阅读说明：本技术 一种多晶金刚石膜的抛光方法 (Polishing method of polycrystalline diamond film ) 是由 冯曙光 于金凤 李光存 于 2021-09-17 设计创作，主要内容包括：本发明属于金刚石加工技术领域,具体公开了一种多晶金刚石膜的抛光方法,包括以下步骤：S1.清洗金刚石膜,然后干燥；S2.将铁、钴、镍、铜及其氧化物或氢氧化物中的一种或多种混合物配置成凝胶溶液或浆料,均匀旋涂在金刚石膜表面,得旋涂后的金刚石膜；S3.低温烘干金刚石膜；S4.将低温烘干后的金刚石膜进行刻蚀,得刻蚀后的金刚石膜；S5.将金刚石膜进行酸洗,酸洗完成后使用丙酮、无水乙醇、去离子水清洗；S6.将金刚石膜进行化学机械抛光；S7.清洗金刚石膜。本发明方法可有效避免多晶金刚石表面的损伤及破裂,提高抛光质量,节约成本。(The invention belongs to the technical field of diamond processing, and particularly discloses a polishing method of a polycrystalline diamond film, which comprises the following steps: s1, cleaning a diamond film, and then drying; s2, preparing one or more of mixture of iron, cobalt, nickel, copper and oxide or hydroxide thereof into gel solution or slurry, and uniformly spin-coating the gel solution or slurry on the surface of the diamond film to obtain the spin-coated diamond film; s3, drying the diamond film at a low temperature; s4, etching the diamond film dried at the low temperature to obtain the etched diamond film; s5, acid washing is carried out on the diamond film, and after the acid washing is finished, acetone, absolute ethyl alcohol and deionized water are used for cleaning; s6, chemically and mechanically polishing the diamond film; and S7, cleaning the diamond film. The method can effectively avoid the damage and the rupture of the surface of the polycrystalline diamond, improve the polishing quality and save the cost.)

1. A polishing method of a polycrystalline diamond film, characterized by comprising the steps of:

s1, cleaning a diamond film, and then drying;

s2, preparing one or more of mixture of iron, cobalt, nickel, copper and oxide or hydroxide thereof into gel solution or slurry, and uniformly spin-coating the surface of the diamond film obtained in the step S1 to obtain the spin-coated diamond film;

s3, drying the diamond film spin-coated in the step S2 at a low temperature;

s4, etching the diamond film dried at the low temperature in the step S3 to obtain the etched diamond film;

s5, carrying out acid washing on the diamond film etched in the step S4, and cleaning the diamond film by using acetone, absolute ethyl alcohol and deionized water after the acid washing is finished;

s6, chemically and mechanically polishing the diamond film cleaned in the step S5;

s7, cleaning the diamond film chemically and mechanically polished in the step S6.

2. The method for polishing a polycrystalline diamond film according to claim 1, wherein the size of the iron, cobalt, nickel, copper, and oxides or hydroxides thereof is in the nanometer range in step S2, and preferably the gel solution is prepared by a gel method using iron, cobalt, nickel, copper, and oxides or hydroxides thereof.

3. The method of polishing a polycrystalline diamond film according to claim 1, wherein in step S2, the spin coating thickness is 1 to 50 μm; the preferable specific parameters of the spin coating process are as follows: 100-10000 r/min, and 10-60 s of spin coating time.

4. The method for polishing a polycrystalline diamond film according to claim 1, wherein in step S3, the low-temperature baking process comprises: and (4) performing drying treatment at 40-60 ℃ for 40-80 min.

5. The method for polishing a polycrystalline diamond film according to claim 1, wherein in step S4, the etching process comprises sequentially subjecting the diamond film dried at a low temperature in step S3 to oxygen etching, plasma and metal active catalytic etching, and plasma etching;

preferably, the step S4 specifically includes:

s41, oxygen etching: the atmosphere is at least one of oxygen, argon and air, the pressure is 5-10 KPa, the temperature is 200-500 ℃, and the time is 5-10 min;

s42, plasma and metal active catalytic etching: the atmosphere is at least one of hydrogen, carbon monoxide, argon and helium, the pressure is 8-15 KPa, the temperature is 500-900 ℃, and the time is 10-120 min;

s43, plasma etching: the atmosphere is at least one of oxygen, argon, nitrogen, air and carbon monoxide, the pressure is 5-10 KPa, the temperature is 200-500 ℃, and the time is 5-40 min.

