CN110724922B

CN110724922B - Epitaxial AZO film with controllable crystal orientation and polarity on flexible substrate and preparation method thereof

Info

Publication number: CN110724922B
Application number: CN201911052006.2A
Authority: CN
Inventors: 徐从康; 李永宽; 王江涌
Original assignee: Shantou University
Current assignee: Shantou University
Priority date: 2019-10-31
Filing date: 2019-10-31
Publication date: 2022-08-16
Anticipated expiration: 2039-10-31
Also published as: CN110724922A

Abstract

The invention relates to an epitaxial AZO film with controllable crystal orientation and polarity on a flexible substrate and a preparation method thereof, wherein the preparation method comprises the steps of (1) putting a high-temperature-resistant flexible substrate and a target material, which are composed of a nickel alloy base band and a textured buffer layer, into a vacuum chamber, vacuumizing, and heating the substrate; (2) introducing gas into the vacuum chamber through a flow controller; (3) and growing the AZO film by magnetron sputtering. The obtained flexible epitaxial AZO film: 1. the crystal orientation and the polarity are controllable, and the crystal comprises a polar epitaxial AZO (002) film, a non-polar epitaxial AZO (110) film and a polycrystalline AZO film; 2. the film has high conductivity ranging from 3 omega cm to 2E-5 omega cm; 3. the film grows on a high-temperature-resistant flexible substrate, is suitable for roll-to-roll large-scale industrial production, and has an applicable bending radius as low as 0.5 cm; 4. the film and the substrate are resistant to high temperature, and can resist the high temperature of 800 ℃ during preparation and application; 5. the film has transparency, and has a visible light transmittance of 80-95% when the film has a thickness of about 100nm and a roughness Rq of 1-5 cm.

Description

Epitaxial AZO film with controllable crystal orientation and polarity on flexible substrate and preparation method thereof

Technical Field

The invention belongs to the field of flexible semiconductor devices, and particularly relates to an epitaxial AZO film with controllable crystal orientation and polarity on a flexible substrate and a preparation method thereof.

Background

The ZnO material belongs to II-IV group semiconductors, has a forbidden band width of about 3.37eV at room temperature, exciton confinement energy as high as 60meV, is transparent to visible light, has good thermal conductivity, has outstanding carrier mobility, piezoelectric coefficient and luminous efficiency, is commonly applied to blue light ultraviolet light emitting diodes, transparent transistors, solar cells and high-power electric devices, and has very wide market prospect. The ZnO crystal is composed of oxygen atom sublattice and zinc atom sublattice, so that the polarity and the internal electric field in the c-axis direction are caused, and the electrical property and the photoelectric property of the material are obviously influenced. For example, while the nonpolar ZnO material has significantly higher luminous efficiency, the conductivity of the nonpolar ZnO film is anisotropic with respect to the uniform conductivity of the ZnO (002) film. Therefore, the polarity control is especially important when different ZnO electrical and photoelectric semiconductor devices are prepared. However, although there are various methods for producing ZnO thin films, such as magnetron sputtering, molecular beam epitaxy, thermal evaporation, chemical vapor deposition, etc., a polycrystalline zinc oxide thin film generally has a c-axis preferred orientation due to its low surface energy of (002) crystal plane, and an epitaxial ZnO single crystal thin film is more likely to have a (002) out-of-plane texture, and a non-polar, i.e., non- (002) out-of-plane texture ZnO thin film is more difficult to obtain.

The different doped ZnO is used for preparing transparent semiconductor materials with different conductivities, wherein AZO is an n-type semiconductor material. The conductivity and the transparency of the transparent electrode material of the heavily doped AZO semiconductor device are comparable to those of indium-doped tin oxide (ITO), but the indium element is rare, so that the AZO has a wider market prospect. AZO can be used as an electrode material of ZnO transparent electricity and photoelectric devices and can also be used as a substrate of high-quality epitaxial ZnO, so that the acquisition of an AZO thin film material with controllable crystal orientation and polarity is of great importance to the research and development of ZnO semiconductor devices.

