Single crystal diamond polishing method based on high-voltage electrostatic field
By introducing a high-voltage electrostatic field and a specific catalytic chemical system into the polishing process of single-crystal diamond, the problem of low polishing efficiency of single-crystal diamond was solved, and a high-efficiency and low-damage polishing effect was achieved.
Patent Information
- Application Number
- CN202511886506.1
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-12-15
- Publication Date
- 2026-01-27
AI Technical Summary
Existing technologies struggle to polish single-crystal diamond efficiently and with minimal damage. Traditional methods, such as chemical mechanical polishing, are inefficient, while external field-assisted methods are complex or costly. Electrochemical mechanical polishing cannot be directly applied to insulators.
A high-voltage electrostatic field-assisted chemical mechanical polishing method is adopted. By introducing a high-voltage DC electric field into the polishing slurry and combining it with a specific catalytic chemical system, such as the Fe²⁺/H₂O₂Fenton system, the polishing efficiency is improved by utilizing field-induced electron emission and micro-area tip discharge.
It significantly improves the polishing removal rate of single-crystal diamond, achieving low-damage and high-efficiency surface finish, with polishing efficiency increased several times to 300 nm/h.
Smart Images
Figure CN121403218A_ABST
Abstract
Description
Technical Field
[0001] This invention belongs to the field of ultra-hard and brittle material processing technology, and in particular relates to a single-crystal diamond polishing method based on a high-voltage electrostatic field. Background Technology
[0002] Single-crystal diamond, as an ultra-hard, wide-bandgap semiconductor material, has broad application prospects in high-tech fields. However, its extremely high hardness and chemical inertness make it extremely difficult to achieve efficient, low-damage precision polishing. Traditional chemical mechanical polishing (CMP) technology relies on the synergy of mechanical grinding and slow chemical reactions such as the Fenton reaction, resulting in low material removal rates that are difficult to meet industrialization requirements.
[0003] To address this issue, existing technologies attempt to incorporate external field assistance. For example, electrochemical mechanical polishing (ECMP) is widely used for polishing conductive materials such as metals, but this requires the workpiece to be conductive to form a closed electrolytic circuit. ECMP technology cannot be directly applied to insulators such as single-crystal diamond. Furthermore, methods such as plasma-assisted and laser-assisted polishing suffer from problems such as complex equipment, high costs, or the potential for thermal damage.
[0004] Therefore, there is an urgent need in the field for a novel field-assisted polishing method that can be applied to insulating single-crystal diamond and effectively improve its polishing efficiency. Summary of the Invention
[0005] In view of this, the present invention aims to propose a single-crystal diamond polishing method based on a high-voltage electrostatic field to solve at least one technical problem in the prior art. The purpose of the present invention is to provide a method for improving the polishing removal rate of single-crystal diamond. The application of this method overcomes the problems in the prior art, such as poor polishing rate caused by the extremely high hardness and chemical inertness of diamond.
[0006] To achieve the above objectives, the technical solution of the present invention is implemented as follows: A method for polishing single-crystal diamond based on a high-voltage electrostatic field includes the following steps: during the polishing process, the single-crystal diamond is held in a clamp and polished using a polishing pad, and a strong electrostatic field sufficient to induce field-induced electron emission or tip discharge is established between the polishing pad and the single-crystal diamond. The strong electrostatic field is formed by applying a DC voltage; with the assistance of the strong electrostatic field, the single-crystal diamond is chemically and mechanically polished in a polishing slurry.
[0007] Furthermore, the high-voltage electrostatic field is established by connecting the polishing disc to the positive terminal of the high-voltage DC power supply and connecting the upper clamp of the clamp holding the single crystal diamond to the negative terminal of the high-voltage DC power supply.
[0008] Furthermore, the DC voltage is not less than 50V, preferably 80V to 1000V.
[0009] Furthermore, the polishing fluid includes polishing solvent, abrasive, catalyst, oxidant, dispersant, and pH adjuster.
[0010] Furthermore, the polishing solvent is water; The pH adjuster is H2SO4, and the mass fraction of the pH adjuster in the polishing solution is 0.01-10%.
[0011] Furthermore, the abrasive is diamond, the abrasive accounts for 10%-50% of the mass fraction of the polishing fluid, and the particle size of the abrasive is 0.01~100µm, preferably, the particle size of the abrasive is 0.01~10µm.
