Diamond / hexagonal boron nitride film heterostructure and preparation method thereof

Abstract

The invention discloses a heterostructure of a diamond / hexagonal boron nitride film and a preparation method of the heterostructure, and particularly relates to a method for growing the hexagonal boron nitride film by utilizing a magnetron sputtering method in a physical vapor deposition technology. According to the method, growth is carried out by accurately controlling parameters such as growth air pressure and sputtering power, the hexagonal boron nitride film which is high in quality, stable in performance and adjustable in film thickness is grown on the diamond substrate, the thickness of the hexagonal boron nitride film is adjustable from 20 nm to 600 nm, the hexagonal boron nitride film shows an E2g Raman peak, and covalent bonds are formed between the hexagonal boron nitride film and the surface of the diamond substrate. According to the method, the growth speed is high and controllable, the prepared film and the substrate are combined through covalent bonds, and a new strategy and thought are provided for synthesis and application of heterostructure materials.

Description

Technical Field

[0001] The invention belongs to the technical field of material preparation, and relates to a diamond / hexagonal boron nitride film heterostructure and a preparation method. Background Art

[0002] Both diamond and hexagonal boron nitride are wide bandgap semiconductor materials with excellent thermal conductivity, electrical insulation and chemical stability. They have broad application prospects in power electronic devices, high-voltage and high-frequency devices, optical windows and other fields.

[0003] Diamond has excellent properties such as wide band gap, high electron-hole mobility, low dielectric constant, superhardness, high thermal conductivity, radiation resistance, and good chemical stability. In a diamond crystal, each carbon atom is arranged in sp 3 The hybrid orbital forms a covalent bond with another four carbon atoms to form a regular tetrahedron, which is also called a cubic crystal structure. The surface of hydrogen-terminated diamond has p-type conductivity. The formation of two-dimensional vacancy gas on the surface of hydrogen-terminated diamond is related to the surface adsorption layer formed when exposed to air. The stability of the two-dimensional vacancy gas on the surface is poor because the surface adsorbent is difficult to control, resulting in unstable carrier transport performance.

[0004] Hexagonal boron nitride belongs to the hexagonal crystal system and has the same hexagonal crystal structure as graphite. It is stacked up in multiple layers, and different layers are connected by van der Waals forces. Due to its excellent performance, hexagonal boron nitride can be used as a protective layer for hydrogen-terminated diamond. Combining hexagonal boron nitride with diamond as a heterostructure can greatly improve the performance of diamond and broaden its application areas.

[0005] The existing heterostructure preparation scheme usually adopts the means of transfer. The two-dimensional atomic layer film of hexagonal boron nitride is transferred to the surface of the diamond substrate, which often introduces impurities, mechanical damage, wrinkles, poor repeatability, and is difficult to achieve large-scale preparation. The above problems can be solved by directly growing high-quality boron nitride films on the surface of diamond substrates. However, the direct growth of hexagonal boron nitride films on the diamond surface faces a series of challenges. The first is the control of nucleation and growth conditions. Different substrate materials have a great influence on the growth of hexagonal boron nitride films, which is related to the crystal structure, surface roughness and physicochemical properties of the substrate material (especially the thermal expansion coefficient and interface chemical bond composition of the film material and the substrate). Due to the large lattice mismatch between diamond and hexagonal boron nitride, stress may be generated in the film, causing the film to wrinkle or fall off the substrate. In addition, the growth of hexagonal boron nitride films on the diamond surface is mostly van der Waals epitaxial growth, that is, the two-dimensional layered grid of the hexagonal boron nitride film is stacked on the diamond surface, and the bonding force is weak, which may face the risk of peeling during the later device manufacturing.

