N-doped ZnO target material and method for preparing the same

Abstract

This invention relates to an N-doped ZnO target and its preparation method, belonging to the field of semiconductor target technology. To address the shortcomings of existing N-doped ZnO materials, such as low N solid solubility, uneven doping, unstable p-type conductivity, poor target density, and difficulty in mass production, this invention uses zinc glycerate as a slow-release nitrogen source, combined with Al2O3 and Li2CO3 composite additives, and integrates wet ball milling, cold isostatic pressing, and vacuum gradient sintering processes to prepare highly uniform and dense p-type ZnO targets. This invention effectively suppresses high-temperature escape of N and lattice defects, achieving an N lattice solid solubility of 0.3–1.2 at.%, a micro-area N content fluctuation of ≤4%, a target density of ≥98.5%, and stable and excellent p-type conductivity. The process of this invention is simple and controllable, low-cost, requires no precious metal doping, is compatible with magnetron sputtering, and can be widely applied to ZnO-based optoelectronic devices such as ultraviolet emission and photodetectors.

Description

Technical Field

[0001] This invention belongs to the field of semiconductor target preparation technology, specifically relating to an N-doped ZnO target and its preparation method, which is particularly suitable for thin film preparation processes such as pulsed laser deposition (PLD) and magnetron sputtering, and can be widely used in the preparation of optoelectronic devices such as ultraviolet light-emitting diodes (UV-LEDs), photodetectors, and transparent conductive films. Background Technology

[0002] ZnO, as a wide bandgap semiconductor material, boasts a high bandgap of 3.37 eV at room temperature and an exciton binding energy of 60 meV. Compared to materials such as GaN and SiC, it exhibits significant advantages in optoelectronic devices, making it one of the ideal materials for fabricating ultraviolet light-emitting and photodetector devices. ZnO is intrinsically a strong n-type semiconductor, primarily due to intrinsic donor defects such as oxygen vacancies (V_O) and zinc interstitial atoms (Zn_i) present in the crystal. The fabrication of p-type ZnO is a key bottleneck in realizing ZnO-based homojunction devices (such as LEDs and LDs).

[0003] Among numerous p-type doping elements, nitrogen (N) is considered the most promising p-type dopant due to its ionic radius being close to that of oxygen atoms and its ability, as a group V element, to replace oxygen atoms in the ZnO lattice to form shallow acceptor energy levels. However, existing N-doped ZnO target fabrication techniques still face several unresolved issues: First, N has extremely low solid solubility in ZnO, resulting in poor doping efficiency and difficulty in achieving effective p-type transition; second, self-compensation effects are easily generated during doping, with donor defects offsetting the acceptor effect of N, leading to unstable electrical properties of the target and subsequently fabricated thin films; third, existing fabrication methods often suffer from complex processes, expensive equipment, low target density, and uneven grain size, failing to meet the demands of large-scale industrial production, and the resulting targets exhibit poor thin film crystal quality and photoelectric properties when used for thin film deposition.

[0004] Current N-doped ZnO technologies primarily focus on thin film preparation or powder doping, with limited attention paid to target material optimization. For instance, some techniques use Zn3N2 as the N source, but Zn3N2 suffers from poor stability and decomposes easily at high temperatures, making precise control of the N doping amount difficult. Other techniques employ co-doping to improve N solid solubility, but often utilize noble metals such as Ga and In, increasing preparation costs and failing to address the core issues of target density and doping uniformity. Therefore, developing a uniformly doped, highly dense, electrically stable, simple, and cost-effective N-doped ZnO target and its preparation method is of significant practical value and market potential, and represents a pressing technical challenge in this field. Summary of the Invention

[0005] To address the shortcomings of existing N-doped ZnO targets, such as uneven doping, poor density, unstable electrical properties, complex preparation processes, high costs, and difficulty in industrial production, this invention provides an N-doped ZnO target and its preparation method. By optimizing the target composition design and preparation process parameters, efficient and uniform N doping is achieved, improving the target density and crystal quality, reducing the self-compensation effect, simplifying the process, reducing costs, and meeting the needs of large-scale production of optoelectronic devices.

