Preparation method for green synthesis of boron nitride film based on elementary substance precursor

Abstract

The invention belongs to the technical field of boron nitride film preparation, and particularly relates to a preparation method of a green synthetic boron nitride film based on an elemental precursor. According to the method provided by the invention, N2 is adopted as a nitrogen source, boron powder is adopted as a boron source, a metal sheet subjected to annealing / chemical pretreatment is adopted as a catalytic substrate, and a double-temperature-zone controllable CVD furnace is used for preparing the boron nitride film. The method comprises the following steps: firstly, respectively placing a substrate and boron powder in two temperature zones of a CVD chamber, sealing and vacuumizing, and introducing carrier gas to recover normal pressure; and then setting the temperature, adjusting parameters such as introduced gas and the like, and completing the heating, annealing and growth stages of the two temperature zones. And after the growth is finished, stopping the temperature control program of the CVD equipment, naturally cooling the equipment, and accelerating the cooling speed of the boron powder and the substrate by using a fan in the stage. The N2 and the boron powder are used as the precursors, the common metal is used as the substrate, and the temperature of the precursor region and the temperature of the substrate region are separately controlled, so that the precursors can be fully activated, a proper temperature can be provided for growth of the boron nitride film, and the utilization rate of the precursors and the crystallization quality of the boron nitride film are improved. Other impurities or toxic substances are not introduced, the cost is low, the preparation process is simple, and meanwhile, the method is environment-friendly. The nitrogen source and the boron source are separately regulated and controlled, the growth process of the boron nitride film can be researched by virtue of isotopes, related mechanisms are analyzed, and certain reference is provided for subsequent research in the field.

Description

Technical Field

[0001] The present invention belongs to the technical field of electrocatalytic material preparation, and in particular relates to a method for preparing a green synthetic boron nitride film based on a single substance precursor. Background Art

[0002] Boron nitride has broad application prospects in the fields of electronics, energy, ceramics, coating materials, etc. due to its high thermal conductivity, high insulation, and high temperature resistance. Currently, the technical paths for the preparation of boron nitride films are divided into two categories: top-down and bottom-up. Top-down methods include mechanical exfoliation and liquid phase exfoliation, which destroy the van der Waals forces between bulk h-BN layers through physical or chemical methods to obtain a few-layer film. Its advantages are simple process and relatively high film quality. However, due to the limitations of exfoliation efficiency, product size, and uniformity, it is difficult to achieve large-scale uniform film preparation. Bottom-up methods include chemical vapor deposition (CVD), physical vapor deposition (PVD), and molecular beam epitaxy (MBE), which obtain h-BN films through atomic deposition and growth. Among them, the advantages of CVD are process controllability, strong compatibility, large film area, good uniformity, and relatively low equipment cost. It has become one of the mainstream methods for preparing large-area, high-quality h-BN films. The CVD method can control the nucleation density, nucleation direction, morphology, number of layers, and stacking structure by optimizing the precursors, substrate, and growth conditions, thereby achieving the preparation of h-BN with single or multilayer structures, smooth and uniform surfaces, polycrystalline or single crystals, and various stacking structures. However, traditional CVD methods for synthesizing h-BN often use organic precursors (such as NH3-BH3, B3N3H6, BCl3 / ethylmethylamine, etc.) as nitrogen and boron sources. This process is plagued by problems such as the introduction of carbon impurities, high precursor toxicity, complex reaction pathways, and numerous byproducts, which seriously restrict the quality of thin films and their large-scale application.

[0003] Therefore, how to prepare boron nitride films in a green and efficient manner remains a major challenge in the preparation of boron nitride films. Summary of the Invention

[0004] The present invention aims to address, at least to some extent, one of the technical problems in the related art. To this end, the present invention primarily aims to provide a method for preparing a green, synthetic boron nitride thin film based on a single precursor. The method provided by the present invention is not only environmentally friendly, but also has a low production cost and a simpler process.

