Ultra-flat multi-waveform high-V-doped LiNbO3 film sensor and preparation method thereof

Abstract

The invention discloses an ultra-flat multi-waveform high-V-doped LiNbO3 thin film sensor and a preparation method thereof, and the preparation method comprises the following steps: preparing the high-V-doped LiNbO3 thin film sensor on the surface of a base material through a magnetron sputtering method by adopting a LiNbO3 target material with the V-doped atom number accounting for 4%-14%; the preparation method of the LiNbO3 target material comprises the following steps: soaking lithium nitrate, ammonium niobium oxalate and amino acid in a nitrate solution to form a viscous precursor, and carrying out heat treatment on the viscous precursor to obtain nanoscale LiNbO3 powder; the preparation method comprises the following steps: dispersing nanoscale LiNbO3 powder in a composite solvent, introducing a V source to form gel, and carrying out heat treatment on the gel to obtain nanoscale high-V-doped LiNbO3 powder; and the nanoscale high-V-doped LiNbO3 powder is pressed to obtain the LiNbO3 target material with the V-doped atom number accounting for 4%-14%. The high-vanadium-doped LiNbO3 thin film sensor prepared by the invention has excellent piezoelectric property, extremely strong ultrasonic signals and very smooth and flat surface and section morphology.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of LiNbO3 piezoelectric material and sensor, and particularly relates to an ultra-flat multi-wave high-V doped LiNbO3 thin film sensor and a preparation method thereof. BACKGROUND

[0002] LiNbO3 is a ferroelectric body of trigonal system, which has good piezoelectric effect, relatively wide working temperature range and good chemical stability, and has wide application in the direction of piezoelectric sensor. The LiNbO3 piezoelectric coating (thin film) is the most important component part of the piezoelectric sensor, and the ability of generating ultrasonic waves mainly depends on its piezoelectric constant d 33 At present, through the magnetron sputtering technology, the LiNbO3 piezoelectric coating can be deposited on the surface of the fastener, so as to realize the in-situ monitoring of stress and temperature in the service life of the fastener. Designing high-performance LiNbO3 target is the premise of improving the performance of the piezoelectric sensor.

[0003] Some studies, such as CN119144932A, disclose a high piezoelectric performance vanadium-doped LiNbO3 piezoelectric coating and a preparation method thereof. A vanadium-doped lithium niobate target with a vanadium doping atomic number ratio of 2.4%-3.9% is used to prepare a vanadium-doped LiNbO3 piezoelectric coating without impurity phase and with an O / Nb atomic ratio close to the ideal state. Compared with the piezoelectric coating without vanadium doping, the piezoelectric signal of the piezoelectric coating is significantly improved. However, the piezoelectric coating prepared by the vanadium-doped lithium niobate target with a vanadium doping of 4.0% does not have piezoelectric performance, and the piezoelectric signal still has a large space for improvement.

[0004] Therefore, it is necessary to design and improve the existing target to prepare a LiNbO3 thin film sensor with better performance to meet the detection needs in more scenes. SUMMARY

[0005] The purpose of the present application is to design and improve the preparation method of the existing LiNbO3 target, introduce higher V content, and obtain a V-doped LiNbO3 thin film sensor with specific preferred crystal face orientation, smooth and flat surface, and excellent ultrasonic performance.

[0006] In order to achieve the above purpose, the present application provides a preparation method of an ultra-flat multi-wave high-V doped LiNbO3 thin film sensor, comprising, adopting a LiNbO3 target with a V doping atomic number ratio of 4%-14% and an electrode target, and preparing an ultra-flat multi-wave high-V doped LiNbO3 piezoelectric coating and an electrode layer on the surface of a substrate in sequence by a magnetron sputtering method; The preparation method of the LiNbO3 target comprises, Lithium nitrate, niobium ammonium oxalate hydrate, and amino acids were soaked in a nitrate solution to form a viscous precursor. The viscous precursor was then heat-treated to obtain nano-sized LiNbO3 powder. Nanoscale LiNbO3 powder was dispersed in a composite solvent and then introduced into a V source to form a gel. The gel was then heat-treated to obtain nanoscale high V-doped LiNbO3 powder. The nanoscale highly V-doped LiNbO3 powder was pressed to obtain LiNbO3 targets with a V-doping atomic ratio of 4%-14%.

[0007] Furthermore, the molar ratio of lithium nitrate, niobium ammonium oxalate, and amino acids is 1:1:0.5-2; The concentration of the nitrate solution is 0.2-0.5 mol / L.

[0008] The nitrate solution is preferably an ammonium nitrate solution.

[0009] The volume of the nitrate solution containing lithium nitrate, niobium ammonium oxalate, and amino acids does not need to be strictly limited, as long as it can ensure good dispersion and normal gel formation.