6. The method of polishing a polycrystalline diamond film according to claim 1, wherein in the step S6, in the chemical mechanical polishing process: an elastic polishing pad is adopted, diamond particles are used as abrasive materials, and polishing solution is strong oxidizing solution.

7. The method for polishing a polycrystalline diamond film according to claim 6, wherein the polishing pad is made of polyurethane, the polishing solution is a hydrogen peroxide solution or a potassium permanganate solution, and the abrasive is diamond particles having a particle size of 0.5 to 10 μm.

8. The method for polishing a polycrystalline diamond film according to claim 6 or 7, wherein step S6 is specifically:

s61, fixing the diamond film cleaned in the step S5 on a carrying disc, setting the rotating speed of the carrying disc to be 10-20 r/min, fixing a polishing pad on a polishing disc, setting the rotating speed of the polishing disc to be 40-100 r/min, polishing diamond particles with the abrasive material of 5-10 microns for 0.5-3 h, and cleaning;

s62, fixing the diamond film polished and cleaned in the step S61 on a carrying disc, setting the rotating speed of the carrying disc to be 10-50 r/min, fixing a polishing pad on a polishing disc, setting the rotating speed of the polishing disc to be 20-150 r/min, and polishing for 0.5-2 h, wherein the abrasive is a mixed abrasive of diamond particles with the particle size of 0.5 mu m or 2 mu m.

9. The method for polishing a polycrystalline diamond film according to claim 1, wherein the acid washing in step S5 is specifically: and (5) putting the diamond film etched in the step (S4) into aqua regia solution, and cleaning for 3-10 min.

10. The method for polishing a polycrystalline diamond film according to claim 1 or 9, wherein the cleaning processes of steps S1, S5, S7 are specifically: and ultrasonically cleaning the glass substrate for 5-10 min by using acetone, absolute ethyl alcohol and deionized water in sequence.

Technical Field

The invention belongs to the technical field of diamond processing, particularly relates to a polishing method of a diamond film, and more particularly relates to a method for quickly polishing a polycrystalline diamond film.

Background

Diamond has various excellent properties and is always concerned by scholars at home and abroad. With the gradual maturity of the artificial diamond preparation technology, diamonds are widely applied in the fields of abrasive tools and the like, but the high and new technical fields of military, aerospace, micro-nano sensors and the like have extremely high requirements on the surface quality of diamonds, such as the requirement of optical-grade diamond films on large enough area, low enough roughness and the like, and the physical and chemical characteristics of high hardness, high brittleness, high chemical inertness and the like of the diamonds cause that the conventional material processing and forming technology has very limited effect on the diamond films, thereby limiting the application of the diamonds in the high and new technical fields.

In order to meet the high surface quality requirement of diamond films in the high and new technical fields, domestic and foreign scholars propose various processing methods of diamond crystals, such as mechanical polishing, thermochemical polishing, laser polishing, plasma beam polishing, chemical mechanical polishing and the like. However, the traditional mechanical polishing is easy to cause surface damage of the diamond film, the thermochemical polishing is easy to cause surface pollution of the diamond, the laser polishing can only be used for rough polishing of the surface of the diamond film generally, the equipment is expensive, the plasma beam polishing can only polish small-size diamond samples, the equipment is expensive, and the chemical mechanical polishing can obtain high surface quality at lower production cost, thereby drawing great attention. However, before chemical mechanical polishing, mechanical grinding and polishing, i.e. rough polishing, are generally required to reduce the abrasion loss of chemical mechanical polishing and improve the working efficiency, and the abrasive used in rough grinding has large particles and is easy to cause diamond surface damage and even micro-fracture; particularly, the polycrystalline diamond film has a certain bow shape on the diamond plane due to the difference of the thermal conductivity and the thermal expansion coefficient between the diamond and a foreign substrate, when the chemical mechanical polishing is carried out, the diamond film is likely to crack due to overlarge pressure, and a part of unpolished area exists on the diamond film plane due to the overlarge pressure.

Disclosure of Invention

Aiming at the problems in the prior art, the invention aims to provide a polishing method of a polycrystalline diamond film, which can effectively avoid the damage and the fracture of the surface of the polycrystalline diamond film, improve the polishing quality and save the cost.

