A method of regulating the growth of thin film crystal structures

Abstract

The application provides a method for regulating a thin film crystal structure, and belongs to the technical field of semiconductor microelectronic and optoelectronic materials. The method comprises the following steps: (1) performing oxygen plasma treatment on the surface of a clean magnesium oxide single crystal substrate by using a molecular beam epitaxy technology, and growing a zinc oxide buffer layer; and (2) subsequently growing a MgZnO thin film on the surface of the magnesium oxide single crystal substrate by using the molecular beam epitaxy technology. The process step for growing the MgZnO thin film is that: oxygen activated by plasma, a Zn metal source and a Mg metal source are simultaneously introduced to grow the MgZnO thin film; and the crystal phase of the MgZnO thin film is a cubic structure or a hexagonal structure by regulating the temperature of the Mg metal source. The method can regulate the crystal structure by only regulating the element content in the material without changing the substrate structure. The method can not only regulate the element content in the material, but also obtain materials with different crystal phases by regulating the growth conditions.

Description

Technical Field

[0001] This invention belongs to the technical field of semiconductor microelectronics and optoelectronic materials, and particularly relates to a method for controlling the growth of thin film crystal structures. Background Technology

[0002] Zinc oxide (ZnO) is an extremely important group II-VI wide bandgap semiconductor material and a candidate material for fabricating ultraviolet optoelectronic devices (such as LEDs and lasers). At room temperature, its thermodynamically stable phase is a hexagonal wurtzite structure. However, under specific conditions, ZnO can also exist in a cubic zincblende structure. Changes in structural symmetry directly affect its optical polarization properties and carrier transport behavior. Cubic ZnO may exhibit different luminescent properties than its hexagonal phase. The wider bandgap of cubic ZnMgO compared to ZnO makes it valuable for the fabrication of transparent electrodes and high-power, high-frequency electronic devices, and also provides more possibilities for designing novel optoelectronic devices.

[0003] Methods to induce phase transitions in ZnO crystal structures include changing the substrate, optimizing growth conditions, and doping. For example, a tetragonal MgO (100) substrate is more conducive to the growth of cubic ZnO than a hexagonal MgO (111) substrate. By adjusting growth conditions (temperature, pressure, precursor flow rate), ZnO can be grown in a metastable cubic phase. Introducing specific doping elements can change the free energy of the system, thereby stabilizing the metastable phase. For example, when the Mg content in ZnMgO reaches a certain proportion, the alloy will transform from a hexagonal phase to a cubic phase. In the invention patent CN103205706A, "A method for preparing a cubic MgZnO thin film," the MgZnO thin film prepared by pulsed laser deposition exhibits a cubic structure, demonstrating that the incorporation of Mg can effectively stabilize the cubic phase of ZnO. However, this method of fixing the element content ratio in the target material makes it difficult to effectively control the element ratio in the alloy, and even more difficult to effectively regulate the transformation of the crystal structure between hexagonal and cubic. In summary, a method for controlling the crystal structure of materials by adjusting the element content is urgently needed to achieve controllable growth of materials. Summary of the Invention

[0004] To address the aforementioned technical problems, this invention proposes a method for controlling the crystal structure of grown thin films. This method can control the crystal structure by adjusting the element content in the material without altering the substrate structure. Furthermore, it can not only control the element content in the material but also obtain materials with different crystalline phases by adjusting the growth conditions. Moreover, this technique has excellent reproducibility in experiments.

[0005] To achieve the above objectives, the technical solution of the present invention is implemented as follows:

[0006] A method for controlling the structure of thin film crystals includes the following steps:

[0007] (1) The surface of the cleaned magnesium oxide single crystal substrate is treated with oxygen plasma by molecular beam epitaxy and a zinc oxide buffer layer is grown.

[0008] (2) Subsequently, molecular beam epitaxy was used to grow MgZnO thin films on the surface of magnesium oxide single crystal substrates;

[0009] The process steps for growing MgZnO thin films are as follows: simultaneously introducing plasma-activated oxygen, a Zn metal source, and a Mg metal source to grow MgZnO thin films; and adjusting the temperature of the Mg metal source to make the crystal phase of the MgZnO thin film cubic or hexagonal.

[0010] The molecular beam epitaxy techniques in steps (1) and (2) are performed continuously within the same vacuum chamber.

[0011] The oxygen plasma treatment conditions are as follows: the temperature of the magnesium oxide single crystal substrate is 480-500℃, and the oxygen pressure is 4×10⁻⁶. -5 -6×10 -5 Torr, time is 0.5-2 hours.