[0006] The technical solution to the above technical problem is: an N-doped ZnO target material, with ZnO as the matrix, the doping components including an N source and an auxiliary dopant, the raw material composition of the target material by molar percentage includes: ZnO: 88.0-97.5 mol%, N source: 1.5-8.0 mol%, auxiliary dopant: 0.5-4.0 mol%.

[0007] The nitrogen source is zinc glycine, whose decomposition temperature matches the sintering temperature of ZnO. This allows for the slow release of nitrogen during sintering, preventing nitrogen escape at high temperatures. Furthermore, the amino and carboxyl groups in its molecular structure can react with ZnO. 2+ This forms stable coordination, promoting the uniform dispersion of N elements in the ZnO lattice.

[0008] The auxiliary dopant is a composite system of Al2O3 and Li2CO3, with a molar ratio of 1:0.8 to 1.2. Al2O3 can effectively increase the solid solubility of N in ZnO, suppress the formation of oxygen vacancy defects, and reduce the self-compensation effect. Li2CO3 can lower the sintering temperature of the target material and promote grain densification. Meanwhile, Li... + It can help adjust lattice distortion and further improve the uniformity of N doping.

[0009] Furthermore, the target material has a density ≥98.5%, a grain size of 1–5 μm with uniform distribution, a relative fluctuation of N element content in different micro-regions of the target material ≤4%, excellent N element lattice solid solution uniformity, and a resistivity of 1.2 × 10⁻⁶ at room temperature. -3 ~8.5×10 -3 Ω·cm, hole concentration is 1.0×10 18 ~5.0×10 19 cm -3 The migration rate is 15–35 cm. 2 / (V·s), can be directly used in thin film deposition processes such as magnetron sputtering, and the prepared p-type ZnO thin films have excellent crystal quality and stable performance; among them, the actual solid solubility of N element in ZnO lattice is 0.3~1.2 at.% (atomic percentage).

[0010] Furthermore, the ZnO is ZnO powder with a purity ≥ 99.99%, the zinc glycine has a purity ≥ 99.95%, and the Al2O3 and Li2CO3 are Al2O3 powder and Li2CO3 powder with a purity ≥ 99.9% respectively.

[0011] Another technical solution of the present invention is: the preparation method of the above-mentioned N-doped ZnO target material includes the following steps: (1) Raw material pretreatment: ZnO, zinc glycine, Al2O3 and Li2CO3 raw materials are placed in a vacuum drying oven to dry and remove moisture and impurities from the raw materials. After drying, each raw material is sieved through a screen to ensure uniform particle size and avoid large particles of impurities affecting the quality of the target material.

[0012] (2) Ingredients and mixing: Weigh ZnO powder, zinc glycine, Al2O3 powder and Li2CO3 powder accurately by molar percentage, put them into the mixing tank, add pure water and dispersant, and prepare a slurry with a certain solid content. The slurry is wet ball milled in a ball mill to obtain a uniform mixed slurry.

[0013] (3) Slurry drying and granulation: The mixed slurry is placed in a vacuum freeze dryer for freeze drying to remove anhydrous ethanol from the slurry and obtain a dry mixed powder; the dried mixed powder is placed in a granulator, a binder is added for granulation, and uniform particles are obtained, which are convenient for subsequent pressing and molding.

[0014] (4) Press molding: The granules are formed in a mold and then pressed into a blank by cold isostatic pressing.

[0015] (5) Degreasing treatment: Place the billet in the furnace and degrease it by gradient heating in an air atmosphere. After degreasing, cool it naturally to room temperature to remove the binder and residual organic matter in the billet and avoid the generation of pores during sintering.