[0010] Furthermore, the composite solvent is prepared by mixing ethylene glycol, water, and acetic acid in a volume ratio of 0.5-1.5:1:0.5-1.5.

[0011] The volume of the composite solvent used to disperse nano-sized LiNbO3 powder does not need to be strictly limited, as long as it can ensure good dispersion of the nano-sized LiNbO3 powder. The amount of V source added is determined according to the number of Nb atoms doped in the finished LiNbO3 target.

[0012] Furthermore, the heat treatment is carried out at 500-900℃ for 0.5-2 hours.

[0013] Furthermore, the size of the nanoscale LiNbO3 powder and the nanoscale high-V doped LiNbO3 powder is 80-150 nm.

[0014] Furthermore, the V source need not be strictly limited, and the valence state of V in the V source is +5. For example, it can be at least one of VO(OC2H5)3, NH4VO3, etc.

[0015] Furthermore, the density of the V-doped LiNbO3 target is between 4.61 and 4.63 g / cm³. 3 .

[0016] V is in a high-price state (such as V) 5+ ) Replace Nb 5+Since the atomic weight of V (50.94) is slightly lower than that of Nb (92.91), the density of the target material is slightly reduced after doping. This invention facilitates the preparation of high-density V-doped LiNbO3 targets by synthesizing nanoscale LiNbO3 powder and nanoscale V-doped LiNbO3 powder in sequence, so that the density difference between the V-doped LiNbO3 target and the pure LiNbO3 target is less than 0.7%.

[0017] Furthermore, the specific magnetron sputtering parameters for preparing ultraflat, multi-waveform, high-V-doped LiNbO3 piezoelectric coatings include: The experiment was conducted under Ar and O2 atmospheres, with a total flow rate of 0.6-0.9 Pa. The radio frequency power was controlled at 800-900 W, the temperature at 150-250 °C, the target distance at 4-5.5 cm, the radial distance at 0-6 cm, and the time at 2-8 h.

[0018] Furthermore, during magnetron sputtering, the introduced volumes of Ar and O2 gases are controlled, with a volume ratio of Ar to O2 of 6.1-8.3:1.

[0019] Furthermore, a bias voltage of -34V to -7V is set between the target and the substrate during magnetron sputtering.

[0020] Furthermore, the specific magnetron sputtering parameters for preparing the electrode layer include: Using 99.99% high-purity Ti target material, pure Ar gas is introduced at a flow rate of 0.6-1.2 Pa, and the RF power is controlled at 500-800W, the temperature at 50-150℃, the target-substrate distance at 7-10cm, the radial distance at 0-6cm, and the time at 2-5h.

[0021] In magnetron sputtering, the target-substrate distance refers to the lateral distance between the center of the target and the center of the substrate; the radial distance refers to the longitudinal distance between the substrate and the center of the target and the center of the substrate when they coincide. The radial distance is not directional, and when the longitudinal distance is 0, the center of the target and the center of the substrate coincide.

[0022] It should be noted that in this invention, the type and material of the substrate are not strictly limited. For example, it can be a silicon wafer, stainless steel plate, bolt, or other types of fasteners. Before magnetron sputtering, the substrate is also subjected to conventional pretreatment methods in the art, such as grinding and cleaning, to enhance the adhesion performance of the coating.

[0023] The present invention also provides an ultraflat, multi-waveform, high-V-doped LiNbO3 thin film sensor, which is prepared by the above-described method.

[0024] Compared with the prior art, the present invention has the following beneficial effects: 1. This invention provides a method for preparing a high-density, high-doped V-doped lithium niobate target. By sequentially synthesizing nanoscale LiNbO3 powder and nanoscale V-doped LiNbO3 powder, it is beneficial to prepare a high-density V-doped lithium niobate target, so that the density difference between the V-doped lithium niobate target and the pure lithium niobate target is less than 0.7%, thereby preparing a uniformly doped, high-density, ultra-smooth and flat V-doped LiNbO3 thin film sensor.

[0025] 2. The high-V doped LiNbO3 piezoelectric coating prepared by the present invention has a very smooth and flat surface and cross-sectional morphology, with a surface roughness as low as 7.5 nm, a novel crystal structure, a (110) preferred orientation, and no impurity phases such as NbO, Nb2O5, and LiNb3O8. The O / Nb atomic ratio reaches 2.9, which is close to the ideal morphology.

[0026] 3. The high-V doped LiNbO3 thin film sensor prepared by this invention exhibits excellent piezoelectric properties, with a piezoelectric constant d0. 33 The performance was significantly improved, reaching 23.1 pC / N, which is 3.8 times that of pure lithium niobate crystals and 7.7 times that of pure LiNbO3 thin film sensors prepared under the same experimental conditions.

