Novel linear piezoelectric response film material and preparation method thereof
The <111> orientation nickel oxide film was prepared by pulsed laser sputtering deposition method, which solved the problem that the central symmetric crystal did not have piezoelectricity, realized linear piezoelectric characteristics, and expanded the application range of piezoelectric materials.
Patent Information
- Application Number
- CN202510307640.5
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-03-17
- Publication Date
- 2025-06-17
AI Technical Summary
Traditional concepts believe that central symmetric crystals do not have piezoelectric properties, which limits the scope of exploration of piezoelectric materials. Especially as an important P-type semiconductor, NiO has a rock-salt-type structure that is considered not piezoelectric.
The nickel oxide (NiO) film with <111> orientation was prepared by pulsed laser sputtering deposition method, breaking the traditional orientation limitations of piezoelectric materials and realizing the linear piezoelectric characteristics of the central symmetric crystal.
A nickel oxide film with a centrally symmetric rock salt structure, an orientation and exhibiting linear piezoelectric characteristics was successfully prepared, breaking through the limitations of traditional piezoelectric materials and has broad application prospects in the fields of sensors, microelectromechanical systems, electronic and optoelectronic devices and medical care.
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Figure CN120166909A_ABST
Abstract
Description
Technical Field
[0001] The present invention relates to the technical field of the preparation of piezoelectric response thin film materials, and particularly relates to a novel linear piezoelectric response thin film material and a preparation method thereof. Background Art
[0002] For a long time, the piezoelectric effect has been recognized as the polarization of piezoelectric materials when subjected to external stress, and the degree of polarization is proportional to the applied stress. The traditional concept holds that the piezoelectric effect can only be observed in non-centrosymmetric crystals, while centrosymmetric crystals are considered to have no piezoelectricity, which greatly limits the scope of exploration of piezoelectric materials.
[0003] As an important P-type semiconductor, NiO has been widely and deeply studied due to its potential application value in many fields such as photocatalysis, supercapacitors, lithium-ion batteries, magnetic materials, non-volatile memories, etc. NiO with a rock-salt structure has a center of symmetry. According to the existing piezoelectric theory, NiO is considered to have no piezoelectricity. In the methods for preparing NiO thin films, there are currently various means, such as molecular beam epitaxy (MBE), magnetron sputtering, chemical vapor deposition (CVD), pulsed laser deposition (PLD), spray pyrolysis, electron beam evaporation, sol-gel method, etc. Among them, the pulsed laser sputtering deposition method has advantages such as high atomic beam current energy, low working vacuum degree, and low substrate temperature requirement compared with other thin film preparation methods. Through the pulsed laser sputtering deposition method, <111>-oriented NiO thin films can be obtained. This achievement breaks the traditional limitation that only non-centrosymmetric crystal materials can be used as piezoelectric materials, and the thin films have linear piezoelectric characteristics.
[0004] Based on the above research background, the present invention is committed to realizing the preparation of <111>-oriented NiO thin films of novel piezoelectric materials. The preparation of this linear piezoelectric characteristic NiO thin film is of great significance for the research of novel piezoelectric materials, and also has broad application prospects in the fields of sensors, microelectromechanical systems, electronic and optoelectronic devices, medical fields, etc.
[0005] Therefore, according to the relevant technologies described above, it is urgent to develop a novel linear piezoelectric response thin film material and a preparation method thereof. Summary of the Invention
[0006] In view of this, the purpose of the present invention is to provide a novel linear piezoelectric response thin film material and a preparation method thereof, aiming to provide a novel linear piezoelectric response thin film material and a preparation method thereof. The NiO material used is a thin film material with a centrosymmetric crystal structure and grown along the <111> crystal orientation, which can exhibit excellent linear piezoelectric characteristics and breaks through the existing limitation that only non-centrosymmetric crystal materials can be used as piezoelectric materials.
[0007] For the above purposes, the present invention provides a novel linear piezoelectric response thin film material and a preparation method thereof.
[0008] A novel linear piezoelectric response thin film material, the thin film material being nickel oxide, the crystal structure of the nickel oxide being a rock salt structure, and the nickel oxide piezoelectric thin film having a unique orientation along the <111> direction.