[0012] Preferably, the temperature of the magnesium oxide single crystal substrate is 490°C and the oxygen pressure is 5 × 10⁻⁶. -5 Torr, duration 1 hour.

[0013] The growth conditions for the zinc oxide buffer layer are as follows: the temperature of the magnesium oxide single crystal substrate is 390-410℃, the zinc source temperature is 320-340℃, and the oxygen pressure is 0.5×10⁻⁶. -5 -2×10 -5 Torr, growth time is 5-30 minutes.

[0014] Preferably, the temperature of the magnesium oxide single crystal substrate is 400°C, the zinc source temperature is 330°C, and the oxygen pressure is 1×10⁻⁶. -5 Torr, growth time is 10 min.

[0015] The growth conditions for the MgZnO thin film in step (2) are as follows: the temperature of the magnesium oxide single crystal substrate is 365-375℃, the zinc source temperature is 325-335℃, the Mg source temperature is 350-380℃, and the oxygen pressure is 1×10⁻⁶. -5 -3×10 -5 Torr, growth time is 0.5-2 hours.

[0016] Preferably, the temperature of the magnesium oxide single crystal substrate is 370°C, the zinc source temperature is 330°C, the Mg source temperature is 350-380°C, and the oxygen pressure is 2×10⁻⁶. -5 Torr, growth time is 1.5h.

[0017] When the temperature of the Mg metal source is 350-370℃, the MgZnO thin film has a hexagonal crystal structure.

[0018] When the temperature of the Mg metal source is 375-380℃, the MgZnO thin film has a cubic crystal structure.

[0019] Preferably, when the temperature of the Mg metal source is 380°C, the MgZnO thin film has a cubic crystal structure.

[0020] In step (2), nitrogen gas activated by plasma is introduced simultaneously with oxygen, a Zn metal source, and a Mg metal source to perform nitrogen doping treatment and obtain a MgZnO thin film; the pressure of the nitrogen gas is 3 × 10⁻⁶. -5 -5×10 -5 Torr; preferably, the pressure of the nitrogen gas is 4 × 10⁻⁶. -5 Torr.

[0021] When the temperature of the Mg metal source is 350-360℃, the MgZnO thin film has a hexagonal crystal structure.

[0022] When the temperature of the Mg metal source is 365-370℃, the MgZnO thin film has a cubic crystal structure; preferably, when the temperature of the Mg metal source is 370℃, the MgZnO thin film has a cubic crystal structure.

[0023] The beneficial effects of this invention are:

[0024] (1) This invention innovatively achieves precise control of the MgZnO thin film crystal structure on the same substrate, fundamentally improving the technical defect that the thin film crystal structure can only be controlled by changing the substrate structure, simplifying the preparation process, shortening the production cycle, reducing substrate loss and process cost, and having stronger potential for industrial application.

[0025] (2) This invention achieves the controllable transformation of the crystal structure of MgZnO thin film by simply adjusting the temperature of the metal source and the angle of the doping element during the thin film growth process. According to experimental data, without N doping, the transformation of the thin film from a hexagonal structure to a cubic structure can be achieved simply by adjusting the Mg source temperature (360℃-380℃). After introducing N doping, the control effect can be further optimized, and the cubic structure transformation temperature can be reduced from 380℃ to 370℃, realizing the crystal structure switching at a lower temperature. This proves that the doping element and the metal source temperature can form a synergistic control effect, making the crystal structure control more precise and flexible, and meeting the differentiated needs of different application scenarios for thin film crystal structure.

[0026] (3) This invention effectively improves the crystal quality of MgZnO epitaxial films while achieving flexible control of crystal structure. Crystal quality is the core guarantee for the optical and electrical properties of thin film materials. Higher crystal quality can reduce the defect density inside the film, improve key properties such as carrier mobility and light transmittance, thereby expanding the application range of MgZnO films in optoelectronic devices, semiconductor devices and other fields, and improving the stability and reliability of devices based on this film.

[0027] (4) This invention clarifies the correlation between metal source temperature, doping elements, and the crystal structure of MgZnO thin films, and establishes a replicable and scalable method for controlling the crystal structure of epitaxial thin films. This method is not only applicable to MgZnO materials, but its core control ideas can also provide a reference for the crystal structure control of other similar compound semiconductor thin films, breaking the limitations of traditional control methods, enriching the technical means of thin film material preparation, and having great significance for promoting the technological development of the semiconductor thin film material field. Attached Figure Description

[0028] 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 only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0029] Figure 1 This is a flowchart illustrating the preparation process of the MgZnO thin film of this invention.