[0027] 4. The high-V doped LiNbO3 thin film sensor prepared by this invention has an extremely strong ultrasonic signal, which is 51.7 times that of the pure LiNbO3 thin film sensor prepared under the same experimental conditions. Moreover, by adjusting the coating parameters, multi-waveform ultrasonic signals including longitudinal and transverse waves can be obtained.

[0028] 5. This invention effectively suppresses the attenuation of ultrasonic signals and piezoelectric constants due to radial distance by increasing the bias voltage. For a sample at a radial distance of 5 cm relative to the sputtering center, without applied bias voltage, the ultrasonic signal amplitude attenuation rate is 74%. 33 The attenuation rate is reduced to 35%; at a bias voltage of -27V, the ultrasonic signal amplitude attenuation rate is reduced to 39%, d 33 The attenuation rate decreased to 16%. Attached Figure Description

[0029] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0030] Figure 1 The surface morphology of the piezoelectric coating prepared in Example 1 is shown; Figure 2A cross-sectional morphology diagram of the piezoelectric coating prepared in Example 1 is shown; Figure 3 The XRD pattern of the piezoelectric coating prepared in Example 1 is shown; Figure 4 The ultrasonic signal test diagram of the thin-film sensor prepared in Example 1 is shown; Figure 5 The surface morphology of the piezoelectric coating prepared in Example 2 is shown. Figure 6 The XRD pattern of the piezoelectric coating prepared in Example 2 is shown; Figure 7 The ultrasonic signal test diagram of the thin-film sensor prepared in Example 2 is shown; Figure 8 The surface morphology of the piezoelectric coating prepared in Example 3 is shown; Figure 9 A cross-sectional morphology diagram of the piezoelectric coating prepared in Example 3 is shown; Figure 10 The ultrasonic signal test diagram of the thin-film sensor prepared in Example 3 is shown; Figure 11a The following are ultrasonic signal test diagrams obtained under different bias voltages and different radial distances in Examples 4-8; Figure 11b The relative amplitude diagrams of ultrasonic signals obtained under different bias voltages and different radial distances in Examples 4-8 are shown. Figure 12a The piezoelectric constants d obtained under different bias voltages and radial distances in Examples 4-8 are shown. 33 Test chart; Figure 12b The piezoelectric constants d obtained under different bias voltages and radial distances in Examples 4-8 are shown. 33 Relative amplitude diagram; Figure 13 The surface morphology of the piezoelectric coating prepared in Example 7 is shown. Figure 14 A cross-sectional morphology diagram of the piezoelectric coating prepared in Example 7 is shown; Figure 15 The cross-sectional morphology of the piezoelectric coating prepared in Comparative Example 3 is shown. Figure 16 The XRD pattern of the piezoelectric coating prepared in Comparative Example 3 is shown; Figure 17 The ultrasonic signal test diagram of the thin-film sensor prepared in Comparative Example 3 is shown; Figure 18 The XRD pattern of the piezoelectric coating prepared in Comparative Example 4 is shown. Figure 19The ultrasonic signal test diagram of the thin-film sensor prepared in Comparative Example 4 is shown; Figure 20 The ultrasonic signal test diagrams of the thin-film sensors prepared in Examples 9 and 10 are shown; Figure 21 The ultrasonic signal test diagrams of the thin-film sensors prepared in Examples 11-16 are shown; Figure 22 The transverse wave amplitude, longitudinal wave amplitude, and transverse wave to longitudinal wave amplitude ratio of the thin film sensors prepared in Examples 11-16 are shown. Figure 23 The piezoelectric constants d of the thin-film sensors prepared in Examples 11-16 are shown. 33 ; Figure 24a and Figure 24b The ultrasonic signals and piezoelectric constants d of the thin-film sensors prepared in Examples 17 and 18 are shown respectively. 33 The test results. Detailed Implementation

[0031] The endpoints and any values ​​of the ranges disclosed in this invention are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of the various ranges, the endpoint values ​​of the various ranges and individual point values, and individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed in this invention.

[0032] The technical solutions of the present invention will be clearly and completely described below with reference to specific embodiments and accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0033] Example 1 Fabrication method of ultraflat high-V-doped LiNbO3 thin film sensor (1) The front and back of the stainless steel plate were polished with 1200 grit sandpaper, and then cleaned to obtain the substrate; (2) Place the substrate into a magnetron sputtering device and use a LiNbO3 target with a V doping atomic ratio of 4%. Set the parameters as follows: RF power 900W, temperature 150℃, target-substrate distance 5.0cm, radial distance 0cm, time 8h, bias voltage 0V. (3) Vacuum the magnetron sputtering equipment, introduce Ar gas and O2 gas for deposition, the volume ratio of Ar gas and O2 gas is 6.1:1, the total flow rate of Ar gas and O2 gas is 0.9 Pa, and after the deposition is completed, an ultra-flat multi-waveform high V doped LiNbO3 piezoelectric coating is obtained. (4) Using a 99.99% high-purity Ti target, pure Ar gas was introduced at a flow rate of 0.9 Pa. The radio frequency power was controlled at 600 W, the temperature at 100 °C, the target-substrate distance at 8 cm, the radial distance at 0 cm, and the time at 4 h. After the deposition was completed, a Ti electrode layer was obtained, forming an ultra-flat high-V doped LiNbO3 thin film sensor.