[0016] (6) Sintering treatment: The degreased blank is placed in a vacuum sintering furnace and sintered under vacuum conditions with gradient heating, and finally cooled to room temperature. During the sintering process, zinc glycine slowly decomposes to release N2 and NH3. The N element diffuses into the ZnO lattice at high temperature to achieve uniform doping. At the same time, Al2O3 and Li2CO3 work together to promote grain growth and densification, and finally N-doped ZnO target material is obtained.

[0017] Furthermore, in step (1), the drying temperature is 80-100℃, the drying time is 2-4h, and a 200-300 mesh sieve is used for sieving.

[0018] Furthermore, in step (2), the dispersant is anhydrous ethanol, and the amount added is 20-30% of the total mass of the raw materials. Pure water is added to prepare a slurry with a solid content of 30-60%. The slurry is wet-milled in a ball mill for 6-10 hours to obtain a uniform mixed slurry.

[0019] Furthermore, in step (3), the freeze-drying temperature is -40 to -30°C, the vacuum degree is ≤10Pa, and the drying time is 8 to 12 hours; the binder is polyvinyl alcohol, and the amount added is 2 to 5% of the mass of the mixed powder, and the particle size after granulation is 50 to 100 μm.

[0020] Furthermore, in step (4), the cold isostatic pressure is 150-200 MPa, and the holding time is 10-15 min.

[0021] Furthermore, in step (5), the gradient heating program for defatting is as follows: heating from room temperature to 180-220℃ at a heating rate of 0.4-0.6℃ / min, and holding for 0.8-1.2h; after holding, heating to 380-420℃ at a heating rate of 0.2-0.4℃ / min, and holding for 1.5-2.5h; after holding, heating to 550-650℃ at a heating rate of 0.1-0.3℃ / min, and holding for 0.8-1.2h; and then naturally cooling to room temperature after holding.

[0022] Furthermore, in step (6), the vacuum degree is ≤5×10 -3 Pa, the gradient heating program for sintering is as follows: heating from room temperature to 750-850℃ at a heating rate of 4-6℃ / min, holding for 1.5-2.5h; after holding, heating to 1100-1250℃ at a heating rate of 2-4℃ / min, holding for 4-8h; cooling to room temperature at a cooling rate of 3-5℃ / min.

[0023] Compared with the prior art, the present invention has the following significant advantages: 1. Zinc glycine was selected as the N source, whose decomposition temperature is precisely matched with the sintering temperature of ZnO. It can slowly release N element during sintering, effectively avoiding the escape of N element at high temperature. This solves the technical problems of poor stability and difficulty in controlling the amount of N doping of traditional N sources (such as Zn3N2 and NH4NO3). The actual solid solubility of N element in ZnO lattice is controlled at 0.3 to 1.2 at.%, which provides a guarantee for the stable preparation of p-type ZnO. At the same time, Al2O3 and Li2CO3 were used as auxiliary dopants. The two worked synergistically to improve the solid solubility of N element, reduce the sintering temperature, and promote the densification of the target material.

[0024] 2. By optimizing the composition design and precisely controlling the ratio of N source to auxiliary dopant, donor defects such as oxygen vacancies and zinc interstices in ZnO are effectively suppressed, reducing the self-compensation effect and achieving uniform and efficient N doping. The relative fluctuation of N content in different micro-regions of the target material is controlled within 4%, solving the core pain points of uneven doping and unstable electrical properties of existing N-doped ZnO targets. At the same time, the optimized preparation process combines cold isostatic pressing and vacuum gradient sintering, simplifying the process steps, reducing equipment costs, and solving the problems of complex processes and difficulty in industrial production of traditional preparation methods.

[0025] 3. Excellent performance: The prepared N-doped ZnO target has a density of ≥98.5%, uniform grain size, and relative fluctuation of N element content in different micro-regions of the target ≤4%. The N element lattice solid solution uniformity is excellent, and the actual solid solubility of N element is 0.3~1.2 at.%. The electrical properties are stable, and the resistivity, hole concentration and mobility at room temperature are all better than those of existing similar targets. When used to prepare p-type ZnO thin films by magnetron sputtering, the film has high crystal quality and excellent photoelectric properties, which can directly meet the preparation requirements of optoelectronic devices such as UV-LEDs and photodetectors.