In addition, the traditional semiconductor device is based on a thick wafer, so that the traditional semiconductor device is hard and brittle, the preparation process is complex, the production efficiency is low, and the traditional semiconductor device is only limited to planar application; the flexible device allows roll-to-roll large-scale industrial production, and has rapidly developed in recent years, and currently covers emerging application scenarios such as electronic skin for medical diagnosis, wearable functional equipment, flexible display, flexible solar cell, implantable micro-device and the like. Most of the existing flexible semiconductor devices are based on polymer and flexible glass substrates, the preparation and application occasions of the flexible semiconductor devices are limited by the lower melting point, burning point or glass transition temperature of substrate materials, and the substrate can rarely provide the basis of an epitaxial structure.

Therefore, the AZO film material with controllable crystal orientation and polarity and high quality directly grown on the flexible high-temperature-resistant substrate has great market prospect and application value.

Disclosure of Invention

The invention aims to provide an epitaxial AZO film with controllable crystal orientation and polarity on a flexible substrate and a preparation method thereof.

An epitaxial AZO film with controllable crystal orientation and polarity on a flexible substrate mainly comprises the following steps:

(1) placing a high-temperature-resistant flexible substrate consisting of a nickel alloy base band and a textured buffer layer and a target material into a vacuum chamber, vacuumizing, and heating the substrate;

(2) introducing gas into the vacuum chamber through a flow controller;

(3) and growing the AZO film by magnetron sputtering.

The nickel alloy base band is a flexible substrate band which is resistant to high temperature (can resist the high temperature of 800 ℃) and has the surface roughness Rq lower than 1 nm. Textured buffer layers, possessing cubic single crystal-like structures, have been fabricated on nickel alloy base ribbons and are flexible (bendable to bend radii of 0.5cm or less). The gas is a mixture of oxygen and other inert gases, and the proportion of the oxygen is 0-100 v.t%.

Preferably, the nickel alloy base band in the step (1) comprises hastelloy and a nickel-tungsten alloy.

Preferably, the textured buffer layer in step (1) includes one of magnesium oxide (MgO), Lanthanum Manganate (LMO), cerium oxide, titanium nitride, strontium titanate, or silicon nickel, and the crystal structure of the textured buffer layer is a cubic structure, including simple cube, face-centered cube, and body-centered cube. The AZO thin film grown on the specific textured buffer layer has specific polarity.

Preferably, the zinc oxide target material in step (1) includes an undoped zinc oxide target material with a purity higher than 99.9% or a zinc oxide target material doped with one or more of aluminum, indium, gallium, manganese, iron and nitrogen. In addition, modifications to the doping concentrations and sources are also included, such as using different aluminum doping concentrations, or doping targets with one or more of aluminum, indium, gallium, manganese, iron, and nitrogen.

Preferably, the temperature heated in the step (1) is 25-500 ℃, and the AZO film grown at a specific temperature has a specific crystal orientation.

Preferably, the gas in step (2) comprises argon and a mixed gas of argon and oxygen.

The epitaxial AZO film with controllable crystal orientation and polarity on the flexible substrate is prepared by the preparation method.

The epitaxial AZO film with controllable crystal orientation and polarity on the flexible substrate has the following characteristics: 1. the film comprises a polar epitaxial AZO (002) film, a non-polar epitaxial AZO (110) film and a polycrystalline AZO film, wherein crystal grains of the film have more than two out-of-plane orientations, including but not limited to AZO (002), AZO (100) and AZO (101); 2. the film has high conductivity ranging from 3 omega cm to 2E-5 omega cm. Wherein, AZO (002) film grown on the magnesium oxide substrate has the best conductivity, the repeatable and stable measured average value is about 1E-4 omega cm, the carrier mobility range is 1-30cm 3/V.s, the resistivity of other areas of the sample is measured in 5E-5 omega cm under special conditions, and the resistivity of the sample is reduced along with the temperature rise and is expressed as the semiconductor characteristic; 3. the film grows on a high-temperature-resistant flexible substrate, is suitable for roll-to-roll large-scale industrial production, and has an applicable bending radius as low as 0.5 cm; 4. the film and the substrate are resistant to high temperature, and can resist the high temperature of 800 ℃ during preparation and application; 5. the film has transparency, and has a visible light transmittance of 80-95% when the film has a thickness of about 100nm and a roughness Rq of 1-5 cm.