[0005] The purpose of the present invention is achieved through the following technical solutions:

[0006] A method for preparing a green synthetic boron nitride film based on a single precursor comprises the following steps:

[0007] 1) Sample loading: Ar is introduced into the CVD chamber to bring the system from a low-pressure state to a normal pressure state. The substrate is placed on a quartz plate in the center of temperature zone 1. The boron powder loaded on the center of the quartz rack is placed in the center of temperature zone 2. The CVD chamber is then sealed.

[0008] 2) Vacuum treatment: After the chamber is sealed, turn on the vacuum pump to evacuate the sealed chamber. Turn off the vacuum pump after the air pressure drops to the ultimate vacuum that the system can achieve;

[0009] 3) Zone 1 Heating: Zone 1 heating stage: Ar is introduced again to change the CVD chamber from a low-pressure environment to a normal pressure environment. After the system reaches normal pressure, the outlet needle valve is opened to maintain the normal pressure environment. Set the temperature, introduce gas, set the gas flow rate, and then start the temperature control program for Zone 1 to heat up;

[0010] 4) Annealing in temperature zone 1 and preheating in temperature zone 2: When temperature zone 1 is heated to the specified temperature, annealing begins, and at this time, temperature zone 2 begins to heat up. The heating time of temperature zone 2 is consistent with the annealing time of temperature zone 1;

[0011] 5) Thin film growth: When the temperature in temperature zone 2 reaches the specified temperature, it enters the growth stage, and the growth time is adjusted according to the experimental conditions;

[0012] 6) Cooling: After the growth is completed, stop the temperature control program of temperature zone 1 and temperature zone 2, move the furnace out of the sample area, and use a fan to quickly cool the boron powder and substrate;

[0013] 7) Sample collection: After the boron powder and substrate cool to room temperature, turn off all gases, remove the sample, and then use a vacuum pump to evacuate the CVD chamber and store the system in a low-pressure state.

[0014] In certain specific embodiments, the substrate includes but is not limited to Cu foil, Ni foil, Cu-Ni alloy foil, Cu-Fe alloy foil, Fe-Ni alloy foil, Cu-Fe-Ni alloy foil.

[0015] Furthermore, the Cu foil and Ni foil are subjected to high-temperature annealing / electrochemical treatment to remove surface impurities; the alloy foil is prepared by electrochemical deposition combined with high-temperature annealing.

[0016] In certain specific embodiments, the temperature of the temperature zone 1 in step 3) is 800-1200° C., and the heating time of the temperature zone 1 is 0-2 h.

[0017] In certain specific embodiments, the gas introduced in step 3) includes one or more of Ar, H2, and O2, including but not limited to a mixture of any two of them, with a gas flow rate of 0-2000 sccm.

[0018] In certain specific embodiments, the temperature of the temperature zone 2 in step 4) is 800-1200° C., the heating time of the temperature zone 1 is 0-2 h; and the annealing time is 0-24 h.

[0019] In some specific embodiments, the temperature of the two temperature zones during the thin film growth stage in step 5) is 800-1200° C., and the time is 0-6 hours.

[0020] Compared with the prior art, the present invention has at least the following advantages:

[0021] 1) The preparation method of the present application uses elemental boron powder and N2 as reaction precursors, and common metal sheets such as Cu foil, Ni foil, etc. as substrates, which are low in cost and environmentally friendly.

[0022] 2) The preparation method of the present application first performs high-temperature annealing and electrochemical treatment on the substrate, which not only removes oxides and contaminants on the surface of the substrate, but also induces grain boundary migration to achieve grain growth. Increasing the grain size of the substrate can reduce the nucleation density of boron nitride and increase the crystal domain size of boron nitride.

[0023] 3) The preparation method of this application utilizes zoned temperature control, heating the substrate area and the precursor boron powder area separately. This ensures full activation of the precursor while providing an appropriate temperature for boron nitride film growth, improving precursor utilization and the crystallization quality of the boron nitride film. Furthermore, the corresponding temperature zone parameters can be adjusted according to the substrate type, enhancing process flexibility. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] In order to more clearly illustrate the specific embodiments of the present invention, the following briefly introduces the drawings required for the specific embodiments or the description of the prior art.