[0009] A preparation method of a novel linear piezoelectric response thin film material, comprising the following steps:
[0010] Step S1. Prepare a substrate: ultrasonically clean the substrate to obtain a clean substrate, select a target, adjust the distance between the substrate and the target, and heat the substrate to 400 °C in a pressure atmosphere of 5×10 -5 Pa, and coat the film for 10 min at an energy of 150 mJ and a frequency of 10 Hz to obtain an upper electrode thin film and a lower electrode thin film with a thickness of 250 nm each, thereby obtaining a substrate.
[0011] Step S2. Select a high-purity target, adjust the distance between the high-purity target and the substrate, and heat the substrate to 400 °C in a pressure atmosphere of 5×10 -5 Pa, and coat the film for 10 min at an energy of 150 mJ and a frequency of 16 Hz to obtain a <111>-oriented nickel oxide piezoelectric thin film with a thickness of 150 nm.
[0012] Preferably, in step S1, the target is a zinc oxide target with 2% alumina by weight; the distance between the substrate and the target in step S1 is 60 mm.
[0013] Preferably, in step S2, the high-purity target is a nickel oxide target with a purity > 99.99%; the distance between the high-purity target and the substrate in step S2 is 60 mm.
[0014] Preferably, the substrate is any one of a rigid substrate and a flexible substrate.
[0015] Preferably, the rigid substrate is any one of a silicon wafer, glass, and a sapphire substrate.
[0016] Preferably, the material of the flexible substrate is any one of polyethylene terephthalate plastic, polyimide plastic, and Hastelloy strip.
[0017] Preferably, the lower electrode thin film is used to lead out the voltage signal of the thin film material and serves as a buffer layer for the preparation of the piezoelectric active material layer, and the material of the lower electrode thin film is any one of aluminum-doped zinc oxide, indium tin oxide, copper, aluminum, and platinum.
[0018] Preferably, the coating method of the nickel oxide piezoelectric thin film on the upper surface of the lower electrode thin film is any one of pulsed laser deposition, magnetron sputtering, chemical vapor deposition, sol-gel spin coating method, hydrothermal self-assembly method, and liquid phase cooling method.
[0019] Advantages of the present invention:
[0020] By selecting a clean substrate, covering both rigid substrates and flexible substrates, the present invention ensures the film adhesion and uniformity, and improves the overall performance; carefully selects the lower electrode material to form an ohmic contact with undoped nickel oxide, ensuring stable current transmission and precise conduction of piezoelectric response; precisely controls the preparation process and coating process of the lower electrode, promoting the formation of <111> out-of-plane crystal orientation of the nickel oxide thin film, constructing a stable chemical interface, and improving the stability and consistency of piezoelectric performance; uses undoped nickel oxide as the piezoelectric material, precisely controls the oxygen vacancy concentration, reduces defects, enhances the orderliness of the crystal structure, and improves the piezoelectric response; uses triangular wave pressure signal input testing to verify the linear output characteristics of the nickel oxide material. Compared with the prior art, a nickel oxide thin film with a centrosymmetric rock salt structure, <111> orientation and exhibiting linear piezoelectric characteristics is successfully prepared, breaking through the limitations of traditional piezoelectric materials, and having broad application prospects in the fields of sensors, microelectromechanical systems, electronics, optoelectronic devices, and medical treatment. Description of the drawings
[0021] In order to more clearly illustrate the technical solutions in the present invention or the prior art, the following will briefly introduce the drawings required for use in the description of the embodiments or the prior art. Obviously, the drawings in the following description are only those of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can also be obtained based on these drawings.
[0022] Figure 1 It is a sample schematic diagram of the novel linear piezoelectric response NiO thin film material which is the main body of the present invention;
[0023] Figure 2 It is a schematic diagram of the linear piezoelectric characteristic curve of the novel linear piezoelectric response NiO thin film material which is the main body of the present invention;
[0024] Figure 3 It is a high-resolution X-ray color map of the NiO thin film material with Hastelloy as the substrate using the pulsed laser sputtering method;
[0025] Figure 4 It is the XPS full spectrum of the novel linear piezoelectric response NiO thin film material which is the main body of the present invention;
[0026] Figure 5 It is the XPS fine spectrum of the novel linear piezoelectric response NiO thin film material which is the main body of the present invention;
[0027] Figure 6 Vertical PFM measurement height of the novel linear piezoelectric response NiO thin film material of the main body of the present invention;
[0028] Figure 7 Vertical PFM measurement amplitude of the novel linear piezoelectric response NiO thin film material of the main body of the present invention;
[0029] Figure 8 Vertical PFM phase mapping of the novel linear piezoelectric response NiO thin film material of the main body of the present invention;
[0030] Figure 9 Displacement voltage schematic diagram of the novel linear piezoelectric response NiO thin film material of the main body of the present invention;
[0031] Figure 10 Phase voltage loop schematic diagram of the novel linear piezoelectric response NiO thin film material of the main body of the present invention;
[0032] Figure 11 Schematic diagram of the linear piezoelectric response of the novel linear piezoelectric response NiO thin film material with a silicon wafer as the substrate of the main body of the present invention. Detailed implementation manners
[0033] To make the objectives, technical solutions and advantages of the present invention clearer and more understandable, the present invention will be further described in detail below in conjunction with specific embodiments.