[0034] The preparation method of LiNbO3 target with 4% V doping includes, S1. Preparation of nano-sized LiNbO3 powder: S11. Lithium nitrate (99.99% purity), niobium ammonium oxalate hydrate, and glycine are mixed in a molar ratio of 1:1:1.5 to obtain a mixture. The mixture is then soaked in a 0.3 mol / L nitrate aqueous solution to form a viscous precursor. S12. Pour the viscous precursor into an alumina crucible, and then calcine it at 600°C for 1 hour at a heating rate of 5°C / min under an O2 atmosphere to obtain LiNbO3 powder. S13. After natural cooling, the LiNbO3 powder is placed in ethanol and ultrasonically dispersed to avoid agglomeration. After drying at 80℃ for 5 hours, it is then passed through an ultrafiltration membrane to effectively retain particles of about 100nm, thus obtaining nano-sized LiNbO3 powder.

[0035] S2. Preparation of nanoscale highly ν-doped LiNbO3 powder: S21. Disperse nano-sized LiNbO3 powder in a composite solvent prepared by mixing glycol, water, and acetic acid in a volume ratio of 1:1:1, and then add vanadium triethoxyoxide (VO(OC2H5)3) to form a gel. S22. Collect the gel, dry it to constant weight, and then transfer it to calcine at 700℃ for 2 hours to obtain nano-sized high-V-doped LiNbO3 powder with a vanadium doping atomic ratio of 4%.

[0036] S3. Preparation of highly V-doped LiNbO3 target material: S31. Place nano-sized high-V doped LiNbO3 powder in a mold and press it into shape by isostatic pressing to form a cylindrical blank with a thickness of 4mm and a diameter of 145mm. S32. The preform was bonded to a cylindrical copper backplate with a diameter of 15.1 cm and a thickness of 3.2 mm using high-temperature resistant adhesive, resulting in a LiNbO3 target with a V doping percentage of 4% and a target density of 4.63 g / cm³. 3 .

[0037] The highly volatile doped LiNbO3 piezoelectric coating prepared in this embodiment was subjected to SEM, XRD, and ultrasonic signal measurements. The surface morphology, cross-sectional morphology, crystal structure, and ultrasonic signal of the coating are shown in the figures below. Figures 1-4 As shown, the coating prepared in this embodiment has a very smooth and flat surface and cross-sectional morphology, with excellent columnar crystal growth. The surface roughness measured by AFM is 8.2 nm, which indicates that the high-V doped LiNbO3 piezoelectric coating has an ultra-flat structure. The XRD pattern shows that the coating has a novel crystal structure with a (110) preferred orientation and does not contain impurity phases such as NbO, Nb2O5, and LiNb3O8. Under the measurement conditions of an excitation voltage of 100V and a gain of 20dB, the ultrasonic signal amplitude of the thin film sensor in this embodiment reaches 2.37V. In addition, the piezoelectric constant d of the coating is... 33 It is 16.1 pC / N.

[0038] Example 2 Fabrication method of ultraflat high-V-doped LiNbO3 thin film sensor (1) The front and back of the stainless steel plate were polished with 1200 grit sandpaper, and then cleaned to obtain the substrate; (2) Place the substrate into a magnetron sputtering device and use a LiNbO3 target with a V doping atomic ratio of 4%. Set the parameters as follows: RF power 900W, temperature 150℃, target-substrate distance 5.0cm, radial distance 0cm, time 8h, bias voltage 0V. (3) Vacuum the magnetron sputtering equipment, introduce Ar gas and O2 gas for deposition, the volume ratio of Ar gas to O2 gas is 8.3:1, the total flow rate of Ar gas and O2 gas is 0.9 Pa, and after deposition, an ultra-flat multi-waveform high V doped LiNbO3 piezoelectric coating is obtained. (4) Using a 99.99% high-purity Ti target, pure Ar gas was introduced at a flow rate of 0.9 Pa. The radio frequency power was controlled at 600 W, the temperature at 100 °C, the target-substrate distance at 8 cm, the radial distance at 0 cm, and the time at 4 h. After the deposition was completed, a Ti electrode layer was obtained, forming an ultra-flat high-V doped LiNbO3 thin film sensor.