[0012] Furthermore, the catalyst is FeSO4, and the molar concentration of the catalyst in the polishing solution is 0.01-10 mol / L, preferably 0.01-5 mol / L.
[0013] Furthermore, the oxidant is H2O2, and the oxidant accounts for 0.01-20% of the mass fraction of the polishing solution, preferably 0.01-10%.
[0014] Furthermore, the dispersant is a nonionic surfactant, and the mass fraction of the dispersant in the polishing liquid is 0.01-10%, preferably 0.01-5%.
[0015] Furthermore, the load during polishing is 0.01~10 kg / cm². 2 The rotation speed is 0.1~1200 r / min, and the time is 0.25~10 h.
[0016] The core of this invention lies in the auxiliary effect of the high-voltage electrostatic field, which has broad compatibility and universality with the chemical system in the polishing slurry. The polishing slurry may contain, but is not limited to, oxidants such as peroxides (e.g., H₂O₂), permanganates, and perchlorates, as well as ionic or nanoparticle catalysts of metals such as iron, copper, titanium, and cobalt. Any method utilizing a high-voltage electrostatic field to assist in polishing single-crystal diamond falls within the protection scope of this invention.
[0017] The method is performed under open-circuit conditions. Although the polishing disc is connected to the positive terminal of the power supply and the upper fixture is connected to the negative terminal, a continuous conductive circuit is not formed due to the presence of an insulating medium (such as the diamond itself, the polishing pad, or air) between the single-crystal diamond body and its fixture system and the polishing disc. Under this configuration, the applied high voltage primarily establishes a high-voltage electrostatic field between the two electrodes. We hypothesize that this electrostatic field generates extremely high field strength at the microscopic protrusions on the diamond surface, which may induce field-induced electron emission, micro-area tip discharge, or the generation of trace plasmas. These physical effects transiently perturb and weaken the carbon-carbon bonds on the diamond surface, thereby significantly reducing the energy barrier for subsequent mechanical grinding and chemical reactions, resulting in a substantial improvement in the removal rate.
[0018] Compared with existing technologies, the single-crystal diamond polishing method based on a high-voltage electrostatic field described in this invention has the following advantages: This invention provides an electric field-assisted chemical mechanical polishing method. Compared to purely mechanical or high-energy beam polishing, which mainly relies on mechanical wear and impact, this removal mechanism, which primarily softens the workpiece surface, is more likely to achieve lower subsurface damage and better surface finish. This is a potential key quality advantage of this method.
[0019] This application revolutionizes the chemical mechanical polishing (CMP) removal rate of single-crystal diamond by introducing a high-voltage electrostatic field reaching a specific threshold strength in synergy with a specific catalytic chemical polishing slurry system. This not only significantly improves processing efficiency but also makes it possible to obtain high surface quality simultaneously due to the removal mechanism dominated by enhanced chemical reactions.
[0020] 3. This invention overcomes the problem of low polishing efficiency caused by the high chemical inertness of single-crystal diamond. The method is universally applicable to polishing slurry chemical systems and can achieve high-efficiency polishing in various catalytic systems. Experiments show that its polishing removal rate at room temperature can reach up to 300 nm / h, which is several times higher than that of traditional chemical mechanical polishing. Attached Figure Description
[0021] The accompanying drawings, which form part of this invention, are used to provide a further understanding of the invention. The illustrative embodiments of the invention and their descriptions are used to explain the invention and do not constitute an undue limitation of the invention. In the drawings: Figure 1 The following graphs show the removal rate results after polishing in Example 1 and Comparative Examples 1-6 of this invention. Detailed Implementation
[0022] It should be noted that, unless otherwise specified, the embodiments and features described in the present invention can be combined with each other.
[0023] The present invention will now be described in detail with reference to the accompanying drawings and embodiments.
[0024] Example 1 A 20% aqueous solution of 500 nm diamond was prepared by adding 2 mol / L FeSO4 and 1% nonionic surfactant (e.g., DM90) to an aqueous solution, followed by ultrasonic dispersion. Then, 1.2% H2O2 was added and stirred. Finally, the pH was adjusted to 2.5 with H2SO4. The polishing disc was connected to the positive terminal of a high-voltage DC power supply, and the upper clamp holding the single-crystal diamond was connected to the negative terminal. The power supply was set to 100V, and voltage was applied upon power-on. The diamond sheet was then polished using the prepared polishing solution with a DC voltage of 100V and a load of 3 kg / cm². 2 The electro-mechanical polishing process was performed at a rotation speed of 50 rpm, using a grooveless polyurethane polishing pad, for 50 min, with a polishing removal rate of 300 nm / h.