Compared with the prior art, the AZO film is prepared on the high-temperature-resistant flexible nickel alloy substrate, the magnetron sputtering method is adopted, the zinc oxide target material is sputtered and doped by using the mixed gas of inert gas and oxygen in different proportions, the crystal orientation and polarity of the AZO film are controlled by combining different substrate types and temperatures, the specific conductivity and the visible light transmittance are generated, the thickness of the film meets the flexibility requirement, and the obtained film has excellent crystallinity, conductivity, light transmittance and other photoelectric properties.

Drawings

FIG. 1 is a schematic diagram of a method for preparing an AZO thin film according to the present invention;

FIG. 2 is a high resolution X-ray diffraction pattern of a non-polar AZO film prepared on a flexible Hastelloy using a textured LMO buffer layer;

FIG. 3 is a {101} pole figure scan of a nonpolar AZO film prepared using a textured LMO buffer layer on a flexible Hastelloy;

FIG. 4 is a scanning electron microscope photograph of a non-polar AZO film prepared on a flexible Hastelloy using a textured LMO buffer layer;

FIG. 5 is a transmission electron micrograph (a) of a non-polar AZO film prepared on a flexible Hastelloy using a textured LMO buffer layer (b) taken electron beam diffraction spectra;

FIG. 6 is a resistivity-temperature curve for a non-polar AZO film prepared using a textured LMO buffer layer on a flexible Hastelloy;

FIG. 7 is a high resolution X-ray diffraction pattern of a polar AZO film prepared on a flexible Hastelloy using a textured MgO buffer layer;

FIG. 8 is a {101} pole figure scan of a polar AZO film prepared on flexible Hastelloy using a textured MgO buffer layer;

FIG. 9 is a scanning electron microscope photograph of a polar AZO film prepared on a flexible Hastelloy using a textured MgO buffer layer;

FIG. 10 is a transmission electron micrograph (a) of a polar AZO film prepared on a flexible Hastelloy using a textured MgO buffer layer and (b) a selected electron beam diffraction spectrum;

FIG. 11 is a resistivity-temperature curve for a polar AZO film made on a flexible Hastelloy using a textured MgO buffer layer;

FIG. 12 is a high resolution X-ray diffraction pattern of a polycrystalline AZO film prepared on a flexible Hastelloy using a textured MgO buffer layer;

FIG. 13 shows a scanning electron microscope photograph of a polycrystalline AZO film prepared on a flexible Hastelloy using a textured MgO buffer layer;

FIG. 14 is a high resolution X-ray diffraction pattern of a polycrystalline AZO film prepared using a textured LMO buffer layer on a flexible Hastelloy;

FIG. 15 shows a scanning electron microscope photograph of a polycrystalline AZO film prepared on a flexible Hastelloy using a textured LMO buffer layer;

FIG. 16 is a high resolution X-ray diffraction pattern of a polar AZO film prepared using argon oxygen gas mixture on a textured LMO buffer layer on a flexible Hastelloy;

figure 17 shows a scanning electron microscope photograph of a polar AZO film prepared using argon oxygen gas mixture on a flexible hastelloy using a textured LMO buffer layer.

Detailed Description

To make the objects, technical solutions and advantages of the present invention more apparent, the present invention will be described in further detail with reference to the accompanying drawings.