[0039] The preparation method of the LiNbO3 target with 4% V doping atoms is the same as in Example 1.

[0040] The highly volatile doped LiNbO3 piezoelectric coating prepared in this embodiment was subjected to SEM, XRD, and ultrasonic signal measurements. The surface morphology, crystal structure, and ultrasonic signal of the coating are shown in the figures below. Figures 5-7As shown. It can be seen that the coating prepared in this embodiment has a very smooth and flat surface and cross-sectional morphology, with excellent columnar crystal growth. The surface roughness measured by AFM is 7.6 nm, which indicates that the high-V doped LiNbO3 piezoelectric coating has an ultra-flat structure. The XRD pattern shows that the coating has a novel crystal structure with a (110) preferred orientation and does not contain impurity phases such as NbO, Nb2O5, and LiNb3O8. Under the measurement conditions of an excitation voltage of 100V and a gain of 20dB, the ultrasonic signal amplitude of the thin film sensor in this embodiment reaches 6.2V. In addition, the piezoelectric constant d of the coating is... 33 It is 20.1 pC / N.

[0041] Example 3 Fabrication method of ultraflat high-V-doped LiNbO3 thin film sensor (1) The front and back of the stainless steel plate were polished with 1200 grit sandpaper, and then cleaned to obtain the substrate; (2) Place the substrate into a magnetron sputtering device and use a LiNbO3 target with a V doping atomic ratio of 4%. Set the parameters as follows: RF power 900W, temperature 150℃, target-substrate distance 5.0cm, radial distance 0cm, time 8h, bias voltage 0V. (3) Vacuum the magnetron sputtering equipment, introduce Ar gas and O2 gas for deposition, the volume ratio of Ar gas and O2 gas is 6.1:1, the total flow rate of Ar gas and O2 gas is 0.6 Pa, and after the deposition is completed, an ultra-flat multi-waveform high V doped LiNbO3 piezoelectric coating is obtained. (4) Using a 99.99% high-purity Ti target, pure Ar gas was introduced at a flow rate of 0.9 Pa. The radio frequency power was controlled at 600 W, the temperature at 100 °C, the target-substrate distance at 8 cm, the radial distance at 0 cm, and the time at 4 h. After the deposition was completed, a Ti electrode layer was obtained, forming an ultra-flat high-V doped LiNbO3 thin film sensor.

[0042] The preparation method of the LiNbO3 target with 4% V doping atoms is the same as in Example 1.

[0043] The highly volatile doped LiNbO3 piezoelectric coating prepared in this embodiment was subjected to SEM and ultrasonic signal measurements. The surface morphology, cross-sectional morphology, and ultrasonic signal of the coating are shown in the figures below. Figures 8-10 As shown, the coating prepared in this embodiment has a very smooth and flat surface and cross-sectional morphology, with excellent columnar crystal growth. The surface roughness measured by AFM is 8.3 nm, indicating that the high-V doped LiNbO3 piezoelectric coating has an ultra-flat structure. Under the measurement conditions of an excitation voltage of 100V and a gain of 20dB, the ultrasonic signal amplitude of the thin-film sensor in this embodiment reached 6.1V. Furthermore, the piezoelectric constant d of the coating... 33 It is 20.2 pC / N.

[0044] Example 4 Fabrication methods for ultraflat and ultraflat multi-waveform highly V-doped LiNbO3 thin film sensors (1) The front and back of the stainless steel plate were polished with 1200 grit sandpaper, and then cleaned to obtain the substrate; (2) Place the substrate into the magnetron sputtering equipment and use a LiNbO3 target with a V doping atomic ratio of 4%. Set the parameters including RF power of 900W, temperature of 150℃, target-substrate distance of 5.0cm, time of 8h, bias voltage of 0V, and adjust the radial distances to 0cm, 1cm, 2cm, 3cm, 4cm and 5cm respectively. (3) Vacuum the magnetron sputtering equipment, introduce Ar gas and O2 gas for deposition, the volume ratio of Ar gas and O2 gas is 8.3:1, the total flow rate of Ar gas and O2 gas is 0.6 Pa, and after the deposition is completed, an ultra-flat multi-waveform high V doped LiNbO3 piezoelectric coating is obtained. (4) Using a 99.99% high-purity Ti target, pure Ar gas is introduced at a flow rate of 0.9 Pa. The radio frequency power is controlled at 600 W, the temperature at 100 °C, the target-substrate distance at 8 cm, the radial distance at 0 cm, and the time at 4 h. After deposition, a Ti electrode layer is obtained, forming an ultra-flat multi-waveform high-V doped LiNbO3 thin film sensor.

