A conductive lanthanum aluminate / potassium tantalate heterostructure and its preparation method and application

Abstract

The present invention provides a conductive lanthanum aluminate / potassium tantalate heterostructure and a preparation method and application thereof. The preparation method comprises the following steps: placing a potassium tantalate substrate in a magnetron sputtering device, so that the angle between the surface to be coated of the potassium tantalate substrate and the normal line of the surface of the lanthanum aluminate target is 90°, the distance between the potassium tantalate substrate and the lanthanum aluminate target along the direction perpendicular to the substrate is 1.5 to 3.0 cm, and the distance between the potassium tantalate substrate and the lanthanum aluminate target along the direction perpendicular to the target is 3.5 to 5.5 cm; evacuating, opening the process valve to introduce argon gas, performing pre-sputtering, and then adjusting the argon gas pressure for sputtering to obtain a conductive lanthanum aluminate / potassium tantalate heterostructure. The preparation method of the present invention adjusts the relative position of the potassium tantalate substrate and the lanthanum aluminate target, and for the first time uses magnetron sputtering technology to prepare a lanthanum aluminate / potassium tantalate heterostructure with good conductivity at room temperature at a specific angle and distance.

Description

Technical Field

[0001] The present invention relates to the technical field of functional electronic materials, and in particular to a conductive lanthanum aluminate / potassium tantalate heterostructure and a preparation method and application thereof. Background Art

[0002] As a special oxide heterostructure, the field effect transistor characteristics of lanthanum aluminate / potassium tantalate are very close to the ideal field effect transistor. By adjusting the thickness of each material layer in the heterostructure or the overall conductivity, the response value of the prepared material and its corresponding device can be changed. In addition, compared with traditional silicon-based field effect transistors, lanthanum aluminate / potassium tantalate has become one of the popular choices for the preparation of future electronic devices due to its interface superconductivity, strong spin-orbit coupling, quantum Hall effect, etc.

[0003] At present, the methods for preparing lanthanum aluminate / potassium tantalate (LAO / KTO) heterostructures are usually pulsed laser deposition (PLD) and molecular beam epitaxy (MBE). This is mainly because LAO and KTO are both insulating materials. When the heterostructure is prepared at room temperature using the above-mentioned precision instruments, oxygen defects can be generated at the LAO / KTO interface, thereby making the LAO / KTO heterostructure conductive. However, since a higher gas pressure is usually required during magnetron sputtering, and this condition will cause the scattering of Al elements in the LAO target, the LAO / KTO heterostructure prepared by magnetron sputtering is usually in an insulating state and does not have conductivity. Summary of the invention

[0004] Based on this, it is necessary to provide a method for preparing a conductive lanthanum aluminate / potassium tantalate heterostructure by magnetron sputtering.

[0005] A method for preparing a conductive lanthanum aluminate / potassium tantalate heterostructure comprises the following steps:

[0006] Placing a potassium tantalate substrate in a magnetron sputtering device, so that the angle between the surface to be coated of the potassium tantalate substrate and the normal line of the surface of the lanthanum aluminate target is 90°, and the distance between the potassium tantalate substrate and the lanthanum aluminate target along a direction perpendicular to the substrate is 1.5 to 3.0 cm, and the distance between the potassium tantalate substrate and the lanthanum aluminate target along a direction perpendicular to the target is 3.5 to 5.5 cm;

[0007] The vacuum is evacuated, and the process valve is opened to introduce argon gas for pre-sputtering. Then, the argon gas pressure is adjusted for sputtering to obtain a conductive lanthanum aluminate / potassium tantalate heterostructure.

[0008] In one embodiment, the distance between the potassium tantalate substrate and the lanthanum aluminate target along a direction perpendicular to the substrate is 2 cm, and the distance between the potassium tantalate substrate and the lanthanum aluminate target along a direction perpendicular to the target is 3.5 cm.

[0009] In one embodiment, the target pressure of the vacuum step is 5×10 -4 Pa.

[0010] In one embodiment, the conditions of the pre-sputtering step are: electromagnetic power 40W, ignition gas pressure 3.5Pa, and pre-sputtering time 5 to 10 minutes.

[0011] In one embodiment, after the pre-sputtering step, the argon gas pressure is adjusted to 1 Pa for sputtering.

[0012] In one embodiment, the sputtering step is performed at room temperature and the sputtering time is 20 minutes.

[0013] In one embodiment, the purity of the argon gas is 5N.