[0025] Comparative Example 1 1.2% H2O2 was added to a 20% aqueous solution of 500 nm diamond. No catalyst or dispersant was added. The solution was stirred, and the pH was adjusted to 2.5 with H2SO4. A diamond sheet was then loaded with a load of 3 kg / cm² using the prepared polishing solution. 2 Chemical mechanical polishing was performed at a speed of 50 rpm, using a grooveless polyurethane polishing pad, for 50 min, with a polishing removal rate of 40 nm / h.
[0026] Comparative Example 2 A 20% aqueous solution of 500 nm diamond was prepared by adding 2 mol / L FeSO4 and 1% nonionic surfactant (e.g., DM90) to an aqueous solution, followed by ultrasonic dispersion. Then, 1.2% H2O2 was added and the solution was stirred. Finally, the pH was adjusted to 2.5 with H2SO4. The diamond sheet was then subjected to a polishing solution with a loading of 3 kg / cm². 2 Chemical mechanical polishing was performed at a speed of 50 rpm, using a grooveless polyurethane polishing pad, for 50 minutes, with a polishing removal rate of 120 nm / h.
[0027] Comparative Example 3 1.2% H2O2 was added to a 20% aqueous solution of 500 nm diamond. No catalyst or dispersant was added. The solution was stirred, and the pH was adjusted to 2.5 with H2SO4. The polishing disc was connected to the positive terminal of a high-voltage DC power supply, and the upper clamp holding the single-crystal diamond was connected to the negative terminal. The power supply was set to 100 V, and voltage was applied upon power-on. The diamond sheet was then polished using the prepared polishing solution with a DC voltage of 100 V and a load of 3 kg / cm². 2The electro-mechanical polishing process was performed at a rotation speed of 50 rpm, using a grooveless polyurethane polishing pad, for 50 min, with a polishing removal rate of 80 nm / h.
[0028] Comparative Example 4 A diamond sheet was loaded with a load of 3 kg / cm using a 20% 500 nm diamond aqueous solution. 2 Mechanical polishing was performed at a speed of 50 rpm, using a grooveless polyurethane polishing pad, for 50 min, with a polishing removal rate of 20 nm / h.
[0029] Comparative Example 5 A 20% aqueous solution of 500 nm diamond was prepared by adding 2 mol / L FeSO4 and 1% nonionic surfactant (e.g., DM90) to an aqueous solution, followed by ultrasonic dispersion. Then, 1.2% H2O2 was added and stirred. Finally, the pH was adjusted to 2.5 with H2SO4. The polishing disc was connected to the positive terminal of a high-voltage DC power supply, and the upper clamp holding the single-crystal diamond was connected to the negative terminal. The power supply was set to 10V, and voltage was applied upon power-on. The diamond sheet was then polished using the prepared solution with a DC voltage of 10V and a load of 3 kg / cm². 2 The electro-mechanical polishing process was performed at a rotation speed of 50 rpm, using a grooveless polyurethane polishing pad, for 50 min, with a polishing removal rate of 70 nm / h.
[0030] Comparative Example 6 A 20% aqueous solution of 500 nm diamond was prepared, without oxidants or catalysts. The polishing disc was connected to the positive terminal of a high-voltage DC power supply, and the upper clamp holding the single-crystal diamond was connected to the negative terminal. The power supply was set to 100 V, and voltage was applied upon power-on. The diamond sheet was then polished using the prepared solution at a DC voltage of 100 V and a load of 3 kg / cm². 2 The electro-mechanical polishing process was performed at a rotation speed of 50 rpm, using a grooveless polyurethane polishing pad, for 50 min, with a polishing removal rate of 57 nm / h.
[0031] Comparative Example 1 only added an oxidant, and the removal rate was far lower than that of Example 1. This application creatively discovers that combining a high-voltage electrostatic field with a specific Fenton catalytic chemical system can produce a synergistic effect.