[0025] Figure 1 A schematic diagram of a device for preparing a boron nitride film according to an embodiment of the present invention;

[0026] Figure 2 This is an optical micrograph of the annealed copper substrate grown for 240 min in Example 1 of the present invention (scale bar: 10 μm) and a Raman spectrum of the black triangle area in the figure;

[0027] Figure 3 An optical micrograph of the nickel substrate grown in Example 2 of the present invention (scale bar: 10 μm) and a Raman spectrum of the circled area in the figure;

[0028] Figure 4 An optical micrograph of the Cu-Fe alloy substrate grown in Example 3 of the present invention (scale bar: 10 μm) and a Raman spectrum of the circled area in the figure;

[0029] Figure 5An optical micrograph of the Fe-Ni alloy substrate grown for 90 min in Example 4 of the present invention (scale bar: 10 μm) and a Raman spectrum of the circled area in the figure;

[0030] Figure 6 This is an optical micrograph of the Cu-Fe-Ni alloy substrate growth in Example 5 of the present invention (scale bar is 10 μm) and a Raman spectrum of the circled area in the figure. DETAILED DESCRIPTION

[0031] The present invention will be further described in detail below with reference to the accompanying drawings and examples. The following examples are merely illustrative and non-restrictive, and should not be used to limit the scope of protection of the present invention.

[0032] When expressing a certain amount, concentration or other value or parameter in the form of a range, preferred range, or preferred upper and lower numerical limits, it should be understood that it is equivalent to specifically disclosing any range by combining any pair of upper range limits or preferred numerical values with any lower range limit or preferred numerical value, without considering whether the range is specifically disclosed. Unless otherwise indicated, the numerical range values listed herein include the endpoints of the range and all integers and fractions within the range.

[0033] Unless otherwise indicated, all percentages, parts, ratios, etc. herein are by weight.

[0034] The materials, methods, and examples herein are illustrative and, unless otherwise indicated, are not to be construed as limiting.

[0035] The present invention provides a method for preparing a green synthetic boron nitride film based on a single substance precursor, comprising the following steps:

[0036] 1) Sample loading: Ar is introduced into the CVD chamber to bring the system from a low-pressure state to a normal pressure state. The substrate is placed on a quartz plate in the center of temperature zone 1. The boron powder loaded on the center of the quartz rack is placed in the center of temperature zone 2. The CVD chamber is then sealed.

[0037] 2) Vacuum treatment: After the chamber is sealed, turn on the vacuum pump to evacuate the sealed chamber. Turn off the vacuum pump after the air pressure drops to the ultimate vacuum that the system can achieve;

[0038] 3) Zone 1 Heating: Zone 1 heating stage: Ar is introduced again to change the CVD chamber from a low-pressure environment to a normal pressure environment. After the system reaches normal pressure, the outlet needle valve is opened to maintain the normal pressure environment. Set the temperature, introduce gas, set the gas flow rate, and then start the temperature control program for Zone 1 to heat up;

[0039] 4) Annealing in temperature zone 1 and preheating in temperature zone 2: When temperature zone 1 is heated to the specified temperature, annealing begins, and at this time, temperature zone 2 begins to heat up. The heating time of temperature zone 2 is consistent with the annealing time of temperature zone 1;

[0040] 5) Thin film growth: When the temperature in temperature zone 2 reaches the specified temperature, it enters the growth stage, and the growth time is adjusted according to the experimental conditions;

[0041] 6) Cooling: After the growth is completed, stop the temperature control program of temperature zone 1 and temperature zone 2, move the furnace out of the sample area, and use a fan to quickly cool the boron powder and substrate;

[0042] 7) Sample collection: After the boron powder and substrate cool to room temperature, turn off all gases, remove the sample, and then use a vacuum pump to evacuate the CVD chamber and store the system in a low-pressure state.