[0014] In one embodiment, the magnetron sputtering equipment comprises a vacuum chamber, a substrate placing plate is provided on the top of the vacuum chamber, a sputtering target placing plate is provided on the bottom opposite to the substrate placing plate, a substrate fixing ruler is connected to the substrate placing plate, one end of the substrate fixing ruler away from the substrate placing plate extends in a direction perpendicular to the sputtering target placing plate; the potassium tantalate substrate is fixed on the substrate fixing ruler, and the lanthanum aluminate target is placed on the sputtering target placing plate.

[0015] The present invention also provides a conductive lanthanum aluminate / potassium tantalate heterostructure, which is prepared according to the above preparation method.

[0016] The present invention also provides the use of the conductive lanthanum aluminate / potassium tantalate heterostructure prepared by the above preparation method in the preparation of functional electronic devices.

[0017] The above solution of the present invention has the following beneficial effects:

[0018] The preparation method of the present invention adjusts the relative position of the potassium tantalate substrate and the lanthanum aluminate target, and uses magnetron sputtering technology for the first time at room temperature to prepare a lanthanum aluminate / potassium tantalate heterostructure with good conductivity at a specific angle and distance, thereby providing a new technical solution for preparing a conductive LAO / KTO oxide heterostructure, and at the same time providing a new idea for the large-scale production and application of oxide interfaces. Compared with the prior art (PLD and MBE), the preparation method has a short test cycle, is not affected by the spot size of the PLD laser beam, and can prepare samples of larger sizes. In addition, the technical solution also has the characteristics of easy operation, strong portability, strong universality, and applicability to large-scale production. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 This is a simplified example diagram of a conventional magnetron sputtering device;

[0020] Figure 2 This is a simplified example diagram of a magnetron sputtering device according to Embodiment 1 of the present invention;

[0021] Figure 3 A simplified example diagram of installing a potassium tantalate substrate in a magnetron sputtering device according to Example 1 of the present invention;

[0022] Figure 4 This is a temperature dependence curve of the conductive lanthanum aluminate / potassium tantalate heterostructure prepared in Example 1 of the present invention;

[0023] Figure 5 A simplified illustration of the magnetron sputtering device used in Comparative Example 1;

[0024] Figure 6 Sheet resistance test results of the samples prepared in Comparative Example 1;

[0025] Figure 7 A simplified illustration of the magnetron sputtering device used in Comparative Example 2;

[0026] Figure 8 Sheet resistance test results of the samples prepared in Comparative Example 2;

[0027] Fig. 9 A simplified illustration of a magnetron sputtering device used in Comparative Example 3;

[0028] Fig.10 This is the sheet resistance test result of the sample prepared in Comparative Example 3. DETAILED DESCRIPTION

[0029] In order to make the technical problems, technical solutions and advantages to be solved by the present invention clearer, the following will be described in detail with reference to the accompanying drawings and specific embodiments. Obviously, the described embodiments are part of the embodiments of the present invention, rather than all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0030] In addition, the technical features involved in the different embodiments of the present invention described below can be combined with each other as long as they do not conflict with each other.

[0031] At present, the methods for preparing lanthanum aluminate / potassium tantalate (LAO / KTO) heterostructures are usually pulsed laser deposition (PLD) and molecular beam epitaxy (MBE). However, since the sample size prepared by PLD depends on the spot size of the laser, it is not suitable for large-scale production. The use conditions of MBE are usually high vacuum state, and the experimental cycle is long, which is also not suitable for large-scale production. In addition, PLD and MBE are expensive, and the experimental cost and time cost are both high, so they are not universal. Due to the limitations of its own structure and the high gas pressure during the sputtering process, magnetron sputtering often causes large differences in the concentration of each element in the heterostructure prepared by sputtering. The element concentration is the key factor that causes oxygen defects in the heterostructure. Therefore, there is no precedent for using magnetron sputtering to prepare conductive LAO / KTO heterostructures at room temperature.

[0032] In view of the existing problems, the present invention provides a method for preparing a conductive lanthanum aluminate / potassium tantalate heterostructure, comprising the following steps:

[0033] S1. Place a potassium tantalate substrate in a magnetron sputtering device, so that the angle between the surface to be coated of the potassium tantalate substrate and the normal line of the surface of the lanthanum aluminate target is 90°, and the distance between the potassium tantalate substrate and the lanthanum aluminate target along the direction perpendicular to the substrate is 1.5 to 3.0 cm, and the distance between the potassium tantalate substrate and the lanthanum aluminate target along the direction perpendicular to the target is 3.5 to 5.5 cm.