In order to realize the purpose of the invention, the specific technical scheme is as follows:

a polishing method of a polycrystalline diamond film, comprising the steps of:

s1, cleaning a diamond film, and then drying;

s2, preparing one or more of mixture of iron, cobalt, nickel, copper and oxide or hydroxide thereof into gel solution or slurry, and uniformly spin-coating the surface of the diamond film obtained in the step S1 to obtain the spin-coated diamond film;

s3, drying the diamond film spin-coated in the step S2 at a low temperature;

s4, etching the diamond film dried at the low temperature in the step S3 to obtain the etched diamond film;

s5, carrying out acid washing on the diamond film etched in the step S4, and cleaning the diamond film by using acetone, absolute ethyl alcohol and deionized water after the acid washing is finished;

s6, chemically and mechanically polishing the diamond film cleaned in the step S5;

s7, cleaning the diamond film chemically and mechanically polished in the step S6.

Further, in step S2, the size of the iron, cobalt, nickel, copper and their oxides or hydroxides is in the nanometer level, and it is further preferable that the gel solution is a gel of iron, cobalt, nickel, copper and their oxides or hydroxidesMethod ofAnd (4) preparation.

Further, in step S2, spin coating to a thickness of 1-50 μm; the preferable specific parameters of the spin coating process are as follows: 100-10000 r/min, and 10-60 s of spin coating time.

Further, in step S3, the low-temperature drying process includes: and (4) performing drying treatment at 40-60 ℃ for 40-80 min.

Further, in step S4, the etching process includes sequentially performing oxygen etching, plasma and metal active catalytic etching, and plasma etching on the diamond film dried at the low temperature in step S3;

more preferably, step S4 specifically includes:

s41, oxygen etching: the atmosphere is at least one of oxygen, argon and air, the pressure is 5-10 KPa, the temperature is 200-500 ℃, and the time is 5-10 min;

s42, plasma and metal active catalytic etching: the atmosphere is at least one of hydrogen, carbon monoxide, argon and helium, the pressure is 8 to 15KPa, the temperature is 500 to 900 ℃, the time is 10 to 120min,

s43, plasma etching: the atmosphere is at least one of oxygen, argon, nitrogen, air and carbon monoxide, the pressure is 5-10 KPa, the temperature is 200-500 ℃, and the time is 5-40 min.

The significance of the plasma etching setting the three stages of oxygen etching, plasma and metal active catalytic etching and plasma etching is as follows: the purpose of the oxygen etching is to remove the gel and expose the metal or oxide or hydroxide; the plasma and metal active catalytic etching aims at converting diamond into graphite and continuously removing the graphite; the purpose of plasma etching is to oxidize the metal or carbide to metal oxide for subsequent acid cleaning removal, and also to oxidize and remove the graphite which is not removed.

Further, in step S6, during the chemical mechanical polishing process: an elastic polishing pad is adopted, diamond particles are used as abrasive materials, and polishing solution is strong oxidizing solution.

Further, the polishing pad is made of polyurethane, the polishing solution is hydrogen peroxide solution or potassium permanganate solution, and the abrasive is 0.5-10 μm diamond particles.

Further preferably, step S6 specifically includes:

s61, fixing the diamond film cleaned in the step S5 on a carrying disc, setting the rotating speed of the carrying disc to be 10-20 r/min, fixing a polishing pad on a polishing disc, setting the rotating speed of the polishing disc to be 40-100 r/min, polishing diamond particles with the abrasive material of 5-10 microns for 0.5-3 h, and cleaning;

s62, fixing the diamond film polished and cleaned in the step S61 on a carrying disc, setting the rotating speed of the carrying disc to be 10-50 r/min, fixing a polishing pad on a polishing disc, setting the rotating speed of the polishing disc to be 20-150 r/min, and polishing for 0.5-2 h, wherein the abrasive is a mixed abrasive of diamond particles with the particle size of 0.5 mu m or 2 mu m.

Further, in step S5, the acid washing specifically includes: and (5) putting the diamond film etched in the step (S4) into aqua regia solution, and cleaning for 3-10 min.

Further, the cleaning processes in steps S1, S5, and S7 are specifically: and ultrasonically cleaning the glass substrate for 5-10 min by using acetone, absolute ethyl alcohol and deionized water in sequence.