[0026] 4. Controllable cost and easy to industrialize: The raw materials selected in this invention are all conventional chemical raw materials, which are inexpensive and easy to obtain. No expensive equipment or complex process steps are required. The preparation process has low energy consumption and low pollution, and can achieve large-scale production, with significant economic benefits and application prospects. Detailed Implementation

[0027] To better illustrate the objectives, technical solutions, and advantages of this invention, the invention will be further described below with reference to specific embodiments. Those skilled in the art should understand that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention. Example 1

[0028] A type of N-doped ZnO target material, the components of which are as follows (in molar percentage): ZnO: 95.0 mol%, zinc glycine: 3.5 mol%, Al2O3: 0.8 mol%, Li2CO3: 0.7 mol% (the molar ratio of Al2O3 to Li2CO3 is 1:0.875).

[0029] Its preparation method includes the following steps: 1. Raw material pretreatment: Select ZnO powder with a purity of 99.99%, zinc glycine with a purity of 99.95%, Al2O3 powder with a purity of 99.9%, and Li2CO3 powder. Place them in a vacuum drying oven and dry them at 90℃ for 3 hours. After drying, sieve them through a 250-mesh sieve.

[0030] 2. Ingredients and Mixing: Accurately weigh the above components by molar percentage and place them in a mixing tank. Add anhydrous ethanol (25% of the total mass of raw materials) and pure water to prepare a slurry with a solid content of 30%. Wet ball mill the slurry in a ball mill for 8 hours to obtain a mixed slurry.

[0031] 3. Slurry drying and granulation: The mixed slurry is placed in a vacuum freeze dryer and freeze-dried at -35℃ and 8Pa vacuum for 10 hours to obtain a dried mixed powder; 3% PVA binder is added and granulated to obtain particles with a particle size of 70-80μm.

[0032] 4. Pressing and molding: The granules are placed in a mold and then cold isostatically pressed at a pressure of 180 MPa for 12 minutes to obtain the blank.

[0033] 5. Degreasing treatment: Place the billet in a degreasing furnace and degrease it under a gradient temperature in an air atmosphere: room temperature → 200℃ (0.5℃ / min, hold for 1h) → 400℃ (0.3℃ / min, hold for 2h) → 600℃ (0.2℃ / min, hold for 1h), and then cool it naturally to room temperature.

[0034] 6. Sintering treatment: Place the degreased green body into a vacuum sintering furnace and evacuate it to a vacuum level of 3×10⁻⁶. -3 Pa, gradient heating sintering: room temperature → 800℃ (5℃ / min, hold for 2h) → 1180℃ (3℃ / min, hold for 6h), cooling rate 4℃ / min, cool to room temperature to obtain N-doped ZnO target material.

[0035] The performance of the target material prepared in this embodiment was tested, and the results are as follows: density 98.8%, grain size 2-4 μm, relative fluctuation of N element content in different micro-regions of the target material ≤3.2%, excellent uniformity of N element lattice solid solution, actual solid solubility of N element 0.65 at.%, and room temperature resistivity 3.2 × 10⁻⁶. -3 Ω·cm, hole concentration 2.8×10 18 cm -3 Mobility 28cm 2 / (V·s). Example 2

[0036] A type of N-doped ZnO target material, the components of which are as follows (in molar percentage): ZnO: 92.0 mol%, zinc glycine: 6.0 mol%, Al2O3: 1.0 mol%, Li2CO3: 1.0 mol% (the molar ratio of Al2O3 to Li2CO3 is 1:1).

[0037] The preparation method is basically the same as that in Example 1, except that the following parameters are changed: ball milling time 10h, sintering temperature 1220℃, and sintering holding time 7h.