[0030] Figure 2 The image shows the X-ray diffraction pattern of the MgZnO thin film when the Mg source temperature is 350℃-380℃.

[0031] Figure 3 X-ray diffraction patterns of MgZnO thin films before and after N doping, with Mg source temperature of 360℃-370℃.

[0032] Figure 4 These are atomic model diagrams of two crystal structures. Detailed Implementation

[0033] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the 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.

[0034] Example 1

[0035] A method for controlling the crystal structure of grown thin films, the process flow diagram is as follows: Figure 1 As shown, by using a molecular beam epitaxy device, a zinc oxide buffer layer with low oxygen activity is first deposited on a cubic magnesium oxide (111) substrate by adjusting the metal source temperature and reducing oxygen activity. Then, a conventional low-temperature buffer layer is deposited, and then a zinc oxide thin film is grown. In this way, a zinc oxide single crystal thin film with good crystallinity and luminescence is prepared on a cubic substrate.

[0036] Specifically, the following steps are included:

[0037] (1) Using intact (111) magnesium oxide single crystal wafers with a surface size of 10mm×5mm×0.5mm, the wafers were cleaned three times each with acetone, alcohol, and deionized water to remove organic and inorganic matter from the sample surface. The wafers were then placed in a nitrogen-protected rapid injection chamber and evacuated for 1 hour using a vacuum device consisting of a mechanical pump and a turbomolecular pump to obtain 10 -8 After the Torr vacuum is applied, the sample is transferred to the growth chamber.

[0038] (2) After the sample was placed in the growth chamber, the magnesium oxide (111) substrate was heated to 490°C by molecular beam epitaxy and radiation heating in an oxygen atmosphere. A surface heat treatment was performed for 1 hour to remove surface defects and adsorbates. The oxygen pressure introduced was 5 × 10⁻⁶. -5 Torr, with an oxygen-activated plasma power of 250W.

[0039] (3) After the substrate is prepared, the zinc oxide buffer layer in the active oxygen is deposited. The oxygen radio frequency plasma is activated with a power of 200W. During the deposition process, the substrate temperature is maintained at 370℃, the oxygen pressure is 1×10-5 Torr, the zinc source temperature is 330℃, and the growth time is 10 minutes.

[0040] (4) After the buffer layer is grown, the MgZnO thin film is grown. At this time, the oxygen radio frequency plasma activation power is maintained at 250W, the substrate temperature is maintained at 400℃, and the oxygen pressure is 2×10⁻⁶. -5 Torr was used with a zinc source temperature of 330℃ and a Mg source temperature of 350℃. The growth time was 1.5 hours, and the sample was transferred out after growth was completed.

[0041] Example 2

[0042] A method for controlling the crystal structure of grown thin films, the process flow diagram is as follows: Figure 1 As shown, by using a molecular beam epitaxy device, a zinc oxide buffer layer with low oxygen activity is first deposited on a cubic magnesium oxide (111) substrate by adjusting the metal source temperature and reducing oxygen activity. Then, a conventional low-temperature buffer layer is deposited, and then a zinc oxide thin film is grown. In this way, a zinc oxide single crystal thin film with good crystallinity and luminescence is prepared on a cubic substrate.

[0043] Specifically, the following steps are included:

[0044] (1) Using intact (111) magnesium oxide single crystal wafers with a surface size of 10mm×5mm×0.5mm, the wafers were cleaned three times each with acetone, alcohol, and deionized water to remove organic and inorganic matter from the sample surface. The wafers were then placed in a nitrogen-protected rapid injection chamber and evacuated for 1 hour using a vacuum device consisting of a mechanical pump and a turbomolecular pump to obtain 10 -8 After the Torr vacuum is applied, the sample is transferred to the growth chamber.

[0045] (2) After the sample was placed in the growth chamber, the magnesium oxide (111) substrate was heated to 490°C by molecular beam epitaxy and radiation heating in an oxygen atmosphere. A surface heat treatment was performed for 1 hour to remove surface defects and adsorbates. The oxygen pressure introduced was 5 × 10⁻⁶. -5 Torr, with an oxygen-activated plasma power of 250W.

[0046] (3) After the substrate is prepared, the zinc oxide buffer layer in the active oxygen is deposited. The oxygen radio frequency plasma is activated with a power of 200W. During the deposition process, the substrate temperature is maintained at 370℃, the oxygen pressure is 1×10-5 Torr, the zinc source temperature is 330℃, and the growth time is 10 minutes.

