N-type diamond material and preparation method thereof

Abstract

The invention provides an N-type diamond material and a preparation method thereof, and belongs to the technical field of semiconductor materials. The lattice structure of the N-type diamond material comprises lithium atoms and nitrogen atoms, and the preparation method comprises the following steps: mixing an original diamond sheet with lithium carbonate powder, carrying out pressure annealing treatment to obtain lithium-injected diamond, and then carrying out N2 plasma treatment on the lithium-injected diamond to obtain lithium and nitrogen-injected diamond, and cooling the lithium and nitrogen injected diamond in liquid nitrogen to obtain the lithium and nitrogen injected diamond. The N-type semiconductor diamond stably exists at normal temperature and normal pressure, and a material foundation is laid for practical application of diamond electronic devices.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of semiconductor materials, and particularly relates to an N-type diamond material and a preparation method thereof. BACKGROUND

[0002] As the core engine of modern technological innovation, semiconductor technology is leading a material revolution in the field of power devices. Wide-bandgap semiconductor materials, with their unique physical properties, exhibit performance advantages far beyond traditional silicon-based materials: they not only have basic characteristics of high energy efficiency and low loss, but also can operate stably in harsh environments of high voltage (thousands of volts) and high temperature (above 300℃). The significant improvement in electron mobility and saturation rate enables the switch speed of devices to leap by orders of magnitude, greatly reduces the switching loss, and qualitatively improves the overall energy efficiency of the system. Especially in extreme working conditions, wide-bandgap devices show excellent adaptability - the loss can be reduced by 40% under the same charging conditions, and even in complex environments such as high temperature and radiation, the performance remains stable.

[0003] Among wide-bandgap materials, diamond has excellent chemical and physical properties, showing great potential in the field of electronics. Its ultra-wide bandgap, high carrier mobility, high thermal conductivity, and low dielectric constant make diamond an ideal choice for semiconductor devices operating in high-frequency, high-power, and high-temperature, high-pressure environments. Through doping technology, diamond can exhibit N-type and P-type conductivity, and its comprehensive performance far exceeds that of traditional materials such as GaAs, GaN, and SiC, earning it the reputation of "ultimate semiconductor". Despite the many advantages of diamond in the semiconductor field, its application still faces many challenges.

[0004] However, the industrialization process of diamond faces major challenges. Although P-type doping technology has made breakthroughs in the laboratory, the preparation of N-type diamond is still hindered by technical bottlenecks. Traditional dopants such as sulfur (S), phosphorus (P), and nitrogen (N) have not been able to obtain stable low-resistance N-type materials in injection experiments, with resistivity difficult to break through, carrier concentration and mobility far from theoretical expectations, and intrinsic problems such as low deep level impurity activation rate, high defect recombination center density, and high cost of single crystal preparation process, all of which hinder the large-scale application of diamond.

[0005] Therefore, the application provides a new type of N-type diamond material and a preparation method thereof. SUMMARY

[0006] To solve the above technical problems, the application provides an N-type diamond material and a preparation method thereof. Metal lithium (Li) is injected into diamond under pressure, and then co-doped with lithium (Li) and nitrogen (N) elements in a N2 plasma environment to realize the preparation of N-type diamond.

[0007] To achieve the above object, the present application provides the following technical solutions.

[0008] One of the technical solutions of the present application is:

[0009] A preparation method of the N-type diamond material, comprising the following steps:

[0010] The original diamond sheet is mixed with lithium carbonate powder, and after pressure annealing treatment, lithium-doped diamond is obtained, then the lithium-doped diamond is subjected to N2 plasma treatment to obtain lithium-nitrogen-doped diamond, and then the lithium-nitrogen-doped diamond is cooled in liquid nitrogen to obtain the N-type diamond material.

[0011] When the diamond is wrapped with lithium carbonate and subjected to pressure annealing treatment, the system obtains sufficient energy, and the temperature rise intensifies the thermal motion of atoms, and the presence of pressure provides the driving force for atomic migration. Under this condition, lithium ions in lithium carbonate become active and can overcome the diffusion energy barrier to escape and diffuse into the lattice of diamond. Since diamond has a specific crystal structure, lithium ions can occupy some interstitial positions or replace part of the positions of carbon atoms, thereby realizing the injection of lithium elements in diamond and obtaining lithium-doped diamond.