[0006] In summary, there are still many technical challenges in the process of growing hexagonal boron nitride films on diamond, including film stability, film thickness regulation, and optimization of growth conditions. Therefore, exploring the optimal conditions for directly growing high-quality and stable hexagonal boron nitride films on diamond substrates is of great significance for improving the quality and performance of this heterostructure. Summary of the invention

[0007] In view of this, the purpose of the present invention is to overcome the deficiencies of the existing technical solutions and to provide a diamond / hexagonal boron nitride film heterostructure and a preparation method.

[0008] The technical solution of the present invention:

[0009] A diamond / hexagonal boron nitride film heterostructure is provided. Diamond is used as a substrate, and a hexagonal boron nitride film is grown on the substrate to form the diamond / hexagonal boron nitride film heterostructure.

[0010] In the diamond / hexagonal boron nitride film heterostructure, the thickness of the hexagonal boron nitride film is 20nm-600nm.

[0011] In the heterogeneous structure of the diamond / hexagonal boron nitride film, the hexagonal boron nitride film is covalently bonded to the surface of the diamond substrate.

[0012] A method for preparing a diamond / hexagonal boron nitride film heterostructure comprises the following steps:

[0013] (1) Diamond substrate treatment: Clean the diamond substrate and pre-treat its surface to obtain a surface roughness of less than 1 nm;

[0014] (2) Preparation of diamond / hexagonal boron nitride film heterostructure by magnetron sputtering: The diamond substrate obtained in step (1) was placed in a magnetron sputtering chamber and evacuated to a back-end vacuum of 1×10 -4 Pa, raise the temperature to 400-700 ° C, introduce argon and nitrogen as working gases, the introduction rate of argon is 10 ml / min, the introduction rate of nitrogen is 2-50 ml / min, so that the working gas pressure is 2Pa, the negative bias voltage is 10-120V, turn on RF sputtering to start depositing hexagonal boron nitride, the sputtering power is 60-170W, and the sputtering time is 2.5-120min.

[0015] In step (1), the diamond has a (100) crystal orientation.

[0016] In step (1), the cleaning process is that the diamond substrate is firstly ultrasonically cleaned, and acetone, alcohol and deionized water are used in sequence to remove grease and impurities on the surface.

[0017] In step (1), nitrogen and argon are introduced in advance for purge during vacuuming to improve the purity of the growing film.

[0018] In step (1), substrate pretreatment: In order to further ensure the surface state of the substrate, the diamond substrate is preheated to a certain temperature before sputtering, which helps to remove moisture and gas adsorbed on the surface and also helps the subsequent growth of the thin film.

[0019] In step (2), the nitrogen flow rate is 20 ml / min.

[0020] Beneficial effects of the present invention:

[0021] (1) The technical solution provided by the present invention can directly grow a hexagonal boron nitride film evenly and stably on the diamond surface to obtain a diamond / hexagonal boron nitride film heterostructure, thereby avoiding damage during the transfer process and surface and interface contamination caused by the transfer agent or solvent.

[0022] (2) The present invention adopts physical vapor deposition magnetron sputtering technology, which has a fast growth rate and can accurately control the thickness of the film by adjusting the growth parameters, achieving precise control of the thickness range from 20nm to 600nm, which provides flexibility for different application scenarios.

[0023] (3) The present invention adopts magnetron sputtering technology to grow a flat and stable hexagonal boron nitride film. By applying a negative bias voltage to the substrate during the growth process, a covalent bond is formed between the film and the substrate. This bonding method is stronger than the van der Waals force, which significantly improves the stability and adhesion of the hexagonal boron nitride film on the diamond substrate. Therefore, the hexagonal boron nitride film grown by this method can maintain long-term stability. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 This is the infrared spectrum of the heterostructure of the diamond / hexagonal boron nitride film prepared in Example 1.

[0025] Figure 2 This is a scanning image of the heterostructure of the diamond / hexagonal boron nitride film prepared in Example 1.

[0026] Figure 3 This is a scanning image of the heterostructure of the diamond / hexagonal boron nitride film prepared in Example 3.