[0047] (4) After the buffer layer is grown, the MgZnO thin film is grown. At this time, the oxygen radio frequency plasma activation power is maintained at 250W, the substrate temperature is maintained at 400℃, and the oxygen pressure is 2×10⁻⁶. -5 Torr was used with a zinc source temperature of 330℃ and a Mg source temperature of 360℃. The growth time was 1.5 hours, and the sample was transferred out after growth was completed.

[0048] Example 3

[0049] A method for controlling the crystal structure of grown thin films specifically includes the following steps:

[0050] (1) Using intact (111) magnesium oxide single crystal wafers with a surface size of 10mm×5mm×0.5mm, the wafers were cleaned three times each with acetone, alcohol, and deionized water to remove organic and inorganic matter from the sample surface. The wafers were then placed in a nitrogen-protected rapid injection chamber and evacuated for 1 hour using a vacuum device consisting of a mechanical pump and a turbomolecular pump to obtain 10 -8 After the Torr vacuum is applied, the sample is transferred to the growth chamber.

[0051] (2) After the sample was placed in the growth chamber, the magnesium oxide (111) substrate was heated to 490°C by molecular beam epitaxy and radiation heating in an oxygen atmosphere. A surface heat treatment was performed for 1 hour to remove surface defects and adsorbates. The oxygen pressure introduced was 5 × 10⁻⁶. -5 Torr, with an oxygen-activated plasma power of 250W.

[0052] (3) After the substrate is prepared, the zinc oxide buffer layer in the active oxygen is deposited. The oxygen radio frequency plasma is activated with a power of 200W. During the deposition process, the substrate temperature is maintained at 370℃, the oxygen pressure is 1×10-5 Torr, the zinc source temperature is 330℃, and the growth time is 10 minutes.

[0053] (4) After the buffer layer is grown, the MgZnO thin film is grown. At this time, the oxygen radio frequency plasma activation power is maintained at 250W, the substrate temperature is maintained at 400℃, and the oxygen pressure is 2×10⁻⁶. -5 Torr was used with a zinc source temperature of 330℃ and a Mg source temperature of 370℃. The growth time was 1.5 hours, and the sample was transferred out after growth was completed.

[0054] Example 4

[0055] A method for controlling the crystal structure of grown thin films specifically includes the following steps:

[0056] (1) Using intact (111) magnesium oxide single crystal wafers with a surface size of 10mm×5mm×0.5mm, the wafers were cleaned three times each with acetone, alcohol, and deionized water to remove organic and inorganic matter from the sample surface. The wafers were then placed in a nitrogen-protected rapid injection chamber and evacuated for 1 hour using a vacuum device consisting of a mechanical pump and a turbomolecular pump to obtain 10 -8 After the Torr vacuum is applied, the sample is transferred to the growth chamber.

[0057] (2) After the sample was placed in the growth chamber, the magnesium oxide (111) substrate was heated to 490°C by molecular beam epitaxy and radiation heating in an oxygen atmosphere. A surface heat treatment was performed for 1 hour to remove surface defects and adsorbates. The oxygen pressure introduced was 5 × 10⁻⁶. -5 Torr, with an oxygen-activated plasma power of 250W.

[0058] (3) After the substrate is prepared, a zinc oxide buffer layer in the active oxygen is deposited. Oxygen radio frequency plasma activation is turned on with a power of 200W. During the deposition process, the substrate temperature is maintained at 370℃ and the oxygen pressure is 1×10⁻⁶. -5 Torr, zinc source temperature 330℃, growth time 10 minutes;

[0059] (4) After the buffer layer is grown, the MgZnO thin film is grown. At this time, the oxygen radio frequency plasma activation power is maintained at 250W, the substrate temperature is maintained at 400℃, and the oxygen pressure is 2×10⁻⁶. -5 Torr was used with a zinc source temperature of 330℃ and a Mg source temperature of 380℃. The growth time was 1.5 hours, and the sample was transferred out after growth was completed.

[0060] Example 5

[0061] A method for controlling the crystal structure of grown thin films specifically includes the following steps:

[0062] (1) Using intact (111) magnesium oxide single crystal wafers with a surface size of 10mm×5mm×0.5mm, the wafers were cleaned three times each with acetone, alcohol, and deionized water to remove organic and inorganic matter from the sample surface. The wafers were then placed in a nitrogen-protected rapid injection chamber and evacuated for 1 hour using a vacuum device consisting of a mechanical pump and a turbomolecular pump to obtain 10 -8 After the Torr vacuum is applied, the sample is transferred to the growth chamber.