[0012] When the lithium-doped diamond is placed in an N2 plasma atmosphere, a voltage is applied to ionize N2. Under the action of the electric field, the chemical bonds in the N2 molecules are broken, and the molecules are decomposed into positively charged nitrogen ions (N⁺) and other charged particles. These charged particles have high energy and move towards the surface of the diamond under the action of the electric field force, and impact the surface of the diamond with a certain kinetic energy. Due to having sufficient energy, the nitrogen ions can overcome the potential barrier on the surface of the diamond and enter the lattice structure of the diamond, thereby realizing the injection of N elements through the surface of the diamond. The high temperature environment in the N2 plasma also intensifies the thermal motion of atoms, and the nitrogen atoms entering the surface of the diamond obtain sufficient energy and can diffuse in the lattice of the diamond. Thermal motion allows nitrogen atoms to migrate from areas with high concentration to areas with low concentration, thereby making the distribution of nitrogen elements in the diamond more uniform.

[0013] When the diamond is cooled to room temperature and placed in liquid nitrogen, the extremely low temperature of the liquid nitrogen causes the diamond to cool rapidly. This sharp temperature change generates a large thermal stress in the diamond, which causes a certain distortion of the diamond lattice, providing more favorable conditions for the further diffusion of nitrogen atoms. At the same time, low temperature can also inhibit some factors that are not conducive to the diffusion of nitrogen elements, reducing the activity of impurities or defects that hinder the migration of nitrogen atoms, thereby promoting the further penetration of N elements, and ultimately obtaining N-type diamond with specific lithium atom and nitrogen atom doping concentration.

[0014] Further, the average particle size of the lithium carbonate powder is 5 microns.

[0015] Further, the original diamond sheet is a single crystal diamond sheet or an N-doped conductive single crystal diamond sheet.

[0016] Further, the pressure annealing treatment is performed in spark plasma sintering (SPS), in which the sample is heated by pulse alternating current while pressure is applied, the temperature of the pressure annealing treatment is 200-600 DEG C, and the pressure is 1-50 MPa.

[0017] Further, the voltage of the N2 plasma treatment is 50-200 V, and the treatment time is 1-20 hours. During the N2 plasma treatment, N2 is ionized, and nitrogen elements are injected into the diamond.

[0018] Further, the diamond sheet further comprises a process of double-sided polishing before being mixed with the lithium carbonate powder.

[0019] The second technical solution of the present application is as follows:

[0020] An N-type diamond material is prepared according to the preparation method, the crystal lattice structure of the N-type diamond material contains lithium atoms and nitrogen atoms, and the N-type diamond material is a single crystal diamond.

[0021] Compared with the prior art, the present application has the following advantages and technical effects:

[0022] The diamond obtained by the present application is an N-type semiconductor diamond into which a certain amount of Li and N elements are injected. The present application breaks through the bottleneck of high-energy damage of traditional ion implantation, and constructs a stable coexistence structure of Li and N in the single crystal diamond through pressure annealing treatment, N2 plasma treatment and liquid nitrogen cooling process. Under the action of pressure-temperature conditions, not only the uniform distribution of doped particles and the lattice self-repair are promoted, but also the energy of doped atoms is lower than the desorption threshold through thermodynamic regulation, so that the N-type semiconductor diamond which stably exists at normal temperature and pressure is finally realized. The present application lays a material foundation for the practical application of diamond electronic devices. BRIEF DESCRIPTION OF DRAWINGS

[0023] The accompanying drawings, which form a part of the present application, are used to provide further understanding of the present application, and the illustrative embodiments of the present application and their description serve the purpose of explaining the present application, and do not constitute improper limitations on the present application. In the drawings:

[0024] Figure 1 The flow chart of the preparation method of the N-type diamond of the present application is shown in the figure.

[0025] Figure 2A process diagram for the process of cooling lithium, nitrogen-doped diamond into liquid nitrogen in Example 1, wherein a is a picture of lithium, nitrogen-doped diamond being immersed in liquid nitrogen, b is a picture of liquid nitrogen gradually evaporating, and c is a picture of the N-type diamond material obtained finally;

[0026] Figure 3 A high-resolution interface image of lithium-doped diamond prepared in Example 2;

[0027] Figure 4 A high-resolution image of lithium-doped diamond prepared in Example 2;

[0028] Figure 5 A picture of graphitized diamond material prepared in Comparative Example 3. DETAILED DESCRIPTION

[0029] The detailed description set forth below describes various illustrative embodiments of the application. Although described in the context of a particular implementation in a particular environment, the concepts are applicable to any system or method that implements the concepts.

