036] Example 2: The preparation method is basically the same as that of Example 1, except that the substrate heating temperature during deposition is kept at 800°C. This example also obtains high-quality <111> oriented ZnS film.

[0037] After the preparation of the double-layer film, structure characterization and piezoelectric performance test were carried out: High-resolution X-ray diffraction (2θ-ω scan) shows that only a characteristic diffraction peak attributed to the (111) crystal plane appears at 28.4° in the diffraction pattern of the ZnS film, confirming that the ZnS film has a single <111> out-of-plane preferred orientation; the remaining diffraction peaks correspond to the (002) crystal plane diffraction of the AZO electrode (as shown in FIG. 2). Figure 3 ​The ω-scan test results show that the full width at half maximum (FWHM) of the <111> orientation diffraction peak of the ZnS film is still less than 9°, indicating that the excellent crystalline quality is not deteriorated (as shown in FIG. 8a). Figure 4

[0038] The piezoelectric force microscope (PFM) test results show that the 180° phase inversion partition appears in the phase diagram of the film, and the amplitude signals of different regions are significantly different (as shown in FIG. 8b). Figure 6

[0039] The vertical displacement-voltage (D-V) hysteresis test shows that the hysteresis loop is butterfly-shaped (as shown in FIG. 8c). Figure 7 The hysteresis phenomenon is caused by the ion migration process under the electric field driving, rather than the intrinsic ferroelectricity of the material; the hysteresis loops are well overlapped in multiple cycle tests, and the piezoelectric voltage constant d33 of the film is calculated to be about 25 pm / V through data fitting. d33

[0040] The reverse piezoelectric effect test results show that the film can still output linearly changing electric signals under the action of pressure load (as shown in FIG. 8d), maintaining the stable linear reverse piezoelectric response characteristics. Figure 8

[0041] Example 3: The preparation method is basically the same as that of Example 1, except that the substrate heating temperature during the deposition process is kept at 400°C. This example also obtains high-quality <111> oriented ZnS film, and the piezoelectric characteristics thereof are consistent with those of Example 1 (as shown in FIGS. 8e, Figure 3 , 4 ,8b).

[0042] Example 4: The preparation method is basically the same as that of Example 1, except that the substrate heating temperature during the deposition process is kept at 600°C. This example also obtains high-quality <111> oriented ZnS film, and the piezoelectric characteristics thereof are consistent with those of Example 1 (as shown in FIGS. 8f, Figure 3 , 4 ,8c).

[0043] The embodiments of the present application are described in detail above, but the present application is not limited to the described embodiments. For those skilled in the art, various changes, modifications, replacements and variations of the embodiments are made without departing from the principles and spirits of the present application, and still fall within the protection scope of the present application.​​

Claims

1. A zinc sulfide thin film material with longitudinal piezoelectric effect, characterized in that, The zinc sulfide thin film material comprises a ZnS piezoelectric active layer and a lower electrode layer stacked sequentially, wherein the ZnS piezoelectric active layer has a axial direction. <111> Fiber texture of crystal orientation and d 33 It exhibits piezoelectric response characteristics, with its positive piezoelectric effect being linear and hysteretic, while its inverse piezoelectric response exhibits hysteresis caused by ion migration.

2. The zinc sulfide thin film material with longitudinal piezoelectric effect according to claim 1, characterized in that, The XRD pattern of the ZnS piezoelectric active layer shows only ZnS. <111> The diffraction peak has a half-width at half-maximum (FWHM) of less than 9°.

3. The zinc sulfide thin film material with longitudinal piezoelectric effect according to claim 1, characterized in that, The ZnS piezoelectric active layer d 33 The value is 5-25 pm / V.

4. The method for preparing the zinc sulfide thin film material with longitudinal piezoelectric effect according to any one of claims 1-3, characterized in that, Using undoped ZnS as the piezoelectric active material, a ZnS piezoelectric active layer is prepared on a rigid or flexible substrate using physical vapor deposition technology, and then a lower electrode layer is prepared to obtain a zinc sulfide thin film material with longitudinal piezoelectric effect. Before deposition, the vacuum chamber is evacuated to a background vacuum level of ≤5×10⁻⁶. -5 Pa, the distance between the substrate and the target is controlled to be 50-70 mm; During the deposition process, the substrate heating temperature is maintained at 200-800℃, the laser energy is set to 150-300 mJ, and the pulse frequency is 7-15Hz.

5. The method for preparing zinc sulfide thin film material with longitudinal piezoelectric effect according to claim 4, characterized in that, Before deposition, the vacuum chamber is evacuated to a background vacuum level of ≤5×10⁻⁶. -5 Pa, the distance between the substrate and the target is controlled at 60 mm; during the deposition process, the substrate heating temperature is maintained at 200-800℃, the laser energy is set to 200 mJ, and the pulse frequency is 20 Hz.

6. The method for preparing zinc sulfide thin film material with longitudinal piezoelectric effect according to claim 4, characterized in that, The lower electrode layer is used to extract voltage signals from the thin film material, and the target materials used include aluminum-doped zinc oxide, indium tin oxide, copper, aluminum, and platinum.

7. The method for preparing zinc sulfide thin film material with longitudinal piezoelectric effect according to claim 6, characterized in that, The target material used for the lower electrode layer is aluminum-doped zinc oxide. When the lower electrode layer is prepared using physical vapor deposition technology, the heating temperature of the substrate is 500℃.

8. The method for preparing zinc sulfide thin film material with longitudinal piezoelectric effect according to claim 4, characterized in that, The rigid substrate includes silicon wafers, quartz glass, sapphire substrates, and Hastelloy strips, while the flexible substrate includes polyethylene terephthalate plastic and polyimide plastic.

9. The application of the zinc sulfide thin film material with longitudinal piezoelectric effect according to any one of claims 1-3, characterized in that, Applications include unidirectional precision sensing and quasi-static measurement.

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