[0027] Figure 4 This is the infrared spectrum of the heterostructure of the diamond / hexagonal boron nitride film prepared in Example 4. DETAILED DESCRIPTION

[0028] The specific implementation of the present invention is further described below in conjunction with the accompanying drawings and technical solutions.

[0029] Example 1

[0030] In this embodiment, the vacuum chamber is cleaned to ensure that there is no dust or impurities inside. The diamond substrate is placed on the sample stage in the sputtering chamber. The sputtering target is installed on the target position in the sputtering chamber. The vacuum pump is started to evacuate the back vacuum in the vacuum chamber to 1×10 -4 Pa, raise the temperature to the growth temperature of 700℃, introduce nitrogen and argon with a flow rate of 10ml / min respectively, adjust the working gas pressure to 2Pa, and the negative bias voltage to 120V. Set the sputtering power to 60W for thin film growth. Start the RF power supply, pre-sputter the target for 5 minutes, open the baffle, and start the formal sputtering growth process. After sputtering for 2 hours, pull up the baffle, turn off the RF power supply, and stop the sputtering process. Stop the introduction of nitrogen and argon, and slowly cool down. When the sample cools to room temperature, stop evacuating. Slowly release the pressure in the vacuum chamber to atmospheric pressure, take out the sample, and carry out subsequent characterization and analysis. Figure 1 This is the infrared transmission spectrum of the diamond / hexagonal boron nitride film heterostructure. It can be seen that in addition to the infrared active peak of the diamond substrate, there is also a 787cm -1 、1371cm -1 The absorption peaks at and correspond to the out-of-plane vibration of BNB in ​​h-BN and the in-plane vibration of BN, respectively.

[0031] Figure 2 This is a scanning electron microscope image of the hexagonal boron nitride film on the prepared heterostructure, showing that the thickness is 300 nm.

[0032] Example 2

[0033] In Example 1, other preparation conditions remain unchanged, and the growth time is changed to half an hour, and a heterostructure of the diamond / hexagonal boron nitride film similar to that in Example 1 can still be obtained. Figure 3 This is a scanning electron microscope image of the heterostructure of the prepared diamond / hexagonal boron nitride film. It can be seen that the film thickness is 20nm, indicating that this technology can achieve controllable film thickness by improving experimental parameters.

[0034] Example 3

[0035] In Example 1, other preparation conditions remain unchanged, and the sputtering power is changed to 150 W. A heterostructure of diamond / hexagonal boron nitride film similar to that in Example 1 can still be obtained. Figure 4 Infrared characterization of the heterostructure of the prepared diamond / hexagonal boron nitride film. There is a 1365cm -1 The absorption peak at 1586 cm corresponds to the in-plane vibration of BN in h-BN. -1 The absorption peaks at 1277 cm -1The absorption peak of the CN bond at . Infrared characterization shows that covalent bonds are formed between carbon and nitrogen, which means that the hexagonal boron nitride film and the diamond substrate are not just physically adsorbed or acted upon by van der Waals forces, but are bonded together by stronger covalent bonds. This bonding method can provide higher bonding strength and stability. By precisely controlling the growth conditions, high-quality interface bonding can be achieved, which is very important for improving device performance and stability.

[0036] Example 4

[0037] In Example 2, other preparation conditions remain unchanged, and the nitrogen flow rate is changed to 16 ml / min, and a diamond / boron nitride heterostructure similar to that in Example 2 can still be obtained.

[0038] Example 5

[0039] In Example 2, other preparation conditions remain unchanged, and the nitrogen flow rate is changed to 10 ml / min, and a heterostructure similar to a diamond / hexagonal boron nitride film can be obtained.

[0040] Example 6

[0041] In Example 2, other preparation conditions remain unchanged, and the negative bias voltage is changed to 10 V, and a heterostructure similar to a diamond / hexagonal boron nitride film can be obtained.

[0042] Example 7

[0043] In Example 2, other preparation conditions remain unchanged, and the negative bias voltage is changed to 120 V, and a heterostructure similar to a diamond / hexagonal boron nitride film can be obtained.