[0034] Embodiment 1: A preparation method of a novel linear piezoelectric response thin film material, comprising the following steps:.
[0035] S1. Ultrasonically clean the Hastelloy baseband to obtain a clean Hastelloy baseband;
[0036] S2. Select a zinc oxide target with 2% alumina by weight, adjust the distance between the Hastelloy baseband and the target to 60 mm, evacuate the coating chamber of the pulsed laser sputtering equipment to below 5×10 -5 Pa, heat the Hastelloy baseband to 400 °C, turn on the pulsed laser, with a laser energy of 150 mJ and a pulse frequency of 10 Hz, and coat for 10 min to obtain upper and lower electrode thin films with a thickness of 250 nm each, that is, obtain the Hastelloy coated with aluminum-doped zinc oxide;
[0037] S3. Use the Hastelloy coated with aluminum-doped zinc oxide as the substrate wafer, use a high-purity nickel oxide target with a purity > 99.99%, adjust the distance between the substrate wafer and the target to 60 mm, evacuate the coating chamber to 5×10 -5Below Pa, the substrate wafer was heated to 400 °C, the pulsed laser was turned on, the laser energy was 150 mJ, the pulse frequency was 16 Hz, and the film was coated for 10 min. Finally, a <111>-oriented nickel oxide film with a thickness of 150 nm was obtained; the obtained nickel oxide piezoelectric film had a unique preferred orientation along the <111> direction;
[0038] S4. XRD test: The sample and the substrate were subjected to 2θ-ω scanning by a high-resolution X-ray diffractometer (HRXRD), and the results were as Figure 3 shown. The obtained NiO film had a unique diffraction peak <111>, and its two-fold Bragg diffraction angle 2θ was 32.6°, indicating that it had a unique out-of-plane crystal orientation NiO<111>. The remaining diffraction peaks were the diffraction peaks of the Hastelloy substrate used, the diffraction peak of the cerium oxide buffer layer CeO2<002>, and the diffraction peak of the aluminum-doped zinc oxide electrode AZO<002>. Since the in-plane structure of the AZO(002) plane was hexagonal symmetric and matched the hexagonal symmetric structure of the NiO(111) crystal plane;
[0039] S5. XPS test: The NiO film was scanned by X-ray photoelectron spectroscopy, and the full-spectrum results were as Figure 4 shown, confirming the presence of Ni and O elements. The results of its fine spectrum were as Figure 5 shown, and the measured internal atomic ratio was Ni:O = 47.19:52.81. The test results detected the presence of trivalent nickel, indicating the presence of nickel vacancies in the material, which in turn led to a decrease in nickel content. During the growth of the material, nickel vacancies played a key role in balancing the spontaneous polarization. When the material was subjected to external stress, its polarization degree changed, and in order to re-establish equilibrium, an induced voltage would be generated inside the material. Therefore, in the piezoelectric nickel oxide film, the regulation of nickel vacancies was of great significance for optimizing its performance;
[0040] S6. PFM test: The surface morphology of the NiO film was tested by piezoresponse force microscopy (PFM), and the results were as Figure 6 shown, and its roughness Rq was about 1.3 nm. Figure 7 The PFM amplitude map of the NiO film shown indicated that the piezoelectric response of the film was relatively uniform. Combining with Figure 8 the phase diagram shown, it could be seen that there were no reversible piezoelectric domains in the sample and it did not have ferroelectric properties.