[0034] S2, evacuate the chamber, open the process valve to introduce argon gas, perform pre-sputtering, and then adjust the argon gas pressure for sputtering to obtain a conductive lanthanum aluminate / potassium tantalate heterostructure.

[0035] The preparation method of the present invention adjusts the relative position of the potassium tantalate substrate and the lanthanum aluminate target, and uses magnetron sputtering technology for the first time at room temperature to prepare a lanthanum aluminate / potassium tantalate heterostructure with good conductivity at a specific angle and distance, thereby solving the problem of the non-conductivity of the LAO / KTO heterostructure caused by the small number of Al ions in the LAO film prepared by sputtering, providing a new technical solution for preparing conductive LAO / KTO oxide heterostructures, and providing a new idea for the large-scale production and application of oxide interfaces. Compared with traditional technologies (PLD and MBE), the preparation method has a short test cycle, is not affected by the spot size of the PLD laser beam, and can prepare larger-sized samples. In addition, the technical solution also has the characteristics of easy operation, strong portability, strong universality, and applicability to large-scale production.

[0036] Preferably, the distance between the potassium tantalate substrate and the lanthanum aluminate target along a direction perpendicular to the substrate is 2 cm, and the distance between the potassium tantalate substrate and the lanthanum aluminate target along a direction perpendicular to the target is 3.5 cm.

[0037] In a specific example, the target pressure of the vacuum step is 5×10 -4 Pa.

[0038] In a specific example, the conditions of the pre-sputtering step are: electromagnetic power 40W, ignition gas pressure 3.5Pa, pre-sputtering time 5 to 10 minutes, for example, 5, 6, 7, 8, 9, 10 minutes, etc.

[0039] In a specific example, after the above-mentioned pre-sputtering step, the argon gas pressure is adjusted to 1 Pa for sputtering.

[0040] In a specific example, the sputtering step is performed at room temperature for 20 minutes. It is understood that the range of room temperature is 25°C ± 5°C.

[0041] In a specific example, the purity of the argon gas is 5N, namely 99.999%, but is not limited thereto.

[0042] In a specific example, the dimensions of the potassium tantalate substrate are 3 mm×3 mm×0.5 mm.

[0043] In a specific example, the magnetron sputtering device has a vacuum chamber, a substrate placement plate is provided on the top of the vacuum chamber, a sputtering target placement plate is provided on the bottom opposite to the substrate placement plate, a substrate fixing ruler is connected to the substrate placement plate, and one end of the substrate fixing ruler away from the substrate placement plate extends in a direction perpendicular to the sputtering target placement plate; the potassium tantalate substrate is fixed on the substrate fixing ruler, and the lanthanum aluminate target is placed on the sputtering target placement plate. In this way, the existing magnetron sputtering device can be dismantled and modified to enable the relative positions of the potassium tantalate substrate and the lanthanum aluminate target to be adjusted to meet the requirements of the preparation method of the present invention, thereby facilitating the preparation of a conductive lanthanum aluminate / potassium tantalate heterostructure by magnetron sputtering at room temperature. It can be understood that the specific modification method of the magnetron sputtering device is not limited to this, as long as the relative positions of the potassium tantalate substrate and the lanthanum aluminate target can meet the preparation conditions of the present invention.

[0044] In a specific example, a target baffle is provided in the vacuum chamber of the magnetron sputtering device, and the target baffle is used to shield the target during pre-sputtering. Optionally, the substrate fixing ruler is made of steel.

[0045] The conductive lanthanum aluminate / potassium tantalate heterostructure of one embodiment of the present invention is prepared according to the above-mentioned preparation method.

[0046] The present invention also provides the use of the conductive lanthanum aluminate / potassium tantalate heterostructure prepared by the above preparation method in the preparation of functional electronic devices. Optionally, the above functional electronic devices include but are not limited to memristors, gas sensors, photoelectric devices, etc.

[0047] The present invention will be further described in detail below mainly in conjunction with specific implementation modes and drawings.

[0048] Example 1

[0049] like Figure 1 As shown, it is a simplified schematic diagram of a conventional magnetron sputtering device, wherein 1 is a vacuum chamber, 2 is a substrate placement plate, 3 is a substrate baffle, 4 is a sputtering target (lanthanum aluminate target), and 5 is a target baffle. In order to prepare the conductive lanthanum aluminate / potassium tantalate heterostructure, the substrate baffle 3 has been removed.