[0032] Compared to basic chemical mechanical polishing, the removal rate of Example 1 was 2.5 times that of Comparative Example 2. This indicates that the introduction of the high-voltage electrostatic field is not simply additive, but rather has a strong activating or enhancing effect on the chemical polishing process, significantly improving the efficiency of the chemical reaction.
[0033] The removal rate of Example 1 is much higher than that of Comparative Example 3. A high-voltage electrostatic field cannot generate an extremely high removal rate on its own; it must work in synergy with a specific catalytic chemical system (Fe²⁺ / H₂O₂ Fenton or Fenton-like system) to achieve the best results. This application has discovered a highly efficient synergistic pathway between these two systems.
[0034] The removal rate of Example 1 was significantly higher than that of Comparative Example 4. This demonstrates the tremendous synergistic effect of combining a high-voltage electrostatic field with chemical mechanical polishing, which far exceeds the effect of simple mechanical wear.
[0035] Comparative Example 5 showed a removal rate of only 70 nm / h, even lower than Comparative Example 2, which did not use an electric field. The beneficial effects described in this method require the electric field strength to reach a critical threshold. Too low an electric field is not only unhelpful but may also interfere with the chemical process. This underscores the validated and necessary nature of the high-voltage range (80V-1000V) defined in this application.
[0036] The applicant declares that the detailed structural features of the present invention are illustrated through the above embodiments, but the present invention is not limited to the above detailed structural features, that is, it does not mean that the present invention must rely on the above detailed structural features to be implemented. Those skilled in the art should understand that any improvements to the present invention, equivalent substitutions for the components selected in the present invention, additions of auxiliary components, selection of specific methods, etc., all fall within the protection scope and disclosure scope of the present invention.
Claims
1. A method for polishing single-crystal diamond based on a high-voltage electrostatic field, characterized in that: The process includes the following steps: during the polishing of single-crystal diamond, the single-crystal diamond is held in a clamp and polished using a polishing disc. A high-voltage electrostatic field is applied between the polishing disc and the single-crystal diamond, which is formed by applying a DC voltage. With the assistance of the high-voltage electrostatic field, the single-crystal diamond is chemically and mechanically polished in a polishing slurry.
2. The single-crystal diamond polishing method based on a high-voltage electrostatic field according to claim 1, characterized in that: The high-voltage electrostatic field is established by connecting the polishing disc to the positive terminal of the high-voltage DC power supply and connecting the upper clamp of the clamp holding the single crystal diamond to the negative terminal of the high-voltage DC power supply.
3. The single-crystal diamond polishing method based on a high-voltage electrostatic field according to claim 1, characterized in that: The DC voltage is not less than 50V, preferably 80V to 1000V.
4. The single-crystal diamond polishing method based on a high-voltage electrostatic field according to claim 1, characterized in that: Polishing fluids include polishing solvents, abrasives, catalysts, oxidants, dispersants, and pH adjusters.
5. The single-crystal diamond polishing method based on a high-voltage electrostatic field according to claim 4, characterized in that: The polishing solvent is water; The pH adjuster is H2SO4, and the mass fraction of the pH adjuster in the polishing solution is 0.01-10%.
6. The single-crystal diamond polishing method based on a high-voltage electrostatic field according to claim 4, characterized in that: The abrasive is diamond, and the abrasive accounts for 10%-50% of the mass fraction of the polishing fluid. The particle size of the abrasive is 0.01~100µm, preferably 0.01~10µm.
7. The single-crystal diamond polishing method based on a high-voltage electrostatic field according to claim 4, characterized in that: The catalyst is FeSO4, and the molar concentration of the catalyst in the polishing solution is 0.01-10 mol / L, preferably 0.01-5 mol / L.
8. The single-crystal diamond polishing method based on a high-voltage electrostatic field according to claim 4, characterized in that: The oxidant is H2O2, and the oxidant accounts for 0.01-20% of the mass fraction of the polishing solution, preferably 0.01-10%.
9. The single-crystal diamond polishing method based on a high-voltage electrostatic field according to claim 4, characterized in that: The dispersant is a nonionic surfactant, and the mass fraction of the dispersant in the polishing liquid is 0.01-10%, preferably 0.01-5%.
10. The single-crystal diamond polishing method based on a high-voltage electrostatic field according to claim 1, characterized in that: The load during polishing is 0.01~10 kg / cm. 2 The rotation speed is 0.1~1200 r / min, and the time is 0.25~10 h.