[0044] Comparative Example 1

[0045] In Example 1, other conditions remain unchanged, and the operating steps are the same as in Example 1. The sputtering power is changed to 50 W, the sputtering energy is reduced, the plasma concentration is reduced, C and N cannot form a bond at the interface between diamond and hexagonal boron nitride, and the above-mentioned stable diamond / hexagonal boron nitride film heterostructure cannot be obtained.

[0046] Comparative Example 2

[0047] In Example 1, the magnetron sputtering growth equipment is replaced with other equipment such as CVD, and the other steps are the same as Example 1. Since the CVD film growth process is slow and there is a saturation thickness, it is impossible to achieve a boron nitride film with controllable thickness.

[0048] Comparative Example 3

[0049] In Example 1, other conditions remain unchanged, the operating steps are the same as in Example 1, and no negative bias is set. C and N cannot form covalent bonds at the interface between diamond and hexagonal boron nitride, and the above-mentioned stable diamond / hexagonal boron nitride film heterostructure cannot be obtained.

[0050] The present invention relates to a diamond / hexagonal boron nitride film heterostructure and preparation method, and more particularly to a method for growing a hexagonal boron nitride film on a diamond substrate using a magnetron sputtering method in a physical vapor deposition technique, and is not limited to the specific experimental operations described in the specification and implementation methods. Therefore, any equivalent changes / variations or sequence changes made in accordance with the experimental parameters, operating procedures and principles described in the scope of the patent application of the present invention shall be included in the protection scope of the patent of the present invention.

Claims

1. A diamond / hexagonal boron nitride film heterostructure, characterized in that: Diamond is used as a substrate, and a hexagonal boron nitride film is grown on the substrate to form a diamond / hexagonal boron nitride film heterostructure.

2. The diamond / hexagonal boron nitride film heterostructure according to claim 1, characterized in that: In the diamond / hexagonal boron nitride film heterostructure, the thickness of the hexagonal boron nitride film is 20nm-600nm.

3. The diamond / hexagonal boron nitride film heterostructure according to claim 1, characterized in that: In the heterogeneous structure of the diamond / hexagonal boron nitride film, the hexagonal boron nitride film is covalently bonded to the surface of the diamond substrate.

4. A method for preparing a diamond / hexagonal boron nitride film heterostructure, characterized in that: The following steps are involved: (1) Diamond substrate treatment: Clean the diamond substrate and pre-treat its surface to obtain a surface roughness of less than 1 nm; (2) Preparation of diamond / hexagonal boron nitride film heterostructure by magnetron sputtering: The diamond substrate obtained in step (1) was placed in a magnetron sputtering chamber and evacuated to a back-end vacuum of 1×10 -4 Pa, raise the temperature to 400-700 ° C, introduce argon and nitrogen as working gases, the introduction rate of argon is 10 ml / min, the introduction rate of nitrogen is 2-50 ml / min, so that the working gas pressure is 2Pa, the negative bias voltage is 10-120V, turn on RF sputtering to start depositing hexagonal boron nitride, the sputtering power is 60-170W, and the sputtering time is 2.5-120min.

5. The preparation method according to claim 4, characterized in that: In step (1), the diamond has a (100) crystal orientation.

6. The preparation method according to claim 4, characterized in that: In step (1), the cleaning process is that the diamond substrate is firstly ultrasonically cleaned, and acetone, alcohol and deionized water are used in sequence to remove grease and impurities on the surface.

7. The preparation method according to claim 4, characterized in that: In step (1), nitrogen and argon are introduced in advance for purge during vacuuming to improve the purity of the growing film.

8. The preparation method according to claim 4, characterized in that: In step (1), substrate pretreatment: In order to further ensure the surface condition of the substrate, the diamond substrate is preheated before sputtering.

9. The preparation method according to claim 4, characterized in that: In step (2), the nitrogen flow rate is 20 ml / min.

Images