[0041] S7. PFM displacement voltage and phase voltage test: Figure 9 and Figure 10The results of the vertical PFM displacement voltage (D-V) and phase voltage (P-V) loops shown indicate that when a quasi-static voltage of ±10 V is input, the piezoelectric displacement response within 10 cycles of testing is basically linear, while the piezoelectric response phase undergoes a 180° inversion with the reversal of the voltage polarity. This shows that the <111>-oriented nickel oxide thin film in this embodiment exhibits linear direct piezoelectric characteristics. By linearly fitting the D-V curve, the piezoelectric coefficient d 33 of the NiO thin film is approximately 5.84 ± 0.82 pm / V.
[0042] S8. Test of converse piezoelectric characteristics: The test results of the converse piezoelectric characteristics of the <111>-oriented nickel oxide thin film in this embodiment are as Figure 11 shown. After applying a linearly varying pressure, the thin film outputs a linearly varying voltage, indicating that the <111>-oriented nickel oxide thin film in this embodiment exhibits linear converse piezoelectric characteristics. At the same time, the test results prove that the <111>-oriented nickel oxide thin film in this embodiment can be applied to high-precision pressure sensors.
[0043] Example 2:
[0044] Use other substrates that meet the following conditions: 1. The substrate material should have good chemical stability; 2. The substrate surface should have appropriate roughness; 3. It is possible to obtain an out-of-plane <111>-oriented thin film; 4. The electrode layer has high conductivity and forms an ohmic contact at the interface.
[0045] For example, use a polished silicon wafer cleaned by ultrasonic waves as the substrate, aluminum-doped zinc oxide as the upper and lower electrodes, and adopt the thin film preparation process in Example 1. Under these conditions, a high-quality undoped <111>-oriented nickel oxide thin film is obtained. It exhibits linear direct and converse piezoelectric characteristics, and the piezoelectric coefficient ranges from 5 to 20 pm / V.
[0046] Example 3:
[0047] When using different nickel oxide thin film preparation processes, the following conditions should be met: 1. The out-of-plane crystal orientation of the nickel oxide thin film remains <111>; 2. The defects of the nickel oxide thin film are properly controlled and there should be no leakage; 3. The nickel oxide thin film forms an ohmic contact with the upper and lower electrodes; 4. The resistivity in the nickel oxide thin film is above 1000 ohm-cm.
[0048] For example, use Hastelloy cleaned by ultrasonic waves as the substrate, aluminum-doped zinc oxide as the upper and lower electrodes. When preparing the nickel oxide thin film, the substrate heating temperature is 500 °C, and other process conditions and preparation conditions are the same as in Example 1. Under these conditions, a high-quality undoped <111>-oriented nickel oxide thin film is obtained. Its crystal structure is a rock salt structure with a center symmetry point, and it exhibits linear direct and converse piezoelectric characteristics, and the piezoelectric coefficient ranges from 5 to 20 pm / V.
[0049] Comparative Example 1:
[0050] When the out-of-plane orientation of the obtained nickel oxide thin film is not <111>, there is no normal polarity and piezoelectric response.
[0051] For example, when using metallic aluminum as the upper and lower electrodes, a high-purity (>4N) aluminum target, a Hastelloy alloy baseband after ultrasonic cleaning as the substrate, adjusting the substrate-target distance to 60 mm, evacuating the coating chamber of the pulsed laser sputtering equipment to below 5E-5 Pa, heating the substrate to a high temperature of 300 °C, turning on the pulsed laser, with a laser energy of 150 mJ, a pulse frequency of 10 Hz, coating for 10 min, upper and lower aluminum material electrode thin films with a thickness of about 300 nm are obtained. The nickel oxide coating uses the preparation process in Example 1, and other parameters are the same as those in Example 1. The nickel oxide thin film obtained at this time has a <002> orientation and does not have piezoelectric properties.