[0038] The performance of the target material prepared in this embodiment was tested, and the results are as follows: density 99.1%, grain size 3-5 μm, relative fluctuation of N element content in different micro-regions of the target material ≤3.6%, excellent uniformity of N element lattice solid solution, actual solid solubility of N element 1.12 at.%, and room temperature resistivity 2.5 × 10⁻⁶. -3 Ω·cm, hole concentration 4.2×10 18 cm -3 Mobility 32cm 2 / (V·s). Example 3

[0039] A type of N-doped ZnO target material, the components of which are as follows (in molar percentage): ZnO: 97.0 mol%, zinc glycine: 1.8 mol%, Al2O3: 0.6 mol%, Li2CO3: 0.6 mol% (the molar ratio of Al2O3 to Li2CO3 is 1:1).

[0040] The preparation method is basically the same as that in Example 1, except for the following parameters: ball milling time 6h, sintering temperature 1120℃, and sintering holding time 4h.

[0041] The performance of the target material prepared in this embodiment was tested, and the results are as follows: density 98.6%, grain size 1-3 μm, relative fluctuation of N element content in different micro-regions of the target material ≤3.8%, excellent uniformity of N element lattice solid solution, actual solid solubility of N element 0.32 at.%, and room temperature resistivity 7.8 × 10⁻⁶. -3 Ω·cm, hole concentration 1.2×10 18 cm -3 Mobility 18cm 2 / (V·s). Example 4

[0042] A type of N-doped ZnO target material, the components of which are as follows (in molar percentage): ZnO: 88.5 mol%, zinc glycine: 7.5 mol%, Al2O3: 2.0 mol%, Li2CO3: 2.0 mol% (the molar ratio of Al2O3 to Li2CO3 is 1:1).

[0043] The preparation method is basically the same as that in Example 1, except that the following parameters are changed: ball milling time 9h, sintering temperature 1250℃, and sintering holding time 8h.

[0044] The performance of the target material prepared in this embodiment was tested, and the results are as follows: density 99.2%, grain size 3-5 μm, relative fluctuation of N element content in different micro-regions of the target material ≤2.8%, excellent uniformity of N element lattice solid solution, actual solid solubility of N element 1.18 at.%, and room temperature resistivity 1.5 × 10⁻⁶. -3Ω·cm, hole concentration 4.8×10 18 cm -3 Mobility 34cm 2 / (V·s). Comparative Example 1 (without auxiliary dopant)

[0045] Composition: ZnO: 96.5 mol%, zinc glycine: 3.5 mol% (no Al2O3 and Li2CO3).

[0046] Preparation method: basically the same as in Example 1, except that the auxiliary dopants Al2O3 and Li2CO3 were removed, and the sintering temperature was adjusted to 1300℃ (because there is no Li2CO3, the sintering temperature needs to be increased to achieve densification).

[0047] Performance test results: Density 95.2%, grain size non-uniform (1-8 μm), relative fluctuation of N element content in different micro-regions of the target material ≥12.1%, poor uniformity of N element lattice solid solution, actual N element solid solubility is only 0.08 at.%, room temperature resistivity 1.8×10 -2 Ω·cm, hole concentration 8.5×10 16 cm -3 Mobility 12cm 2 / (V·s).

[0048] Analysis: Without the addition of auxiliary dopants, the solid solubility of N in ZnO is significantly reduced, and the sintering temperature is increased, resulting in severe N escape. The density of the target material and the uniformity of N distribution are greatly reduced, and the electrical performance is significantly worse than that of Example 1. This indicates that the combined use of auxiliary dopants is crucial for improving the performance of the target material. Comparative Example 2 (using a traditional N source)

[0049] Components: ZnO: 95.0 mol%, Zn3N2: 3.5 mol%, Al2O3: 0.8 mol%, Li2CO3: 0.7 mol% (consistent with the component ratios in Example 1, except that zinc glycine is replaced with Zn3N2).

[0050] Preparation method: basically the same as in Example 1, except that the N source is replaced with Zn3N2, and the temperature is strictly controlled during ball milling and sintering (to avoid premature decomposition of Zn3N2).