[0043] Wherein, the substrate includes but is not limited to Cu foil, Ni foil, Cu-Ni alloy foil, Cu-Fe alloy foil, Fe-Ni alloy foil, Cu-Fe-Ni alloy foil. In the technical solution of the present application, the substrate and the precursor boron powder are placed in different areas and the temperature control treatment is carried out in different areas. The reaction device used in the present invention is as follows Figure 1 As shown, the substrate is placed in the center of temperature zone 1, and boron powder is placed in the center of temperature zone 2. After being heated and fully volatilized, the boron powder is transported to the substrate area through the carrier gas and deposited on the substrate surface to form a boron nitride film.

[0044] The test methods used in the following examples are mainly:

[0045] 1) Optical microscopy analysis

[0046] The prepared boron nitride films were optically characterized using a Nikon Eclipse LV100ND optical microscope;

[0047] 2) Raman spectroscopy analysis

[0048] The prepared boron nitride film was subjected to Raman spectroscopy analysis using a Renishaw Invia Reflex Raman spectrometer. The laser wavelength used in the Raman test was 532 nm and the laser power was 1.5 MW.

[0049] Example 1

[0050] Annealed copper foil was used as the substrate, and N2 and 200mg of boron powder were used as the precursors. The specific copper foil annealing process is as follows: First, the copper foil is placed in the constant temperature zone of the CVD chamber. After the chamber is sealed, the vacuum pump is turned on to evacuate the sealed chamber. Then, Ar is introduced to restore the CVD chamber to atmospheric pressure. The outlet needle valve is opened to maintain atmospheric pressure, and the program is started. The temperature is heated to 1050°C within 40 minutes and maintained at this temperature for 6 hours. The gas flow rate is adjusted to 100 sccm Ar and 20 sccm H2. After the annealing is completed, the sample is removed after the system cools naturally to room temperature.

[0051] Temperature zone 1 heating stage (0-60min): Temperature zone 1 is heated from room temperature to 1050°C, and N2 (100sccm) and H2 (5sccm) are introduced at the same time to form an inert reducing atmosphere; Annealing and temperature zone 2 preheating stage (60-90min): The gas composition remains unchanged, temperature zone 1 is maintained at 1050°C to anneal the copper substrate, and temperature zone 2 is simultaneously heated to 950°C to heat the boron powder; Growth stage (t=240min): The two temperature zones are stabilized at 1050°C (substrate zone) and 950°C (precursor zone) respectively to ensure continuous transport of boron-nitrogen species to the substrate surface; Cooling stage: Turn off the heating power supply, keep the gas conditions unchanged, and cool naturally to room temperature.

[0052] Example 2

[0053] Nickel foil was used as the substrate, and N2 and 60mg of boron powder were used as precursors. The boron nitride film growth process included the following steps: Zone 1 ramp phase (0-65 minutes), with the temperature in Zone 1 increasing from 20°C to 1100°C using N2 (100 sccm) and H2 (20 sccm); Zone 1 annealing and Zone 2 ramp phase (65-95 minutes), with Zone 1 maintained at 1100°C and Zone 2 ramped from 20°C to 950°C using N2 (100 sccm) and H2 (20 sccm); the growth phase (95-185 minutes), with Zone 1 maintained at 1100°C and Zone 2 maintained at 950°C using N2 (100 sccm) and H2 (40 sccm); and the cooling phase, with N2 (100 sccm) and H2 (40 sccm).

[0054] Example 3

[0055] A Cu-Fe alloy foil is used as the substrate, and N2 and 200mg of boron powder are used as precursors. The Cu-Fe alloy foil is obtained by electrochemical deposition of copper foil combined with a high-temperature annealing process. Before electroplating, the copper foil is electrochemically polished on both sides using a solution of ethylene glycol and phosphoric acid in a ratio of 1:3 to remove impurities and improve the flatness of the foil. The foil is then dried with nitrogen before use.