[0052] Data analysis:
[0053] Example 1: Through testing with a high-resolution X-ray diffractometer (HRXRD), the NiO thin film presents a unique diffraction peak 111, and the two-fold Bragg diffraction angle 2θ is 32.6°, determining its unique out-of-plane crystal orientation NiO<111>; X-ray photoelectron spectroscopy testing confirms the existence of Ni and O elements, with an internal atomic ratio of Ni:O = 47.19:52.81, and trivalent nickel is detected, indicating the existence of nickel vacancies; piezoresponse force microscopy (PFM) testing shows that the film roughness Rq is about 1.3 nm, the piezoelectric response is uniform, there are no reversible piezoelectric domains, and it does not have ferroelectric properties; PFM displacement voltage (D-V) and phase voltage (P-V) loop testing show that when applying ±10 V quasi-static voltage, the piezoelectric displacement response is basically linear within 10 cycles, and the piezoelectric coefficient d33 is about 5.84 ± 0.82 pm / V. Reverse piezoelectric property testing shows that when applying a linear pressure, the film outputs a linear voltage, which can be applied to high-precision pressure sensors; Example 2: Using a polished silicon wafer that meets specific conditions as the substrate, and applying the process of Example 1, a high-quality undoped <111>-oriented nickel oxide thin film is successfully obtained, showing linear forward and reverse piezoelectric properties, with a piezoelectric coefficient range of 5 - 20 pm / V; Example 3: Changing the preparation process of the nickel oxide thin film to meet specific conditions, a high-quality undoped <111>-oriented nickel oxide thin film is also obtained, having a centrosymmetric rock salt structure, showing linear forward and reverse piezoelectric properties, with a piezoelectric coefficient range of 5 - 20 pm / V; Comparative Example 1: When the out-of-plane orientation of the nickel oxide thin film is <002>, it does not have piezoelectric properties, highlighting the key role of the <111> orientation in piezoelectric performance.
[0054] Those of ordinary skill in the art should understand that any discussion of the above embodiments is merely exemplary and is not intended to imply that the scope of the present invention is limited to these examples; under the concept of the present invention, the technical features in the above embodiments or different embodiments can also be combined, the steps can be implemented in any order, and there are many other variations in different aspects of the present invention as described above, which are not provided in detail for the sake of brevity.
[0055] The present invention is intended to cover all such substitutions, modifications, and variations that fall within the broad scope of the appended claims. Therefore, any omissions, modifications, equivalent substitutions, 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 novel linear piezoelectric response film material, characterized in that: The film material is nickel oxide, the crystal structure of the nickel oxide is a rock salt structure, and the nickel oxide piezoelectric film has a <111> The only orientation of the direction.
2. A method for preparing a novel linear piezoelectric response thin film material, characterized in that: The following steps are involved: Step S1. Prepare the substrate: ultrasonically clean the substrate to obtain a clean substrate, select the target material, adjust the distance between the substrate and the target material, and -5 The substrate was heated to 400°C in a pressure atmosphere of 1.5 Pa, and film-coated for 10 min at an energy of 150 mJ and a frequency of 10 Hz to obtain an upper electrode film and a lower electrode film with a thickness of 250 nm, thereby obtaining a substrate substrate; Step S2. Select a high-purity target material and adjust the distance between the high-purity target material and the substrate to 5×10 -5 The substrate was heated to 400°C in a pressure atmosphere of 1.5 Pa, and the film was deposited for 10 min at an energy of 150 mJ and a frequency of 16 Hz to obtain a 150 nm thick film. <111> Oriented nickel oxide piezoelectric film.
3. The method for preparing the novel linear piezoelectric response thin film material according to claim 2, characterized in that: The target material in step S1 is a zinc oxide target material with a weight ratio of 2% aluminum oxide; the distance between the substrate and the target material in step S1 is 60 mm.
4. The method for preparing the novel linear piezoelectric response thin film material according to claim 2, characterized in that: The high-purity target material in step S2 is a nickel oxide target material with a purity greater than 99.99%; the distance between the high-purity target material and the substrate in step S2 is 60 mm.
5. The method for preparing the novel linear piezoelectric response thin film material according to claim 2, characterized in that: The substrate base sheet is any one of a rigid substrate and a flexible substrate.
6. The method for preparing the novel linear piezoelectric response thin film material according to claim 5, characterized in that: The rigid substrate is any one of a silicon wafer, a glass and a sapphire substrate.
7. The method for preparing the novel linear piezoelectric response thin film material according to claim 5, characterized in that: The material of the flexible substrate is any one of polyethylene terephthalate plastic, polyimide plastic and Hastelloy strip.
8. The method for preparing the novel linear piezoelectric response thin film material according to claim 2, characterized in that: The material of the lower electrode film is any one of aluminum-doped zinc oxide, indium tin oxide, copper, aluminum and platinum.
9. The method for preparing the novel linear piezoelectric response thin film material according to claim 2, characterized in that: The coating method of the nickel oxide piezoelectric film on the upper surface of the lower electrode film is any one of pulsed laser deposition, magnetron sputtering, chemical vapor deposition, sol-gel spin coating, hydrothermal self-assembly and liquid phase cooling.