Example 1

A preparation method of an epitaxial AZO film with controllable crystal orientation and polarity on a flexible substrate is disclosed, as shown in figure 1, a flexible AZO film (3) is prepared on flexible nickel alloy substrates (1 and 2) with single-crystal-like simple cubic texture, a magnetron sputtering method is adopted, a zinc oxide target material (6) is sputtered and doped by using inert gas and oxygen mixed gas (4) in different proportions, the crystal orientation of the AZO film (3) is controlled by combining different substrate types and substrate temperatures (4), specific conductivity and visible light transmittance are generated, and the film thickness meets the flexibility requirement.

The specific implementation steps are as follows:

1. the clean flexible nickel alloy substrates (1 and 2) with the simple cubic texture buffer layer are placed on a sample rack of a vacuum chamber, an aluminum-doped zinc oxide target material (6) is placed on a magnetron sputtering target gun, and the vacuum is pumped to below 1E-3 Pa.

2. The substrate is heated by a heater to a target temperature (4) and held for a period of time to stabilize the temperature.

3. The vacuum chamber is fed with a target gas (5) via a mass flow controller.

4. And adjusting the pressure in the vacuum chamber, generating glow through a magnetron sputtering power supply, setting target power and carrying out pre-sputtering.

5. And opening a sample baffle or enabling the sample frame to face the target, and starting the deposition preparation of the AZO film (3).

6. And (4) closing the sputtering power supply, the gas and the heating power supply in sequence, deflating the vacuum chamber, taking out the sample, drying and storing.

7. The prepared AZO film is tested for the structure, optical and electrical characteristics by a high-resolution X-ray diffractometer (HRXRD), a field emission scanning electron microscope (FE-SEM), an Atomic Force Microscope (AFM), a high-resolution Transmission Electron Microscope (TEM), a Raman spectrometer (Raman), an ultraviolet-visible spectroscopy (UV-VIS), a photoluminescence spectrometer (PL), a step instrument, a four-probe tester (4probe setup) and a Hall tester (Hall setup).

In this embodiment, by changing the textured buffer layer, the substrate temperature, and the target gas on the flexible substrate, an epitaxial AZO film with controllable crystal orientation and polarity on the flexible substrate is obtained, and includes a polar epitaxial AZO (002) film, a non-polar epitaxial AZO (110) film, and a polycrystalline AZO film, i.e., crystal grains of the film have two or more out-of-plane orientations, including but not limited to AZO (002), AZO (100), and AZO (101), as shown in table 1.

TABLE 1 preparation method of AZO film with controllable crystal orientation

The AZO film has high conductivity ranging from 2E-1 omega-cm to 2E-5 omega-cm. Wherein, the (002) AZO film grown on the magnesium oxide substrate has the best conductivity, the repeatable and stable measurement average value is about 2.7E-4 omega cm, the carrier mobility range is 1-30cm 3/V.s, the resistivity of other areas of the sample is measured in 5E-5 omega cm under special conditions, and the resistivity of the sample decreases along with the temperature increase, thereby showing the semiconductor characteristic.

The film of the embodiment grows on a high-temperature-resistant flexible substrate, is suitable for roll-to-roll large-scale industrial production, and has an applicable bending radius as low as 0.5 cm;

the film and the substrate of the embodiment are resistant to high temperature, and can resist the high temperature of 800 ℃ during preparation and application;

the film of the present example has transparency, and has a visible light transmittance of 80% to 95% when the film has a thickness of about 100nm and a roughness Rq of 1 to 5 cm.

Example 2

A preparation method of a nonpolar AZO (110) film on a Hastelloy by epitaxy mainly comprises the following steps:

1. placing a clean Hastelloy substrate with a simple cubic texture buffer layer LMO on a vacuum chamber sample rack,and doping the aluminum with zinc oxide target (doping amount is more than that of Al) ₂ O ₃ ZnO is 2:98, purity 99.99%) is put on a magnetron sputtering target gun, and is vacuumized to below 1E-3Pa by using a mechanical pump and a molecular pump in a JPD500 magnetron sputtering system.

2. The substrate was heated to 300 ℃ by a resistance wire heater and held for a period of time to stabilize the temperature.