[0063] (2) After the sample was placed in the growth chamber, the magnesium oxide (111) substrate was heated to 490°C by molecular beam epitaxy and radiation heating in an oxygen atmosphere. A surface heat treatment was performed for 1 hour to remove surface defects and adsorbates. The oxygen pressure introduced was 5 × 10⁻⁶. -5 Torr, with an oxygen-activated plasma power of 250W.

[0064] (3) After the substrate is prepared, the zinc oxide buffer layer in the active oxygen is deposited. The oxygen radio frequency plasma is activated with a power of 200W. During the deposition process, the substrate temperature is maintained at 370℃, the oxygen pressure is 1×10-5 Torr, the zinc source temperature is 330℃, and the growth time is 10 minutes.

[0065] (4) After the buffer layer is grown, the MgZnO thin film is grown. At this time, the oxygen radio frequency plasma activation power is maintained at 250W, the substrate temperature is maintained at 400℃, and the oxygen pressure is 2×10⁻⁶. -5 Torr, nitrogen pressure 4 × 10 -5 Torr was used with a zinc source temperature of 330℃ and a Mg source temperature of 350℃. The growth time was 1.5 hours, and the sample was transferred out after growth was completed.

[0066] Example 6

[0067] A method for controlling the crystal structure of grown thin films specifically includes the following steps:

[0068] (1) Using intact (111) magnesium oxide single crystal wafers with a surface size of 10mm×5mm×0.5mm, the wafers were cleaned three times each with acetone, alcohol, and deionized water to remove organic and inorganic matter from the sample surface. The wafers were then placed in a nitrogen-protected rapid injection chamber and evacuated for 1 hour using a vacuum device consisting of a mechanical pump and a turbomolecular pump to obtain 10 -8 After the Torr vacuum is applied, the sample is transferred to the growth chamber.

[0069] (2) After the sample was placed in the growth chamber, the magnesium oxide (111) substrate was heated to 490°C by molecular beam epitaxy and radiation heating in an oxygen atmosphere. A surface heat treatment was performed for 1 hour to remove surface defects and adsorbates. The oxygen pressure introduced was 5 × 10⁻⁶. -5 Torr, with an oxygen-activated plasma power of 250W.

[0070] (3) After the substrate is prepared, the zinc oxide buffer layer in the active oxygen is deposited. The oxygen radio frequency plasma is activated with a power of 200W. During the deposition process, the substrate temperature is maintained at 370℃, the oxygen pressure is 1×10-5 Torr, the zinc source temperature is 330℃, and the growth time is 10 minutes.

[0071] (4) After the buffer layer is grown, the MgZnO thin film is grown. At this time, the oxygen radio frequency plasma activation power is maintained at 250W, the substrate temperature is maintained at 400℃, and the oxygen pressure is 2×10⁻⁶. -5 Torr, nitrogen pressure 4 × 10 -5 Torr was used with a zinc source temperature of 330℃ and a Mg source temperature of 360℃. The growth time was 1.5 hours, and the sample was transferred out after growth was completed.

[0072] Example 7

[0073] A method for controlling the crystal structure of grown thin films specifically includes the following steps:

[0074] (1) Using intact (111) magnesium oxide single crystal wafers with a surface size of 10mm×5mm×0.5mm, the wafers were cleaned three times each with acetone, alcohol, and deionized water to remove organic and inorganic matter from the sample surface. The wafers were then placed in a nitrogen-protected rapid injection chamber and evacuated for 1 hour using a vacuum device consisting of a mechanical pump and a turbomolecular pump to obtain 10 -8 After the Torr vacuum is applied, the sample is transferred to the growth chamber.

[0075] (2) After the sample was placed in the growth chamber, the magnesium oxide (111) substrate was heated to 490°C by molecular beam epitaxy and radiation heating in an oxygen atmosphere. A surface heat treatment was performed for 1 hour to remove surface defects and adsorbates. The oxygen pressure introduced was 5 × 10⁻⁶. -5 Torr, with an oxygen-activated plasma power of 250W.