[0030] It should be understood that the terms used herein are merely for describing particular embodiments and are not intended to limit the present application. In addition, for numerical ranges recited in the present application, it is contemplated that each intervening value, to the upper and lower limits of the ranges is also specifically disclosed. Each smaller range that falls within the integer ranges is also specifically disclosed. The upper and lower limits of these smaller ranges can independently be included or excluded in the range.

[0031] Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs. Although preferred methods and materials are described, any methods and materials similar or equivalent to those described herein can be used in the practice or testing of the present application. All documents mentioned herein are incorporated by reference to disclose and describe in further detail the methods and / or materials associated with the documents. In the case of conflict between the present specification and any document incorporated by reference, the present specification will control.

[0032] Various modifications and changes can be made to the specific implementation of the present application as described in the specification without departing from the scope or spirit of the application. Other implementations of the application will be apparent to those skilled in the art from consideration of the specification and practice of the application disclosed herein. The specification and examples given are exemplary and are not intended to be limiting.

[0033] As used herein, the terms "comprise", "comprising", "include", "including", "have", "having" and the like are open-ended and do not exclude additional elements or steps.

[0034] The embodiment of the present application provides an N-type diamond material, and a crystal lattice structure of the N-type diamond material comprises lithium atoms and nitrogen atoms.

[0035] In the preferred embodiment of the present application, the N-type diamond material is a single crystal diamond.

[0036] The embodiment of the present application further provides a preparation method of the N-type diamond material (a flow chart is shown in the figure) Figure 1 ), comprising the following steps:

[0037] The original diamond sheet is mixed with lithium carbonate powder, lithium injection diamond is obtained after pressure annealing treatment (heating under the action of pressure), then N2 plasma treatment is performed on the lithium injection diamond, lithium injection and nitrogen injection diamond is obtained, then the lithium injection and nitrogen injection diamond is cooled in liquid nitrogen, doping of elements Li and N is realized, and the N-type diamond material is obtained.

[0038] In the preferred embodiment of the present application, the diamond sheet is a single crystal diamond sheet or an N-doped conductive single crystal diamond sheet.

[0039] In the preferred embodiment of the present application, the pressure annealing treatment is performed in spark plasma sintering (SPS), the sample is heated by pulse alternating current, and pressure is applied at the same time, the temperature of the pressure annealing treatment is 200-600 DEG C, and the pressure is 1-50 MPa.

[0040] In the preferred embodiment of the present application, the voltage of the N2 plasma treatment is 50-200 V, and the treatment time is 1-20 h. In the N2 plasma treatment process, N2 is ionized, and then the nitrogen element is injected into the diamond.

[0041] In the preferred embodiment of the present application, before the original diamond sheet is mixed with lithium carbonate powder, the process of double-sided polishing is further included, and the diamond in the embodiment of the present application is a diamond that has been polished and polished. The specification of the single crystal diamond sheet and the N-doped conductive single crystal diamond is 5*5 mm or 7*7 mm, and the diamond used is a single crystal diamond prepared by an MPCVD method. First, a mixed gas of hydrogen (H2) and methane (CH4) is introduced into a cavity, and then the temperature is raised to 850 DEG C. Plasma power and cavity pressure jointly affect the ionization and decomposition of gas molecules, carbon atoms are continuously deposited and grown on the diamond substrate, and finally a diamond single crystal is obtained. The MPCVD method is a conventional technical method in the art, and the specific preparation process will not be described in detail.

[0042] In the preferred embodiment of the present application, the average particle size of the lithium carbonate powder is 5 microns, and the specific purchase manufacturer is Aladdin Biochemical Technology Co., Ltd.

[0043] In the preferred embodiment of the present application, the specific amount of raw material lithium carbonate powder and diamond is not limited, the diamond is calculated according to the piece, and the lithium carbonate wraps the diamond, and there is no strict mass ratio.

[0044] The raw materials used in the embodiment of the present application are commercially available.

[0045] In the embodiment of the present application, room temperature refers to “25±3℃”.

[0046] The technical solutions of the present application are further described below through examples.