Compared with the prior art, the invention has the beneficial effects that:

(1) the polishing method of the diamond film creatively combines gel spin coating, plasma metal active catalytic etching and a chemical mechanical polishing method, replaces rough polishing treatment with non-contact etching, can effectively avoid the damage and micro-fracture of the surface of the diamond film caused by mechanical contact, improves the surface quality of the polished diamond film, and is particularly suitable for the surface polishing of large-area diamond films.

(2) Compared with mechanical grinding, the diamond film polishing method has the advantages that the redundant diamond can be quickly and continuously removed by plasma metal active catalytic etching in a shorter time, the polishing speed is greatly improved, particularly, the metal active catalytic etching is based on the carbon dissolving effect of transition metal elements on the diamond, the diamond is quickly etched, the surface of the etched diamond film is fluffy and porous, the subsequent chemical mechanical polishing is facilitated, and the polishing efficiency is improved.

(3) The polishing method of the diamond film adopts the polishing pad with certain elasticity instead of the polishing sheet of alumina and the like with extremely high hardness when in chemical mechanical polishing, the size of the abrasive material is not single but is formed by mixing the abrasive materials with different sizes, and the cracking of the diamond surface due to bow can be effectively avoided.

(4) The polishing method of the diamond film has lower cost of used equipment and is suitable for industrial popularization.

Drawings

FIG. 1 is a process flow diagram of an embodiment of the present invention.

Detailed Description

In order to facilitate an understanding of the invention, the invention will be described more fully and in detail below with reference to the accompanying drawings and preferred embodiments, but the scope of the invention is not limited to the specific embodiments below.

Unless otherwise defined, all terms of art used hereinafter have the same meaning as commonly understood by one of ordinary skill in the art. The terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the scope of the present invention.

Unless otherwise specifically stated, various raw materials, reagents, instruments, equipment and the like used in the present invention are commercially available or can be prepared by existing methods.

Example 1

The embodiment provides a polishing method of a polycrystalline diamond film, which comprises the following steps:

s1, ultrasonically cleaning a polycrystalline diamond film for 5min by using acetone, absolute ethyl alcohol and deionized water in sequence;

s2, measuring 20mL of FeCl₃(0.5 mol/L) solution is placed in a beaker, 20mL of NaOH (1.5 mol/L) solution is measured, FeCl is dripped into the solution₃2mL of Anionic Polyacrylamide (APAM), stirring, after completion of the dropwise addition, standing for aging to form Fe (OH)₃Colloid, Fe (OH) obtained₃The average size of the colloid particles is less than 200nm, the colloid particles are uniformly spin-coated on the surface of the diamond film, the process parameters in the spin-coating process are set to be 8000r/min, the spin-coating time is 50s, and the thickness is 10 mu m;

s3, putting the diamond film spin-coated in the step S2 into an oven at 40 ℃, and keeping the temperature for 50 min;

s4, putting the diamond film dried at the low temperature in the step S3 into plasma equipment to sequentially perform oxygen etching, plasma and metal active catalytic etching and plasma etching; the method specifically comprises the following steps:

s41, oxygen etching: the atmosphere is oxygen and argon, the volume ratio of the oxygen to the argon is 1:3, the pressure is 5kPa, the temperature is 500 ℃, and the time is 5 min;

s42, plasma and metal active catalytic etching: the atmosphere is hydrogen and argon, the volume ratio of the hydrogen to the argon is 8:1, the pressure is 15KPa, the temperature is 900 ℃, and the time is 10 min;

s43, plasma etching: the atmosphere is argon and oxygen, the volume ratio of the argon to the oxygen is 1:3, the pressure is 10KPa, the temperature is 500 ℃, and the time is 5 min;

obtaining an etched diamond film;

s5, putting the diamond film etched in the step S4 into aqua regia solution, cleaning for 3min at 40 ℃, and after acid cleaning, sequentially ultrasonically cleaning for 10min by using acetone, absolute ethyl alcohol and deionized water;

s6, chemically and mechanically polishing the diamond film cleaned in the step S5, specifically:

s61, fixing the cleaned diamond on a carrying disc at a rotating speed of 10r/min, fixing a polyurethane elastic polishing pad on the polishing disc at a rotating speed of 40r/min, polishing the diamond particles with abrasive materials of 10 microns by using hydrogen peroxide solution for 0.5h, and then performing ultrasonic cleaning;

s62, fixing the cleaned diamond on a carrying disc at a rotating speed of 10r/min, fixing a polyurethane elastic polishing pad on the polishing disc at a rotating speed of 100r/min, wherein the abrasive is a mixed abrasive of diamond particles of 0.5 mu m and 2 mu m, and the polishing solution is a hydrogen peroxide strong oxidizing solution and polishes for 0.5 h;

obtaining a polished diamond film;

and S7, ultrasonically cleaning the diamond film chemically and mechanically polished in the step S6 for 5min by using acetone, absolute ethyl alcohol and deionized water in sequence.