[0045] The preparation method of the LiNbO3 target with a V doping atomic ratio of 4% is the same as in Example 1. When the radial distance is 0 cm, an ultra-flat high V doped LiNbO3 thin film sensor is obtained; when the radial distance is 1 cm, 2 cm, 3 cm, 4 cm, and 5 cm, an ultra-flat multi-waveform high V doped LiNbO3 thin film sensor is obtained.

[0046] Example 5 The difference compared to Example 4 is that the bias voltage is set to -7V.

[0047] Example 6 The difference from Example 4 is that the bias voltage is set to -14V.

[0048] Example 7 The difference compared to Example 4 is that the bias voltage is set to -20V.

[0049] Example 8 The difference compared to Example 4 is that the bias voltage is set to -27V.

[0050] The test results of ultrasonic signals and piezoelectric constants obtained under different bias voltages and radial distances in Examples 4-8 are as follows: Figure 11a and Figure 12aAs shown, under the measurement conditions of an excitation voltage of 100V and a gain of 20dB, when the radial distance is 0, the ultrasonic signal amplitude of the thin-film sensor in Example 4 reaches 12.4V, and the piezoelectric constant d 33 It is 23.1 pC / N. From Figure 11b and Figure 12a The relative amplitude and piezoelectric constant d of ultrasonic signals under the same radial distance and different bias voltages 33 The relative amplitudes show that, relative to the sample at the sputtering center, for a sample at a radial distance of 5 cm, without applied bias voltage, the ultrasonic signal amplitude attenuation rate is 74%. 33 The attenuation rate is reduced to 35%; at a bias voltage of -27V, the ultrasonic signal amplitude attenuation rate is reduced to 39%, d 33 The attenuation rate was reduced to 16%. These results demonstrate that increasing the bias voltage can effectively suppress the attenuation of the ultrasonic signal and piezoelectric constant due to radial distance.

[0051] Figure 13 and Figure 14 The surface and cross-sectional morphology of the coating prepared at a radial distance of 0 cm in Example 7 are shown respectively. It can be seen that the coating has a very smooth and flat surface and cross-sectional morphology, with excellent columnar crystal growth. The surface roughness measured by AFM is 7.5 nm.

[0052] Comparative Example 1 Compared to Example 4, the difference lies in the use of a LiNbO3 target with a V doping percentage of 3.8% for magnetron sputtering deposition. The LiNbO3 target with a V doping percentage of 3.8% is prepared using the same method as in Example 1, except for the V doping amount, which will not be repeated here.

[0053] The results show that, under the measurement conditions of an excitation voltage of 100V and a gain of 20dB, the piezoelectric coating obtained in Comparative Example 1 exhibits an ultrasonic signal amplitude of only 0.2V and a piezoelectric constant dp. 33 The value is 7.6 pC / N, which is much lower than the value of the piezoelectric coating prepared in Example 4.

[0054] Comparative Example 2 Compared to Example 4, the difference lies in the use of a LiNbO3 target with a V doping percentage of 9.5% for magnetron sputtering deposition. The LiNbO3 target with a V doping percentage of 9.5% is prepared using the same method as in Example 1, except for the V doping amount, which will not be repeated here.

[0055] The results show that, under the measurement conditions of an excitation voltage of 100V and a gain of 20dB, the ultrasonic signal amplitude of the thin-film sensor obtained in Comparative Example 2 is only 0.05V, and the piezoelectric constant d is... 33The value is 3.5 pC / N, which is much lower than the value of the piezoelectric coating prepared in Example 4.

[0056] Comparative Example 3 The difference compared to Example 4 is that the volume ratio of Ar gas to O2 gas is 4:1.

[0057] Figures 15-17 The cross-sectional morphology, XRD pattern, and ultrasonic signal test results of the piezoelectric coating prepared in Comparative Example 3 are shown. It can be seen that when the volume ratio of Ar to O2 is too low, the coating does not possess a columnar crystal morphology, and the preferred orientation is (012). Under the measurement conditions of an excitation voltage of 100V and a gain of 40dB, the ultrasonic signal amplitude is only 1.1V, meaning that under an excitation voltage of 100V and a gain of 20dB, the ultrasonic amplitude is only 0.11V, far lower than the value in Example 4.

[0058] Comparative Example 4 The difference compared to Example 4 is that the total flow rate of Ar and O2 is 1.5 Pa.

[0059] Figure 18 and Figure 19 The XRD patterns and ultrasonic signal test results of the piezoelectric coating of Comparative Example 4 are shown respectively. It can be seen that when the total flow rate of Ar and O2 is too high, the preferred orientation of the coating is (012), and the LiNb3O8 impurity phase is present. Under the measurement conditions of excitation voltage of 100V and gain of 40dB, the ultrasonic signal amplitude is only 1.25V, that is, under the measurement conditions of excitation voltage of 100V and gain of 20dB, the ultrasonic signal amplitude is only 0.125V, which is much lower than the value of Example 4.