3. High purity argon (99.999% purity) was fed to the vacuum chamber through a mass flow controller.

4. The pressure in the vacuum chamber was adjusted by a flapper valve, a 50W rf power supply was used to generate a glow, and the power was increased stepwise to 160W for approximately 1h of pre-sputtering.

5. Rotating the sample holder to face the target material, and starting the AZO film deposition preparation, wherein the preparation time is 3 min.

7. The 2 theta-omega scan of the samples was performed by Bruker D8 ADVANCE type HRXRD and the results are shown in figure 2. On the c-axis oriented LMO, a (110) oriented AZO was obtained. The sample was scanned for ω and its out-of-plane texture Δ ω was measured to be about 2.36 °.

The ZnO {101} pologram of the sample was scanned by Bruker D8 ADVANCE type HRXRD, and the results are shown in FIG. 3. As a result, the {101} pole figure of the AZO film on the surface shows four-fold symmetry, which indicates that the film is composed of two groups of AZO (110) crystal grains with two-fold symmetry. Its in-plane texture Δ φ is about 5.90. And epitaxially growing the AZO film on the LMO buffer layer.

The film thickness was measured to be about 80nm using a Dektak XT type step meter. The surface morphology of the sample was characterized by a gemini FE-SEM, as shown in fig. 4. The prepared AZO film is flat and smooth, and has obvious crystal face and good crystallinity. The grain size is 30-100 nm. The film roughness Rq as measured by Dimension Icon AFM was 1.54nm, which is much lower than the polar AZO film roughness in example 3. The non-polar film is more suitable for optoelectronic devices.

The transmission electron micrograph and extracted electron beam diffraction spectrum of the sample were measured by a JEM-F200 TEM, and the results are shown in FIG. 5(a) and FIG. 5(b), respectively. The epitaxial relationship of the AZO film on the LMO buffer layer was obtained as (110) <100> AZO// (002) <200> LMO and (110) <002> AZO// (002) <200> LMO, with corresponding lattice mismatch levels of 0.26% and 7.74%, respectively. Referring to example 3, if polar AZO (002) is obtained on the LMO buffer layer, the epitaxial relationship of the film is (002) <110> AZO// (002) <200> LMO and (002) <100> AZO// (002) <200> LMO, the respective lattice mismatch degrees are 15.2% and 0.26%, respectively, much larger than that of the non-polar film. The film growth tends to minimize lattice mismatch to reduce film defects and stress. Therefore, the polarity of the AZO film on the Hastelloy in the epitaxial growth process can be controlled by adjusting the lattice constant of the buffer layer, namely adjusting the lattice mismatch degree.

The resistivity of the sample in the range of 300-500K tested by the Hall tester is shown in figure 6, which shows that the room temperature resistivity of the prepared AZO film is about 11E-4 omega-cm and shows the semiconductor characteristic, the resistivity decreases along with the rise of the testing temperature, and the resistivity at 500K is about 9.23E-5 omega-cm and shows higher conductivity, thus being more suitable for high temperature application. The low resistivity represents successful aluminum doping.

Example 3

A preparation method of a polar AZO (002) film on Hastelloy in an epitaxial manner mainly comprises the following steps:

1. placing a clean Hastelloy substrate with a simple cubic texture buffer layer MgO on a sample rack of a vacuum chamber, and doping aluminum with a zinc oxide target (the doping amount is more than that of Al) ₂ O ₃ ZnO is 2:98, purity 99.99%) is put on a magnetron sputtering target gun, and a JPD500 magnetron sputtering system is pumped to be vacuum below 1E-3Pa by using a mechanical pump and a molecular pump.

7. The 2 theta-omega scan of the samples was performed by Bruker D8 ADVANCE type HRXRD and the results are shown in figure 7. On the c-axis oriented MgO, a c-axis oriented AZO was obtained. The sample was scanned for ω and its out-of-plane texture Δ ω was measured to be about 2.38 °.