[0076] (3) After the substrate is prepared, a zinc oxide buffer layer in the active oxygen is deposited. Oxygen radio frequency plasma activation is turned on with a power of 200W. During the deposition process, the substrate temperature is maintained at 370℃ and the oxygen pressure is 1×10⁻⁶. -5 Torr, zinc source temperature 330℃, growth time 10 minutes;

[0077] (4) After the buffer layer is grown, the MgZnO thin film is grown. At this time, the oxygen radio frequency plasma activation power is maintained at 250W, the substrate temperature is maintained at 400℃, and the oxygen pressure is 2×10⁻⁶. -5 Torr, nitrogen pressure 4 × 10 -5 Torr was used with a zinc source temperature of 330℃ and Mg source temperatures of 350℃, 360℃, 370℃, and 380℃, respectively. The growth time was 1.5 hours, and the samples were transferred out after growth was completed.

[0078] X-ray diffraction tests were performed on the samples prepared in Examples 1-7 at room temperature. The X-ray diffraction spectra revealed that the crystal structure of the epitaxial film was affected by the parameters during the growth process.

[0079] like Figure 2 As shown, in the undoped MgZnO sample, the film exhibits a hexagonal structure at Mg source temperatures of 350℃, 360℃, and 370℃, and a cubic structure at Mg source temperature of 380℃. The atomic models of the cubic (tetragonal) and hexagonal crystals are shown below. Figure 4 As shown.

[0080] like Figure 3 As shown, in the N-doped MgZnO sample, the film still has a hexagonal structure when the Mg source temperature is 350℃ and 360℃, but the film transforms into a cubic structure when the Mg source temperature is 370℃.

[0081] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. 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 controlling the structure of thin film crystals, characterized in that, Includes the following steps: (1) The surface of the cleaned magnesium oxide single crystal substrate is treated with oxygen plasma by molecular beam epitaxy and a zinc oxide buffer layer is grown. (2) Subsequently, molecular beam epitaxy was used to grow MgZnO thin films on the surface of magnesium oxide single crystal substrates; The process steps for growing MgZnO thin films are as follows: simultaneously introducing plasma-activated oxygen, a Zn metal source, and a Mg metal source to grow MgZnO thin films; and adjusting the temperature of the Mg metal source to make the crystal phase of the MgZnO thin film cubic or hexagonal.

2. The method for controlling the thin film crystal structure according to claim 1, characterized in that, The molecular beam epitaxy techniques in steps (1) and (2) are performed continuously within the same vacuum chamber.

3. The method for controlling the thin film crystal structure according to claim 2, characterized in that, The oxygen plasma treatment conditions are as follows: the temperature of the magnesium oxide single crystal substrate is 480-500℃, and the oxygen pressure is 4×10⁻⁶. -5 -6×10 -5 Torr, time is 0.5-2 hours.

4. The method for controlling the thin film crystal structure according to claim 3, characterized in that, The growth conditions for the zinc oxide buffer layer are as follows: the temperature of the magnesium oxide single crystal substrate is 390-410℃, the zinc source temperature is 320-340℃, and the oxygen pressure is 0.5×10⁻⁶. -5 -2×10 -5 Torr, growth time is 5-30 minutes.

5. The method for controlling the thin film crystal structure according to claim 4, characterized in that, The growth conditions for the MgZnO thin film in step (2) are as follows: the temperature of the magnesium oxide single crystal substrate is 365-375℃, the zinc source temperature is 325-335℃, the Mg source temperature is 350-380℃, and the oxygen pressure is 1×10⁻⁶. -5 -3×10 -5 Torr, growth time is 0.5-2 hours.

6. The method for controlling the thin film crystal structure according to claim 5, characterized in that, When the temperature of the Mg metal source is 350-370℃, the MgZnO thin film has a hexagonal crystal structure.

7. The method for controlling the thin film crystal structure according to claim 5, characterized in that, When the temperature of the Mg metal source is 375-380℃, the MgZnO thin film has a cubic crystal structure.

8. The method for controlling the thin film crystal structure according to claim 5, characterized in that, In step (2), nitrogen gas activated by plasma is introduced simultaneously with oxygen, a Zn metal source, and a Mg metal source to perform nitrogen doping treatment and obtain a nitrogen-doped MgZnO thin film; the pressure of the nitrogen gas is 3 × 10⁻⁶. -5 -5×10 -5 Torr.

9. The method for controlling the thin film crystal structure according to claim 8, characterized in that, When the temperature of the Mg metal source is 350-360℃, the MgZnO thin film has a hexagonal crystal structure.

10. The method for controlling the thin film crystal structure according to claim 8, characterized in that, When the temperature of the Mg metal source is 365-370℃, the MgZnO thin film has a cubic crystal structure.

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