[0047] Example 1

[0048] The carbon mill (specification: 10 mm in diameter and 5 mm in height cylinder) is added with lithium carbonate powder (average particle size: 5 μm) and single crystal diamond sheet after single piece polishing and polishing treatment, the single crystal diamond sheet is wrapped with lithium carbonate powder around, then pressure annealing treatment is carried out at 200℃ and 3 MPa to obtain lithium-injected diamond, and then N2 plasma treatment is carried out on the lithium-injected diamond in N2 plasma atmosphere, the voltage is set to 100 V, and the treatment time is 5 h, so as to further inject N element into the diamond to obtain lithium and nitrogen injected diamond, and the lithium and nitrogen injected diamond is cooled to room temperature and then put into liquid nitrogen for cooling (the process is shown in Figure 2 a-c in FIG. 1, wherein a is the picture of the lithium and nitrogen injected diamond immersed in liquid nitrogen, b is the picture of the gradual evaporation of liquid nitrogen, and c is the picture of the finally obtained N-type diamond material), so as to obtain N-type diamond material doped with lithium (Li) and nitrogen (N).

[0049] Example 2

[0050] The carbon mill (specification: 10 mm in diameter and 5 mm in height cylinder) is added with lithium carbonate powder (average particle size: 5 μm) and N-doped conductive single crystal diamond sheet after single piece polishing and polishing treatment, the N-doped conductive single crystal diamond sheet is wrapped with lithium carbonate powder around, then pressure annealing treatment is carried out at 400℃ and 1 MPa to obtain lithium-injected diamond, and then N2 plasma treatment is carried out on the lithium-injected diamond in N2 plasma atmosphere, the voltage is set to 80 V, and the treatment time is 10 h, so as to further inject N element into the diamond to obtain lithium and nitrogen injected diamond, and the lithium and nitrogen injected diamond is cooled to room temperature and then put into liquid nitrogen for cooling, so as to obtain N-type diamond material doped with lithium (Li) and nitrogen (N).

[0051] The high-resolution interface image of the lithium-injected diamond material prepared in Example 2 is shown in FIG. 2. Figure 3 The high-resolution image of the lithium-injected diamond prepared in Example 2 is shown in FIG. 3. Figure 4 It can be seen that there are diamond phase and amorphous phase at this time.

[0052] Example 3

[0053] Lithium carbonate powder (average particle size of 5 μm) and single piece polishing and polishing treatment of single crystal diamond piece were added in carbon grinding tool (specification: diameter of 10 mm, height of 5 mm cylinder), and the single crystal diamond piece was wrapped with lithium carbonate powder around the four corners. Then, pressure annealing treatment was carried out at 600℃ and 5 MPa to obtain lithium-injected diamond. Then, N2 plasma treatment was carried out in N2 plasma atmosphere, the voltage was set to 200 V, and the treatment time was 1 h. Further, N element was injected into the diamond to obtain lithium and nitrogen injected diamond. After the lithium and nitrogen injected diamond was cooled to room temperature, it was put into liquid nitrogen for cooling to obtain N-type diamond material doped with lithium (Li) and nitrogen (N).

[0054] Example 4

[0055] Lithium carbonate powder (average particle size of 5 μm) and N-doped conductive single crystal diamond piece after polishing and polishing treatment were added in carbon grinding tool (specification: diameter of 10 mm, height of 5 mm cylinder), and the N-doped conductive single crystal diamond piece was wrapped with lithium carbonate powder around the four corners. Then, pressure annealing treatment was carried out at 200℃ and 50 MPa to obtain lithium-injected diamond. Then, N2 plasma treatment was carried out in N2 plasma atmosphere, the voltage was set to 50 V, and the treatment time was 12 h. Further, N element was injected into the diamond to obtain lithium and nitrogen injected diamond. After the lithium and nitrogen injected diamond was cooled to room temperature, it was put into liquid nitrogen for cooling to obtain N-type diamond material doped with lithium (Li) and nitrogen (N).

[0056] Comparative Example 1

[0057] The traditional ion implantation method is to use high-energy ion beam to bombard the surface of the sample. The ion beam interacts with the solid material, and the speed of the ion gradually decreases due to the resistance of the solid material, and finally stays in the solid material.

[0058] In the above preparation process, the dopant (such as N, P) of diamond ion implantation will destroy the SP 3 structure of diamond, generate a large number of defects, which are difficult to repair by annealing, and the doping concentration distribution is uneven, and stable N-type diamond cannot be prepared.