The ZnO {101} pologram of the sample was scanned by Bruker D8 ADVANCE type HRXRD, and the results are shown in FIG. 8. As a result, the ZnO {101} pole figure of the AZO film on the surface shows twelve points, which shows that the film is composed of two groups of zinc oxide with hexagonal structures, and the two groups of zinc oxide with hexagonal structures are typical epitaxial relations of crystals with hexagonal structures on crystals with tetragonal structures. Its in-plane texture Δ φ is about 4.66.

The film thickness was measured to be about 80nm using a Dektak XT type step meter. The surface morphology of the sample was characterized by a gemini FE-SEM, as shown in fig. 9. The prepared AZO film is flat and smooth, and has obvious crystal face and good crystallinity. The grain size is 20-50 nm. The film roughness Rq was measured by Dimension Icon AFM to be 4.60 nm.

The transmission electron micrograph and extracted electron beam diffraction spectrum of the sample were measured by a JEM-F200 TEM, and the results are shown in FIG. 10(a) and FIG. 10(b), respectively. The results show that the epitaxial relationship of the polar AZO film on the MgO buffer layer was (002) <110> AZO// (002) <200> MgO and (002) <100> AZO// (002) <200> MgO, with corresponding lattice mismatch levels of 9.10% and 5.52%, respectively, higher than the lattice adaptation of the non-polar AZO film in example 2. The preparation difficulty of the non-polar film is that the AZO (002) crystal face is more stable, so that the film tends to grow along the AZO (002) crystal face under the same lattice adaptation degree. In comparative example 2, the polarity of the epitaxial AZO film on hastelloy can be controlled by adjusting the lattice constant of the buffer layer, i.e. adjusting the lattice mismatch.

The resistivity of the sample in the range of 300-500K tested by the Hall tester is shown in FIG. 11, which shows that the prepared AZO film has the semiconductor characteristics, the room temperature resistivity is about 2.68E-4 omega-cm, and the resistivity at 500K is about 9.23E-5 omega-cm. The resistivity of the ITO film (thickness: about 180nm) on the standard glass was measured under the same conditions and was characterized as a metal, and the resistivity was 1.46E-4. omega. cm at room temperature and 1.65E-4. omega. cm at 500K. The polar AZO film is more suitable for being used as a transparent electrode material or preparing an electric device.

Example 4

A preparation method of a polycrystalline AZO film on Hastelloy mainly comprises the following steps:

2. The substrate was heated to 350 ℃ by a resistance wire heater and held for a period of time to stabilize the temperature.

4. The pressure in the vacuum chamber is adjusted through a baffle valve, a 50W radio frequency power supply is used for generating glow, the power is gradually increased to 160W, and the pre-sputtering is carried out for about 1 h.

5. Rotating the sample holder to face the target, and starting the AZO film deposition preparation, wherein the preparation time is 3 min.

7. The 2 theta-omega scan of the samples was performed by Bruker D8 ADVANCE type HRXRD and the results are shown in figure 12. The AZO film obtained in this example is a polycrystalline film whose out-of-plane orientation mainly includes (100), (002) and (101), in which there is a certain (002) preferred orientation, and the only parameter changed in the preparation method is the substrate temperature. In comparative example 1, the crystal orientation of the AZO thin film can be controlled by the substrate temperature.

The resistivity of the AZO film at normal temperature is measured to be 8.14E-4 omega cm by a Hall tester.

The surface morphology of the sample was characterized by a gemini FE-SEM, as shown in fig. 13. The surface of the prepared AZO film was similar to that of the AZO film obtained in example 1, since the c-axis of the film was preferentially oriented.

In comparative example 3, the crystal orientation of the AZO thin film can be controlled by releasing the stress of the epitaxial thin film through the substrate temperature.

Example 5

placing a clean Hastelloy substrate with a simple cubic texture buffer layer LMO on a sample holder of a vacuum chamber, and doping aluminum with a zinc oxide target (the doping amount is more than that of Al) ₂ O ₃ ZnO is 2:98, purity 99.99%) is put on a magnetron sputtering target gun, and a JPD500 magnetron sputtering system is pumped to be vacuum below 1E-3Pa by using a mechanical pump and a molecular pump.