[0051] Performance test results: Density 96.1%, grain size 2–6 μm, relative fluctuation of N element content in different micro-regions of the target material ≥10.0%, poor uniformity of N element lattice solid solution, actual N element solid solubility 0.21 at.%, room temperature resistivity 9.2 × 10⁻⁶ -3 Ω·cm, hole concentration 1.5×10 18 cm -3Mobility 20cm 2 / (V·s).

[0052] Analysis: The traditional N source Zn3N2 has poor stability and is prone to premature decomposition during ball milling and sintering, making it difficult to control the N doping amount. The uniformity of N element distribution and electrical properties are inferior to those in Example 1, indicating that the zinc glycine selected in this invention as the N source has significant advantages. Comparative Example 3 (Single Auxiliary Dopant)

[0053] Composition: ZnO: 95.0 mol%, zinc glycine: 3.5 mol%, Al2O3: 1.5 mol% (no Li2CO3, only Al2O3 added).

[0054] Preparation method: basically the same as in Example 1, except that Li2CO3 was removed and the sintering temperature was adjusted to 1280℃.

[0055] Performance test results: Density 97.0%, grain size 2–7 μm, relative fluctuation of N element content in different micro-regions of the target material ≥7.3%, N element lattice solid solution homogeneity is average, actual N element solid solubility is 0.27 at.%, room temperature resistivity 5.8 × 10⁻⁶ -3 Ω·cm, hole concentration 2.1×10 18 cm -3 Mobility 22cm 2 / (V·s).

[0056] Analysis: Although adding only Al2O3 as a single auxiliary dopant can improve the solid solubility of N to a certain extent, it cannot effectively reduce the sintering temperature. The density of the target material and the uniformity of N element distribution are still poor, and the electrical performance is not as good as in Example 1. This indicates that the synergistic effect of Al2O3 and Li2CO3 is worse than that of single doping. Comparative Example 4 (Traditional Sintering Process)

[0057] Composition: exactly the same as in Example 1 (ZnO: 95.0 mol%, zinc glycine: 3.5 mol%, Al2O3: 0.8 mol%, Li2CO3: 0.7 mol%).

[0058] Preparation method: basically the same as in Example 1, except that vacuum sintering was replaced with air atmosphere sintering, and uniform heating was used (heating rate 5℃ / min, directly raised to 1180℃, and held for 6h).

[0059] Performance test results: Density 96.8%, grain size 3–8 μm, relative fluctuation of N element content in different micro-regions of the target material ≥8.7%, N element lattice solid solution homogeneity is average, actual N element solid solubility is 0.24 at.%, room temperature resistivity 6.5 × 10⁻⁶ -3Ω·cm, hole concentration 1.9×10 18 cm -3 Mobility 23cm 2 / (V·s).

[0060] Analysis: When using conventional air atmosphere uniform sintering, oxygen in the air reacts with nitrogen, leading to nitrogen loss. At the same time, uniform heating easily causes uneven grain growth, resulting in decreased target density and uniform nitrogen distribution. The electrical performance is inferior to that of Example 1, indicating that the vacuum gradient sintering process of the present invention has significant advantages. Performance Comparison Summary

[0061] The performance test results of Example 1 and each comparative example are summarized in the table below:

[0062] As can be seen from the above performance comparison, the N-doped ZnO target prepared in Example 1 of the present invention is significantly superior to each of the comparative examples in terms of key performance indicators such as density, uniformity of N element distribution (relative fluctuation of content), solid solubility of N element, room temperature resistivity, hole concentration and mobility, effectively solving the technical pain points of the prior art.

Claims

1. An N-doped ZnO target, characterized in that: Using ZnO as the matrix, the doping components include an N source and an auxiliary dopant. The raw material composition of the target material, by molar percentage, includes: ZnO: 88.0–97.5 mol%, N source: 1.5–8.0 mol%, and auxiliary dopant: 0.5–4.0 mol%. The N source is zinc glycine, and the auxiliary dopant is a complex system of Al₂O₃ and Li₂CO₃ in a molar ratio of 1:0.8–1.