[0056] The Cu-Fe alloy foil was prepared by electrochemical iron plating. The specific operation was as follows: the iron plating solution was: 560g nickel sulfate hexahydrate, 16g nickel chloride hexahydrate, 8g sodium fluoride and 60g boric acid dissolved in 2L deionized water. Polyimide tape was used to fix the bottom and both sides of the polished Cu foil to the PET to prevent the plating solution from penetrating between the Cu foil and the PET. The electroplated Cu foil was used as the cathode and the Fe foil was used as the anode. The regulated DC power supply was set to constant current mode with a current density of 0.01A / cm 2 The electroplating time was 45 minutes. After the electroplating was completed, the Cu-Fe alloy foil was washed with deionized water to remove the residual plating solution on the surface, and finally its surface was blown dry with N2. After the Cu-Fe alloy foil was turned over, the above fixing steps were repeated to ensure that the back side was tightly fitted with the PET substrate. The reverse side electroplating was completed under the same current density conditions and electroplating time, and then washed with deionized water and blown dry with N2. After the double-sided electroplating was completed, the electroplated Cu-Fe alloy foil was placed in acetone, anhydrous ethanol and deionized water for cleaning to further remove the residual plating solution on the surface, and finally its surface was blown dry with N2.

[0057] A Cu-Fe alloy foil was subjected to high-temperature annealing to reduce surface roughness. The following steps were performed: The foil was first placed in the constant temperature zone of a CVD chamber. After the chamber was sealed, a vacuum pump was activated to evacuate the sealed chamber. Ar was then introduced to return the CVD chamber to atmospheric pressure, and the outlet needle valve was opened to maintain atmospheric pressure. 600 sccm of Ar and 40 sccm of H₂ were introduced throughout the process. The process was initiated, heating to 1050°C over 70 minutes, followed by annealing for 6 hours. After the process was completed, the sample was removed after the system cooled naturally to room temperature.

[0058] Temperature zone 1 heating stage (0-65min), the temperature of temperature zone 1 is increased from 20℃ to 1050℃, and the gases are N2 (100sccm) and H2 (5sccm); Temperature zone 1 annealing, temperature zone 2 heating stage (65-95min), the temperature of temperature zone 1 is maintained at 1050℃, and the temperature of temperature zone 2 is increased from 20℃ to 950℃, and the gases are N2 (100sccm) and H2 (5sccm); Growth stage (95-275min), the temperature of temperature zone 1 is maintained at 1050℃, the temperature of temperature zone 2 is maintained at 950℃, and the gases are N2 (100sccm) and H2 (5sccm); Cooling stage, the gases are N2 (100sccm) and H2 (5sccm).

[0059] Example 4

[0060] An Fe-Ni alloy foil was used as the substrate, and N2 and 200 mg of boron powder were used as precursors. The Fe-Ni alloy foil was obtained by electrochemical deposition of iron foil combined with a high-temperature annealing process. The specific operation was the same as in Example 3, wherein the nickel electroplating solution was 560 g of nickel sulfate hexahydrate, 16 g of nickel chloride hexahydrate, 8 g of sodium fluoride, and 60 g of boric acid dissolved in 2 L of deionized water.

[0061] Temperature zone 1 heating stage (0-65min), the temperature of temperature zone 1 is increased from 20℃ to 1100℃, and the gases are N2 (100sccm) and H2 (5sccm); Temperature zone 1 annealing, temperature zone 2 heating stage (65-95min), the temperature of temperature zone 1 is maintained at 1100℃, and the temperature of temperature zone 2 is increased from 20℃ to 950℃, and the gases are N2 (100sccm) and H2 (5sccm); Growth stage (90min), the temperature of temperature zone 1 is maintained at 1100℃, the temperature of temperature zone 2 is maintained at 950℃, and the gases are N2 (100sccm) and H2 (5sccm); Cooling stage, the gases are N2 (100sccm) and H2 (5sccm).

[0062] Example 5

[0063] Cu-Fe-Ni alloy foil was used as the substrate, and N2 and 200mg of boron powder were used as precursors. The Cu-Fe-Ni alloy foil was obtained by electrochemical deposition of copper foil combined with high-temperature annealing. The specific operation was the same as in Example 3.