[0060] Comparative Example 5 The difference from Example 4 is that magnetron sputtering deposition was performed using a V-undoped LiNbO3 target. The method for preparing the V-undoped LiNbO3 target includes... S1. Preparation of nanoscale LiNbO3: S11. Lithium nitrate (99.99% purity), niobium ammonium oxalate hydrate, and glycine are soaked in a 0.3 mol / L nitrate aqueous solution to form a viscous precursor. S12. Pour the viscous precursor into an alumina crucible, and then calcine it at 600°C for 1 hour at a heating rate of 5°C / min under an O2 atmosphere to obtain LiNbO3 powder. S13. After natural cooling, the LiNbO3 powder is placed in ethanol and ultrasonically dispersed to avoid agglomeration. After drying at 80℃ for 5 hours, it is then passed through an ultrafiltration membrane to effectively retain particles of about 100nm, thus obtaining nano-sized LiNbO3 powder.

[0061] S2. Preparation of V-doped LiNbO3 target material: S21. Place nano-sized LiNbO3 powder in a mold and press it into shape by isostatic pressing to form a cylindrical blank with a thickness of 4mm and a diameter of 145mm. S22. The preform is bonded to a cylindrical copper backplate with a diameter of 15.1 cm and a thickness of 3.2 mm using high-temperature resistant adhesive to obtain a V-undoped LiNbO3 target with a target density of 4.635 g / cm³. 3 .

[0062] The undoped LiNbO3 thin film sensor obtained in Comparative Example 5, under measurement conditions of 100V excitation voltage and 20dB gain, exhibits an ultrasonic signal amplitude of only 0.24V and a piezoelectric constant d. 33 It is 3.0 pC / N, which is much lower than the value in Example 4.

[0063] In summary, the ultraflat, multi-waveform, high-V-doped LiNbO3 thin-film sensor prepared by this invention exhibits excellent piezoelectric properties, with a piezoelectric constant dp. 33 The performance was significantly improved, reaching 23.1 pC / N, which is 3.8 times that of pure lithium niobate crystals and 7.7 times that of pure LiNbO3 piezoelectric coatings prepared under the same experimental conditions; it also has extremely strong ultrasonic signals, which are 51.7 times that of pure LiNbO3 thin film sensors prepared under the same experimental conditions.

[0064] Example 9 The difference compared to Example 1 is that the coating temperature of the ultra-flat, multi-waveform, high-V-doped LiNbO3 coating is 200°C.

[0065] Example 10 Compared with Example 1, the difference is that the coating temperature of the ultra-flat multi-waveform high-V doped LiNbO3 coating is 200°C and the coating time is 7 hours.

[0066] The ultraflat, multi-waveform, high-V-doped LiNbO3 thin-film sensors obtained in Examples 9-10 all acquired multi-waveform ultrasonic signals, including longitudinal waves (LW) and transverse waves (SW), under measurement conditions of an excitation voltage of 100V and a gain of 10dB. Figure 20 .

[0067] Example 11 The difference compared to Example 2 is that the radial distance of the magnetron sputtering setting is 1 cm.

[0068] Example 12 The difference compared to Example 2 is that the radial distance of the magnetron sputtering setting is 2cm.

[0069] Example 13 The difference compared to Example 2 is that the radial distance of the magnetron sputtering setting is 3cm.

[0070] Example 14 The difference compared to Example 2 is that the radial distance of the magnetron sputtering setting is 4 cm.

[0071] Example 15 The difference compared to Example 2 is that the radial distance of the magnetron sputtering setting is 5 cm.

[0072] Example 16 The difference compared to Example 2 is that the radial distance of the magnetron sputtering setting is 6 cm.

[0073] The ultraflat, multi-waveform, high-V-doped LiNbO3 thin film sensors obtained in Examples 11-16, under measurement conditions of 100V excitation voltage and 20dB gain, yielded ultrasonic signals as follows: Figure 21 As can be seen, multi-waveform ultrasound signals, including longitudinal (LW) and transverse (SW) waves, were obtained at radial distances of 1cm, 2cm, 3cm, 4cm, and 5cm. Furthermore, the amplitudes of the SW wave at 1.26μs and the LW wave at 1.09μs, as well as the amplitude ratio of the LW and SW waves, are shown below. Figure 22 This indicates that a radial distance of 3 cm is most favorable for obtaining ultrasonic signals with higher shear wave intensity. The piezoelectric constant d of the thin-film sensors prepared in Examples 11-16... 33 like Figure 23 .