[0050] like Figure 2 As shown, the substrate fixing ruler 6 is bonded to the substrate placing plate 2, and the substrate fixing ruler 6 is perpendicular to the surface of the sputtering target 4, and the distance s between the substrate fixing ruler 6 and the sputtering target 4 in the horizontal direction is 2 cm. Figure 3 As shown, a potassium tantalate substrate 7 (3 mm×3 mm×0.5 mm) is placed at the position shown in the figure, so that the distance d between it and the sputtering target 4 along the direction perpendicular to the sputtering target 4 (ie, the vertical direction) is 3.5 cm.

[0051] The pressure in the vacuum chamber 1 was reduced to 5×10 -4 Pa, then open the process valve to 30%, introduce argon with a purity of 5N, the power is 40W, the ignition pressure is 3.5Pa, and pre-sputtering is performed for 6 minutes; adjust the argon pressure to 1Pa, open the target baffle 5 for sputtering coating, and the sputtering time is 20 minutes.

[0052] After the coating is completed, the equipment is normally closed and the sample is taken out, a Hall bar is made and the sheet resistance (R / □) of the sample is measured. The temperature dependence curve of the sample is measured using a comprehensive physical property measurement system (PPMS), such as Figure 4 As shown, it is demonstrated that the prepared lanthanum aluminate / potassium tantalate heterostructure has good metallic properties.

[0053] Comparative Example 1

[0054] Use Figure 5 The magnetron sputtering equipment shown is used to prepare a lanthanum aluminate / potassium tantalate heterostructure, and a potassium tantalate substrate (3 mm×3 mm×0.5 mm) is placed at positions 7A, 7B, 7C, and 7D on the surface of the substrate placement plate 2.

[0055] The pressure in the vacuum chamber 1 was reduced to 5×10 -4 Pa, then open the process valve to 30%, introduce argon with a purity of 5N, the power is 40W, the ignition pressure is 3.5Pa, and pre-sputtering is performed for 6 minutes; adjust the argon pressure to 1Pa, open the target baffle 5 for sputtering coating, and the sputtering time is 20 minutes.

[0056] After the coating is completed, the equipment is normally shut down and the sample is taken out. A Hall bar is made and the sheet resistance of the sample is measured. Figure 6 As shown, it can be seen that the prepared sample does not have good conductivity.

[0057] Comparative Example 2

[0058] Use Figure 7 The magnetron sputtering equipment shown in the figure prepares lanthanum aluminate / potassium tantalate heterostructures, and the substrate fixing ruler 6 is bonded to the substrate placing plate 2, and the substrate fixing ruler 6 is perpendicular to the surface of the sputtering target 4, and the distance between the substrate fixing ruler 6 and the sputtering target 4 in the horizontal direction is 2 cm. Potassium tantalate substrates 7 (3 mm×3 mm×0.5 mm) are placed at positions 7E, 7F, 7G, 7H, and 7I shown in the figure, and the distances d between them and the sputtering target 4 in the direction perpendicular to the sputtering target 4 (i.e., the vertical direction) are 4.0, 4.5, 5.0, 5.5, and 6.0 cm, respectively.

[0059] The pressure in the vacuum chamber 1 was reduced to 5×10 -4 Pa, then open the process valve to 30%, introduce argon with a purity of 5N, the power is 40W, the ignition pressure is 3.5Pa, and pre-sputtering is performed for 6 minutes; adjust the argon pressure to 1Pa, open the target baffle 5 for sputtering coating, and the sputtering time is 20 minutes.

[0060] After the coating is completed, the equipment is normally shut down and the sample is taken out. A Hall bar is made and the sheet resistance of the sample is measured. Figure 8 As shown, it can be seen that the conductivity of the prepared samples gradually becomes worse.

[0061] Comparative Example 3

[0062] Use Fig. 9 The magnetron sputtering equipment shown is used to prepare a lanthanum aluminate / potassium tantalate heterostructure. A substrate fixing ruler 6 is bonded to a substrate placing plate 2, and the substrate fixing ruler 6 is perpendicular to the surface of a sputtering target 4. The distance s between the substrate fixing ruler 6 and the sputtering target 4 along the horizontal direction is 1 cm, 1.5 cm, 2.5 cm, and 3.0 cm, respectively. Correspondingly, the potassium tantalate substrate 7 is placed at positions 7J (1 cm), 7K (1.5 cm), 7L (2.5 cm), and 7M (3.0 cm) as shown in the figure, respectively, and the distance between the substrate fixing ruler 6 and the sputtering target 4 along the direction perpendicular to the sputtering target 4 (i.e., the vertical direction) is 3.5 cm.