[0064] In the heating stage of temperature zone 1 (0-65min), the temperature of temperature zone 1 is increased from 20°C to 1100°C, and the gases are Ar (100sccm) and Ar / O2 (2sccm); in the annealing stage of temperature zone 1 (65-275min) and the heating stage of temperature zone 2 (245-275min), the temperature of temperature zone 1 is maintained at 1100°C, and the temperature of temperature zone 2 is increased from 20°C to 950°C, and the gases are N2 (100sccm) and Ar / O2 (2sccm); in the growth stage (275-365min), the temperature of temperature zone 1 is maintained at 1100°C, and the temperature of temperature zone 2 is maintained at 950°C, and the gases are N2 (100sccm) and H2 (40sccm); in the cooling stage, the gases are N2 (100sccm) and H2 (40sccm).

[0065] The above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit the same. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some or all of the technical features therein. These modifications or replacements do not deviate the essence of the corresponding technical solutions from the scope of the technical solutions of the embodiments of the present invention, and they should all be included in the scope of the claims and description of the present invention.

Claims

1. A method for preparing a green synthetic boron nitride film based on a single precursor, characterized in that: The steps include: 1) Sample loading: Ar is introduced into the CVD chamber to bring the system from a low-pressure state to a normal pressure state. The substrate is placed on a quartz plate in the center of temperature zone 1. The boron powder loaded on the center of the quartz rack is placed in the center of temperature zone 2. The CVD chamber is then sealed. 2) Vacuum treatment: After the chamber is sealed, turn on the vacuum pump to evacuate the sealed chamber. Turn off the vacuum pump after the air pressure drops to the ultimate vacuum that the system can achieve; 3) Zone 1 Heating: Zone 1 heating stage: Ar is introduced again to change the CVD chamber from a low-pressure environment to a normal pressure environment. After the system reaches normal pressure, the outlet needle valve is opened to maintain the normal pressure environment. Set the temperature, introduce gas, set the gas flow rate, and then start the temperature control program for Zone 1 to heat up; 4) Annealing in temperature zone 1 and preheating in temperature zone 2: When temperature zone 1 is heated to the specified temperature, annealing begins, and at this time, temperature zone 2 begins to heat up. The heating time of temperature zone 2 is consistent with the annealing time of temperature zone 1; 5) Thin film growth: When the temperature in temperature zone 2 reaches the specified temperature, it enters the growth stage, and the growth time is adjusted according to the experimental conditions; 6) Cooling: After the growth is completed, stop the temperature control program of temperature zone 1 and temperature zone 2, move the furnace out of the sample area, and use a fan to quickly cool the boron powder and substrate; 7) Sample collection: After the boron powder and substrate cool to room temperature, turn off all gases, remove the sample, and then use a vacuum pump to evacuate the CVD chamber and store the system in a low-pressure state.

2. The method according to claim 1, characterized in that The substrate includes but is not limited to the following metal sheets: copper (Cu) foil, nickel (Ni) foil, copper-nickel (Cu-Ni) alloy foil, copper-iron (Cu-Fe) alloy foil, iron-nickel (Fe-Ni) alloy foil, copper-iron-nickel (Cu-Fe-Ni) alloy foil.

3. The method according to claim 2, characterized in that The copper foil and nickel foil are subjected to high-temperature annealing / electrochemical treatment to remove surface impurities; the alloy foil is prepared by electrochemical deposition combined with high-temperature annealing process.

4. The method according to claim 1, wherein The temperature of temperature zone 1 is 800-1200°C, and the heating time of temperature zone 1 is 0-2h.

5. The method according to claim 1, wherein The temperature of temperature zone 2 is 800-1200℃, and the heating time of temperature zone 1 is 0-2h.

6. The method according to claim 1, characterized in that Annealing time is 0-24h.

7. The method according to claim 1, characterized in that The temperature of the two temperature zones during the film growth stage is 800-1200°C, and the time is 0-6h.

8. The method according to claim 1, characterized in that The introduced gas includes one or more of Ar, H2 and O2, including but not limited to a mixture of any two of them.

9. The method according to claim 1, characterized in that The gas flow rate is 0-2000 sccm.

10. A boron nitride thin film prepared by the preparation method according to any one of claims 1 to 9.

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