2. The substrate was heated to 500 ℃ by a resistance wire heater and held for a period of time to stabilize the temperature.

7. The 2 theta-omega scan of the samples was performed by Bruker D8 ADVANCE type HRXRD and the results are shown in figure 14. The AZO film obtained in this example was a polycrystalline film whose out-of-plane orientation included mainly (100), (002) and (101), and the only parameters changed in the production method were the substrate temperature. As can be seen from comparative example 2, the crystal orientation of the AZO thin film can be controlled by the substrate temperature.

The resistivity of the AZO film at normal temperature is 3.22E-3 omega cm measured by a Hall tester.

The surface morphology of the sample was characterized by a gemini FE-SEM, as shown in fig. 15. The prepared AZO film is a polycrystalline film, so that the shape and the size of the crystal are not uniform, and the surface is rough.

In comparative example 2, the crystal orientation of the AZO thin film can be controlled by releasing the stress of the epitaxial thin film through the temperature of the substrate.

Example 6

A preparation method of a polar AZO (002) film on Hastelloy mainly comprises the following steps:

placing a clean LMO substrate with a single-crystal-like simple cubic texture on a sample holder of a vacuum chamber, and doping aluminum with a zinc oxide target (the doping amount is more than that of Al) ₂ O ₃ ZnO is 2:98, purity 99.99%) is put on a magnetron sputtering target gun, and is vacuumized to below 1E-3Pa by using a mechanical pump and a molecular pump in a JPD500 magnetron sputtering system.

3. A high purity argon oxygen mixture (oxygen ratio 50 v.t%, gas purity 99.999%) was fed to the vacuum chamber through a mass flow controller.

7. The 2 theta-omega scan of the samples was performed by Bruker D8 ADVANCE type HRXRD and the results are shown in figure 16. On the LMO buffer layer, a polar AZO (002) film was obtained. Comparative example 2 shows that the incorporation of more oxygen changes the lattice constant of the AZO film as it grows, and thus shows the polarity of the film. The polarity of the AZO film can be controlled by adjusting the lattice constant of the growth gas, namely the AZO film, so as to adjust the lattice mismatch.

The surface morphology of the sample was characterized by gemini FE-SEM, as shown in fig. 17. The prepared AZO film is flat and smooth, the crystal grain is circular, and the size of the crystal grain is 10-20 nm.

The AZO film has a resistivity of 2.57 omega cm at normal temperature measured by a Hall tester. When more oxygen exists in the growth gas, the conductivity of the film is obviously reduced, the film is closer to the conductivity of a semiconductor, and the method is suitable for preparing a pn junction. The result shows that the AZO film has controllable conductivity under different growth gas atmospheres, thereby laying a foundation for preparing corresponding electric and photoelectric devices.

Claims

1. A preparation method of a semipolar epitaxial AZO film on a flexible substrate is characterized by mainly comprising the following steps:

(1) placing a high-temperature-resistant flexible substrate consisting of a nickel alloy base band and a textured buffer layer and a target material into a vacuum chamber, vacuumizing, and heating the substrate, wherein the target material is an AZO target material with the purity higher than 99.9%, and the impurity doping amount ratio of Al ₂ O ₃ ZnO is 2: 98;

(2) introducing gas into the vacuum chamber through a flow controller, wherein the gas is argon;

(3) growing an AZO film by magnetron sputtering;

the textured buffer layer in the step (1) is one of MgO and LMO, and the crystal structure of the textured buffer layer is a simple cube;

when the textured buffer layer is MgO, the heating temperature in the step (1) is 400-450 ℃;

when the textured buffer layer is LMO, the heating temperature in the step (1) is 350-500 ℃;

the out-of-plane orientation of the semi-polar epitaxial AZO film is (100), (002), (101).

2. The method according to claim 1, wherein the nickel alloy base strip of step (1) comprises hastelloy and a nickel-tungsten alloy.

3. The semipolar epitaxial AZO thin film on the flexible substrate prepared by the preparation method according to claim 1.