[0074] Example 17 The difference compared to Example 6 is that a LiNbO3 target with a V doping atom ratio of 9% is used.

[0075] Example 18 The difference compared to Example 6 is that a LiNbO3 target with 14% V doping atoms is used.

[0076] Comparative Example 6 The difference compared to Example 6 is that a LiNbO3 target with 16% V doping atoms is used.

[0077] The test results of ultrasonic signals and piezoelectric constants obtained from LiNbO3 targets with different V doping atom percentages in Examples 17-18 are as follows: Figure 24a and Figure 24b As shown, when the percentage of V doped atoms in the LiNbO3 target is between 4% and 14%, thin-film sensors with excellent piezoelectric properties can be obtained. However, for Comparative Example 6, where the percentage of V doped atoms is 16%, the prepared thin film no longer possesses piezoelectricity, and the ultrasonic signal is 0V.

[0078] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments or make equivalent substitutions for some of the technical features. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for fabricating an ultraflat, multi-waveform, high-V-doped LiNbO3 thin film sensor, characterized in that, include, Using LiNbO3 targets and electrode targets with a V doping atomic ratio of 4%-14%, an ultra-flat, multi-waveform, highly V-doped LiNbO3 piezoelectric coating and an electrode layer were sequentially prepared on the substrate surface by magnetron sputtering. The method for preparing the LiNbO3 target includes, Lithium nitrate, niobium ammonium oxalate hydrate, and amino acids were soaked in a nitrate solution to form a viscous precursor. The viscous precursor was then heat-treated to obtain nano-sized LiNbO3 powder. Nanoscale LiNbO3 powder was dispersed in a composite solvent and then introduced into a V source to form a gel. The gel was then heat-treated to obtain nanoscale highly V-doped LiNbO3. Nanoscale high-V-doped LiNbO3 was pressed to obtain LiNbO3 targets with a V-doping atomic ratio of 4%-14%.

2. The method for fabricating the ultraflat multi-waveform high-V-doped LiNbO3 thin film sensor according to claim 1, characterized in that, The molar ratio of lithium nitrate, niobium ammonium oxalate, and amino acids is 1:1:0.5-2; The concentration of the nitrate solution is 0.2-0.5 mol / L.

3. The method for fabricating the ultraflat multi-waveform high-V-doped LiNbO3 thin film sensor according to claim 1, characterized in that, The composite solvent is prepared by mixing ethylene glycol, water, and acetic acid in a volume ratio of 0.5-1.5:1:0.5-1.

5.

4. The method for fabricating the ultraflat multi-waveform high-V-doped LiNbO3 thin film sensor according to claim 1, characterized in that, The heat treatment is carried out at 500-900℃ for 0.5-2 hours.

5. The method for fabricating the ultraflat multi-waveform high-V-doped LiNbO3 thin film sensor according to claim 1, characterized in that, The size of the nano-sized LiNbO3 and the nano-sized high-V doped LiNbO3 powder is 80-150 nm.

6. The method for fabricating the ultraflat multi-waveform high-V-doped LiNbO3 thin film sensor according to claim 1, characterized in that, The specific magnetron sputtering parameters for preparing ultraflat, multi-waveform, high-V-doped LiNbO3 piezoelectric coatings include... The experiment was conducted under Ar and O2 atmospheres, with a total flow rate of 0.6-0.9 Pa. The radio frequency power was controlled at 800-900 W, the temperature at 150-250 °C, the target distance at 4-5.5 cm, the radial distance at 0-6 cm, and the time at 2-8 h.

7. The method for fabricating an ultraflat, multi-waveform, high-V-doped LiNbO3 thin film sensor according to claim 6, characterized in that, During magnetron sputtering, the introduced volumes of Ar and O2 gases are also controlled, with a volume ratio of Ar to O2 of 6.1-8.3:

1.

8. The method for fabricating an ultraflat, multi-waveform, high-V-doped LiNbO3 thin film sensor according to claim 6, characterized in that, During magnetron sputtering, a bias voltage of -34V to -7V is also set between the target and the substrate.

9. The method for fabricating an ultraflat, multi-waveform, high-V-doped LiNbO3 thin film sensor according to claim 1, characterized in that, The specific magnetron sputtering parameters for preparing the electrode layer include: Using 99.99% high-purity Ti target material, pure Ar gas is introduced at a flow rate of 0.6-1.2 Pa, and the RF power is controlled at 500-800W, the temperature at 50-150℃, the target-substrate distance at 7-10cm, the radial distance at 0-6cm, and the time at 2-5h.

10. A superflat, multi-waveform, high-V-doped LiNbO3 thin-film sensor, characterized in that, It is obtained by the preparation method according to any one of claims 1-8.

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