Example 2

This embodiment is basically the same as embodiment 1, except that:

s2, measuring 20mL of FeCl₃(0.5 mol/L) solution is placed in a beaker, 20mL of NaOH (1.5 mol/L) solution is measured, FeCl is dripped into the solution₃2mL of Anionic Polyacrylamide (APAM), stirring, after completion of the dropwise addition, standing for aging to form Fe (OH)₃Colloid, Fe (OH) obtained₃The average size of the colloid particles is less than 200nm, the colloid particles are uniformly spin-coated on the surface of the diamond film, the process parameters in the spin-coating process are set to be 8000r/min, the spin-coating time is 50s, and the thickness is 20 mu m;

s4, putting the diamond film dried at the low temperature in the step S3 into plasma equipment to sequentially perform oxygen etching, plasma and metal active catalytic etching and plasma etching; the method specifically comprises the following steps:

s41, oxygen etching: the atmosphere is air, the pressure is 5kPa, the temperature is 500 ℃, and the time is 5 min;

s42, plasma and metal active catalytic etching: the atmosphere is hydrogen and argon, the volume ratio of the hydrogen to the argon is 8:1, the pressure is 8KPa, the temperature is 500 ℃, and the time is 120 min;

s43, plasma etching: the atmosphere is argon and oxygen, the volume ratio of the argon to the oxygen is 1:6, the pressure is 10KPa, the temperature is 500 ℃, and the time is 8 min;

and obtaining the etched diamond film.

Example 3

This embodiment is basically the same as embodiment 1, except that:

s2, measuring 5g of ferric hydroxide, placing the ferric hydroxide in a mortar, measuring 30m l terpineol, dripping the terpineol into the mortar, continuously stirring for 10min to obtain Fe (OH)₃The average size of the slurry particles is less than 200nm, the slurry particles are uniformly spin-coated on the surface of the diamond film, the process parameters in the spin-coating process are set to be 8000r/min, the spin-coating time is 50s, and the thickness is 30 mu m;

s4, putting the diamond film dried at the low temperature in the step S3 into plasma equipment to sequentially perform oxygen etching, plasma and metal active catalytic etching and plasma etching; the method specifically comprises the following steps:

s41, oxygen etching: the atmosphere is air, the pressure is 5kPa, the temperature is 500 ℃, and the time is 5 min;

s42, plasma and metal active catalytic etching: the atmosphere is hydrogen and argon, the volume ratio of the hydrogen to the argon is 8:1, the pressure is 15KPa, the temperature is 900 ℃, and the time is 10 min;

s43, plasma etching: the atmosphere is argon and oxygen, the volume ratio of the argon to the oxygen is 1:3, the pressure is 10KPa, the temperature is 500 ℃, and the time is 11 min;

obtaining an etched diamond film;

s6, chemically and mechanically polishing the diamond film cleaned in the step S5, specifically:

s61, fixing the cleaned diamond on a carrying disc at a rotating speed of 10r/min, fixing a polyurethane elastic polishing pad on the polishing disc at a rotating speed of 40r/min, polishing the diamond particles with the abrasive material of 8 microns by using hydrogen peroxide solution for 2 hours, and then performing ultrasonic cleaning;

s62, fixing the cleaned diamond on a carrying disc at a rotating speed of 10r/min, fixing a polyurethane elastic polishing pad on the polishing disc at a rotating speed of 100r/min, wherein the abrasive is a mixed abrasive of diamond particles of 0.5 microns and 2 microns, and the polishing solution is a hydrogen peroxide strong oxidizing solution and is polished for 1 h;

and obtaining the polished diamond film.