[0063] The pressure in the vacuum chamber 1 was reduced to 5×10 -4 Pa, then open the process valve to 30%, introduce argon with a purity of 5N, the power is 40W, the ignition pressure is 3.5Pa, and pre-sputtering is performed for 6 minutes; adjust the argon pressure to 1Pa, open the target baffle 5 for sputtering coating, and the sputtering time is 20 minutes.

[0064] After the coating is completed, the equipment is normally shut down and the sample is taken out. A Hall bar is made and the sheet resistance of the sample is measured. Fig.10 As shown, it can be seen that the conductivity of the prepared sample gradually increases and then decreases rapidly.

[0065] In summary, the present invention adjusts the relative position of the potassium tantalate substrate and the lanthanum aluminate target, and uses magnetron sputtering technology for the first time at room temperature to prepare a lanthanum aluminate / potassium tantalate heterostructure with good conductivity at a specific angle and distance. And this method has strong universality and can be applied to various types of magnetron sputtering equipment (including on-axis magnetron sputtering and off-axis magnetron sputtering) without being limited by the geometric structure of the equipment itself; it has strong portability and can be transplanted to various cases of preparing materials by magnetron sputtering in this field after simple modification; it is simple to operate, the technical threshold for use is low, and the input parameters are simple, clear and easy to understand; the output sample has high quality, good conductivity, low time and money costs, and is suitable for large-scale production.

[0066] The above is a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principles of the present invention. These improvements and modifications should also be regarded as the scope of protection of the present invention.

Claims

1. A method for preparing a conductive lanthanum aluminate / potassium tantalate heterostructure, characterized in that: The following steps are involved: Placing a potassium tantalate substrate in a magnetron sputtering device, so that the angle between the surface to be coated of the potassium tantalate substrate and the normal line of the surface of the lanthanum aluminate target is 90°, and the distance between the potassium tantalate substrate and the lanthanum aluminate target along a direction perpendicular to the substrate is 1.5-3.0 cm, and the distance between the potassium tantalate substrate and the lanthanum aluminate target along a direction perpendicular to the target is 3.5-5.5 cm; Evacuate the surface, open the process valve to introduce argon gas, perform pre-sputtering, and then adjust the argon gas pressure to perform sputtering to obtain the conductive lanthanum aluminate / potassium tantalate heterostructure; the sputtering step is performed at room temperature, and the range of room temperature is 25°C ± 5°C; The target pressure of the vacuum step is 5×10 -4 Pa; The conditions of the pre-sputtering step are: electromagnetic power 40W, ignition pressure 3.5Pa, pre-sputtering time 5-10 minutes; After the pre-sputtering step, the argon gas pressure was adjusted to 1 Pa for sputtering.

2. The method for preparing a conductive lanthanum aluminate / potassium tantalate heterostructure according to claim 1, characterized in that: The distance between the potassium tantalate substrate and the lanthanum aluminate target along a direction perpendicular to the substrate is 2 cm, and the distance between the potassium tantalate substrate and the lanthanum aluminate target along a direction perpendicular to the target is 3.5 cm.

3. The method for preparing a conductive lanthanum aluminate / potassium tantalate heterostructure according to claim 1, characterized in that: The splashing time is 20 minutes.

4. The method for preparing a conductive lanthanum aluminate / potassium tantalate heterostructure according to claim 1, characterized in that: The purity of the argon gas is 5N.

5. The method for preparing a conductive lanthanum aluminate / potassium tantalate heterostructure according to claim 1, characterized in that: The magnetron sputtering equipment comprises a vacuum chamber, a substrate placing plate is provided on the top of the vacuum chamber, a sputtering target placing plate is provided on the bottom opposite to the substrate placing plate, a substrate fixing ruler is connected to the substrate placing plate, one end of the substrate fixing ruler away from the substrate placing plate extends in a direction perpendicular to the sputtering target placing plate; the potassium tantalate substrate is fixed on the substrate fixing ruler, and the lanthanum aluminate target is placed on the sputtering target placing plate.

6. A conductive lanthanum aluminate / potassium tantalate heterostructure, characterized in that: Prepared according to the preparation method according to any one of claims 1 to 5.

7. Use of the conductive lanthanum aluminate / potassium tantalate heterostructure prepared by the preparation method according to any one of claims 1 to 5 in the preparation of functional electronic devices.

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