2.

2. The N-doped ZnO target according to claim 1, characterized in that: The target material has a density ≥98.5%, a relative fluctuation of N element content in different micro-regions of the target material ≤4%, an actual solid solubility of N element in the ZnO lattice of 0.3~1.2 at.%, and a resistivity of 1.2×10 at room temperature. -3 ~8.5×10 -3 Ω·cm, hole concentration is 1.0×10 18 ~5.0×10 19 cm -3 The migration rate is 15–35 cm. 2 / (V·s).

3. An N-doped ZnO target according to claim 1 or 2, characterized in that: The ZnO is ZnO powder with a purity ≥ 99.99%, the zinc glycine has a purity ≥ 99.95%, and the Al2O3 and Li2CO3 are Al2O3 powder and Li2CO3 powder with a purity ≥ 99.9% respectively.

4. A method for preparing an N-doped ZnO target as described in any one of claims 1-3, characterized in that: Includes the following steps: (1) Raw material pretreatment: ZnO, zinc glycine, Al2O3 and Li2CO3 raw materials were dried and sieved respectively; (2) Ingredients and mixing: Weigh each raw material according to the molar percentage, add pure water and dispersant, and wet ball mill to obtain a mixed slurry; (3) Slurry drying and granulation: The mixed slurry is freeze-dried, and a binder is added for granulation to obtain uniform particles; (4) Pressing and molding: The granules are formed in a mold and then cold isostatically pressed to obtain a blank; (5) Degreasing treatment: The green body is degreased by gradual heating in air atmosphere and then cooled to room temperature; (6) Sintering treatment: The degreased green body is sintered under vacuum conditions with gradient heating and then cooled to room temperature.

5. The method for preparing an N-doped ZnO target as described in claim 4, characterized in that: In step (1), the drying temperature is 80-100℃, the drying time is 2-4h, and a 200-300 mesh screen is used for sieving.

6. The method for preparing an N-doped ZnO target as described in claim 4, characterized in that: In step (2), the dispersant is anhydrous ethanol, and the amount added is 20-30% of the total mass of the raw materials. Pure water is added to prepare a slurry with a solid content of 30-60%. The ball milling time is 6-10 hours.

7. The method for preparing an N-doped ZnO target as described in claim 4, characterized in that: In step (3), the freeze-drying temperature is -40 to -30℃, the vacuum degree is ≤10Pa, and the drying time is 8 to 12h; the binder is polyvinyl alcohol, and the amount added is 2 to 5% of the mass of the mixed powder, and the particle size after granulation is 50 to 100μm.

8. The method for preparing an N-doped ZnO target as described in claim 4, characterized in that: In step (4), the cold isostatic pressure is 150-200 MPa and the holding time is 10-15 min.

9. The method for preparing an N-doped ZnO target as described in claim 4, characterized in that: In step (5), the gradient heating program for defatting is as follows: heating from room temperature to 180-220℃ at a heating rate of 0.4-0.6℃ / min and holding for 0.8-1.2h; after holding, heating to 380-420℃ at a heating rate of 0.2-0.4℃ / min and holding for 1.5-2.5h; after holding, heating to 550-650℃ at a heating rate of 0.1-0.3℃ / min and holding for 0.8-1.2h; and then naturally cooling to room temperature after holding.

10. The method for preparing an N-doped ZnO target as described in claim 4, characterized in that: In step (6), the vacuum degree is ≤5×10 -3 Pa, the gradient heating program for sintering is as follows: heating from room temperature to 750-850℃ at a heating rate of 4-6℃ / min, holding for 1.5-2.5h; after holding, heating to 1100-1250℃ at a heating rate of 2-4℃ / min, holding for 4-8h; cooling to room temperature at a cooling rate of 3-5℃ / min.

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