Comparative example 1

This comparative example is substantially the same as example 1, except that:

s4, putting the diamond film dried at the low temperature in the step S3 into plasma equipment to sequentially perform oxygen etching, plasma and metal active catalytic etching and plasma etching; the method specifically comprises the following steps:

s41, oxygen etching: the atmosphere is air, the pressure is 5kPa, the temperature is 500 ℃, and the time is 5 min;

s42, plasma and metal active catalytic etching: argon gas is used as atmosphere, the pressure is 8KPa, the temperature is 400 ℃, and the time is 120 min;

s43, plasma etching: argon gas is used as atmosphere, the pressure is 10KPa, the temperature is 500 ℃, and the time is 5 min;

obtaining an etched diamond film;

comparative example 2

This comparative example is substantially the same as example 1, except that:

s2, measuring 20mL of FeCl₃(0.5 mol/L) solution is placed in a beaker, 20mL of NaOH (1.5 mol/L) solution is measured, FeCl is dripped into the solution₃2mL of Anionic Polyacrylamide (APAM), stirring, after completion of the dropwise addition, standing for aging to form Fe (OH)₃Colloid, Fe (OH) obtained₃The average size of the colloid is less than 200nm, the colloid is uniformly coated on the surface of the diamond film in a spinning way, the process parameter is set to be 8000r/min in the spinning process, the spinning time is 50s, and the thickness is 20 mu m.

S4, putting the diamond film dried at the low temperature in the step S3 into plasma equipment to sequentially perform oxygen etching, plasma and metal active catalytic etching and plasma etching; the method specifically comprises the following steps:

s41, oxygen etching: the atmosphere is air, the pressure is 5kPa, the temperature is 500 ℃, and the time is 5 min;

s42, plasma and metal active catalytic etching: argon gas is used as atmosphere, the pressure is 15KPa, the temperature is 900 ℃, and the time is 10 min;

s43, plasma etching: argon gas is used as atmosphere, the pressure is 10KPa, the temperature is 500 ℃, and the time is 8 min;

obtaining an etched diamond film;

s6, chemically and mechanically polishing the diamond film cleaned in the step S5, specifically:

s61, fixing the cleaned diamond on a carrying disc at a rotating speed of 10r/min, fixing a polyurethane elastic polishing pad on the polishing disc at a rotating speed of 40r/min, polishing the diamond particles with 30 mu m of abrasive materials by using hydrogen peroxide solution as polishing liquid, and polishing for 2 hours, and then carrying out ultrasonic cleaning;

s62, fixing the cleaned diamond on a carrying disc at a rotating speed of 10r/min, fixing a polyurethane elastic polishing pad on the polishing disc at a rotating speed of 100r/min, wherein the abrasive is a 20-micron diamond particle abrasive, and the polishing solution is a hydrogen peroxide strong oxidizing solution and polishes for 1 h;

and obtaining the polished diamond film.

Comparative example 3

An embodiment provides a polishing method of a polycrystalline diamond film, including the steps of:

y1. fixing the diamond on the sample carrying disc of the polishing machine, starting the polishing machine, rotating the sample carrying disc at 15r/min and the grinding disc at 80r/min, continuously adding a mixture of olive oil and 10 μm diamond micropowder to the grinding disc, and grinding for 2 h.

Y2. ultrasonic cleaning the diamond ground in the step Y1 with acetone, absolute ethyl alcohol and deionized water for 10 min;

y3., performing chemical mechanical polishing on the diamond film cleaned in the step Y2, specifically:

y31, fixing the cleaned diamond on a carrier disc at a rotating speed of 10r/min, fixing a polyurethane elastic polishing pad on the polishing disc at a rotating speed of 40r/min, polishing the diamond particles with abrasive materials of 10 microns by using hydrogen peroxide solution for 2 hours, and then performing ultrasonic cleaning;

fixing the cleaned diamond on a carrier disc at a rotating speed of 10r/min, fixing a polyurethane elastic polishing pad on the polishing disc at a rotating speed of 100r/min, wherein the abrasive is a mixed abrasive of diamond particles of 0.5 microns and 2 microns, and the polishing solution is a hydrogen peroxide strong oxidizing solution, and polishing for 1 h;

obtaining a polished diamond film;

y4., ultrasonically cleaning the diamond film chemically and mechanically polished in the step Y3 for 10min by acetone, absolute ethyl alcohol and deionized water in sequence.

Test of

The unpolished polycrystalline diamond film used in this example and the polished diamond films obtained in example 1/2/3 and comparative example 1/2/3 were subjected to the test, and the data obtained are shown in Table 1.

TABLE 1