[0059] Comparative Example 2

[0060] The same as Example 1, the difference is only that the step of putting into liquid nitrogen for cooling is omitted, which is as follows:

[0061] In a carbon die (specification: 10 mm in diameter and 5 mm in height cylinder), lithium carbonate powder (average particle size: 5 μm) and a single crystal diamond sheet subjected to single polishing and polishing treatment were added, the single crystal diamond sheet was wrapped with the lithium carbonate powder around the periphery, and then pressure annealing treatment was performed at 200°C and 3 MPa to obtain lithium-injected diamond, and then N2 plasma treatment was performed on the lithium-injected diamond in an N2 plasma atmosphere, the voltage was set to 100 V, and the treatment time was set to 5 h, and further N element was injected into the diamond to obtain lithium-nitrogen-injected diamond, and the lithium-nitrogen-injected diamond was cooled to room temperature to obtain N-type diamond material doped with lithium (Li) and nitrogen (N).

[0062] Comparative Example 3

[0063] The same as Example 1, except that the pressure annealing treatment was performed at 1000°C and 110 MPa.

[0064] Comparative Example 4

[0065] The same as Example 1, except that the voltage of the N2 plasma treatment was 300 V, and the treatment time was 9 h.

[0066] Performance Test

[0067] Test object: N-type diamond material prepared in Example 1

[0068] Test item and method: temperature-variable Hall test was performed at a test temperature of 30 K to verify that the diamond material prepared in Example 1 is N-type diamond, and the results are shown in Table 1.

[0069] Table 1

[0070] Carrier type N-type μ H ]]> Hall mobility [cm 2 / V s 30 n Carrier concentration [1 / cm 3 ]]]> 5*10 17 ]]>

[0071] The sample prepared in Comparative Example 2 was subjected to temperature-variable Hall test by the same method, and the results showed that the N-type characteristics of the diamond were unstable as the temperature increased. This indicates that the liquid nitrogen treatment of the doped diamond can further fix the doped N and Li particles, and prevent changes in ion concentration and doping position.

[0072] In Comparative Examples 3 and 4, whether the treatment temperature of the diamond is too high or the voltage of the plasma is too large, the diamond will undergo amorphization and graphitization, Figure 5 The picture of the graphitized diamond material prepared in Comparative Example 3 is shown in FIG. 2. Figure 5 As can be seen, once graphitization occurs, the lattice of the diamond is destroyed, and the SP 3 structure cannot be restored.

[0073] The above merely describes the preferred embodiments of the present application, but the protection scope of the present application is not limited thereto, and any person skilled in the art can easily think of changes or replacements within the technical scope disclosed by the present application, which should be covered in the protection scope of the present application. Therefore, the protection scope of the present application should be subject to the protection scope of the claims.

Claims

1. A method of producing an N-type diamond material, characterized by, The method comprises the following steps: The original diamond sheet is mixed with lithium carbonate powder, and after pressure annealing treatment, lithium-doped diamond is obtained, then the lithium-doped diamond is subjected to N2 plasma treatment to obtain lithium-nitrogen-doped diamond, and the lithium-nitrogen-doped diamond is cooled in liquid nitrogen to obtain the N-type diamond material.

2. The method of producing an N-type diamond material according to claim 1, wherein The average particle size of the lithium carbonate powder is 5 microns.

3. The method of producing an N-type diamond material according to claim 1, wherein The temperature of the pressure annealing treatment is 200-600 DEG C, and the pressure is 1-50 MPa.

4. The method of producing an N-type diamond material according to claim 1, wherein The voltage of the N2 plasma treatment is 50-200 V, and the treatment time is 1-20 hours.

5. The method of producing an N-type diamond material according to claim 1, wherein Before the original diamond sheet is mixed with lithium carbonate powder, the process of double-sided polishing is further included.

6. The method of producing an N-type diamond material according to claim 1, wherein The original diamond sheet is a single crystal diamond sheet or a nitrogen-doped conductive single crystal diamond sheet.

7. An N-type diamond material, characterised in that, The method is prepared according to any one of claims 1-6.

8. The N-type diamond material of claim 7, wherein, The N-type diamond material contains lithium atoms and nitrogen atoms in the crystal lattice structure, and the N-type diamond material is a single crystal diamond.

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