Method for preparing doped diamond

Abstract

A method for preparing doped diamond. The method comprises: placing a substrate and a target on a sample table of a reaction chamber in a microwave-plasma chemical vapor deposition system; cleaning the surfaces of the substrate and the target after the reaction chamber is vacuumized; inputting hydrogen into the reaction chamber and adjusting the cavity air pressure and microwave power of the reaction chamber, so as to implement the operations of glow discharge and heating in the reaction chamber; and with a methane gas and hydrogen as gas sources, irradiating the target with a laser to precipitate out laser-induced plasma, and doping a surface of the substrate with the laser-induced plasma, thereby growing doped diamond on the surface of the substrate. By means of a laser technique, a surface of the substrate is doped with the laser-induced plasma precipitated from the target so as to prepare doped diamond on the surface of the substrate, thereby improving the preparation efficiency of the doped diamond.

Description

A method for preparing doped diamond Technical Field

[0001] The present application relates to the field of optoelectronic technology, and in particular to a method for preparing doped diamond. Background Art

[0002] With the continuous development of the semiconductor industry, the performance of silicon-based semiconductor devices has gradually approached its theoretical limits. Diamond, as the ultimate semiconductor material, possesses excellent electrical properties such as a wide bandgap, high carrier mobility, high thermal conductivity, and a low dielectric constant. Due to these exceptional properties, the use of diamond in semiconductor power electronic devices has become a research hotspot. Pure diamond has poor conductivity and requires doping to form a pn junction. While p-type doping of diamond is currently well established, n-type doping still faces many challenges.

[0003] The doping methods for diamonds include in-situ doping and ion implantation. Among them, ion implantation is related to the lattice defects generated by radiation, which damages the lattice, and the doping concentration decreases with depth. The in-situ doping method is to directly introduce impurities during the process of growing diamonds by chemical vapor deposition (CVD) or high temperature and high pressure method (HPHT). However, the high temperature and high pressure method is difficult to prepare, the cost is high, and it is difficult to be applied on a large scale. At present, the CVD method mostly uses a gas source to dope diamonds. Impurities can be effectively and evenly incorporated into diamonds in the form of gas. However, this method has too harsh requirements on the gas source, and it is difficult to find a pure gas source of certain elements without impurity elements. Some studies have placed a solid source in a CVD reactor and used the temperature in the reactor to vaporize the solid source, so that impurity atoms penetrate into the diamond lattice during the vapor deposition process. However, this method has requirements for the melting and boiling points of the solid source itself, and it is difficult to control the doping amount, so it is not suitable for the doping of most elements. The laser and the material will instantly generate high temperatures (up to 10 5 K), high pressure (up to 10 GPa), high electron density (10 6 cm -3 ) plasma can introduce materials that are difficult to excite at normal temperatures into intrinsic materials. By changing the laser power and repetition frequency, the amount of impurity doping can be more accurately controlled. It is a doping method with great potential.

[0004] Therefore, in order to solve the technical problems of difficulty in diamond doping and poor doping quality in existing diamond doping methods, a method for preparing doped diamond is urgently needed.

[0005] Summary of the Invention

[0006] The purpose of this application is to provide a method for preparing doped diamonds. By using laser technology, laser-induced plasma precipitated from a target material is doped into the surface of a substrate, so that doped diamonds are prepared on the substrate surface. This method solves the problems of difficulty in diamond doping and poor doping quality in existing diamond doping methods. By using environmentally friendly gases such as methane and hydrogen for preparation, the conductive properties of diamonds are improved, and the preparation efficiency of doped diamonds is increased.

[0007] In a first aspect, the present application provides a method for preparing doped diamond, which is used to prepare doped diamond, comprising the steps of:

[0008] placing a substrate and a target material on a sample stage of a reaction chamber in a microwave plasma chemical vapor deposition system;

[0009] After the reaction chamber is vacuumed, the surface of the substrate and the surface of the target are cleaned;

[0010] Inputting hydrogen into the reaction chamber and adjusting the cavity gas pressure and microwave power of the reaction chamber to perform ignition operation and temperature increase operation in the reaction chamber;

[0011] Methane gas and hydrogen gas are used as gas sources, a laser is used to irradiate a target material to precipitate laser-induced plasma, and the laser-induced plasma is doped into the surface of the substrate to grow doped diamond on the surface of the substrate.

[0012] The doped diamond preparation method provided in the present application can realize the preparation of doped diamond. Through laser technology, the laser-induced plasma precipitated from the target material is doped into the surface of the substrate, so that doped diamond is prepared on the substrate surface. This solves the problems of difficulty in diamond doping and poor doping quality existing in existing diamond doping methods. The preparation is carried out using gases that do not pollute the environment, such as methane gas and hydrogen, which improves the conductive properties of diamond and increases the preparation efficiency of doped diamond.

[0013] Optionally, placing the substrate and the target on a sample stage of a reaction chamber in a microwave plasma chemical vapor deposition system includes:

[0014] placing the substrate in the center of the sample stage;

[0015] The target is placed at the edge area of ​​the sample stage.

[0016] The doped diamond preparation method provided in the present application can realize the preparation of doped diamonds by placing the substrate in the center of the sample stage and the target material in the edge area of ​​the sample stage. This placement method facilitates observation of the conditions of the substrate and the target material during the doped diamond preparation process, which is beneficial to improving the preparation efficiency of doped diamonds.

[0017] Optionally, after the reaction chamber is vacuumed, the surface of the substrate and the surface of the target are cleaned, including the following steps performed multiple times:

[0018] performing a vacuum operation on the reaction chamber;

[0019] A preset cleaning flow rate of hydrogen gas is introduced into the reaction chamber to clean the surface of the substrate and the surface of the target.

[0020] Optionally, the preset cleaning flow rate is 30 to 300 sccm; and the vacuuming operation is to reduce the vacuum degree of the reaction chamber to below 100 mTorr.

[0021] Optionally, inputting hydrogen into the reaction chamber and adjusting the cavity gas pressure and microwave power of the reaction chamber to perform ignition and temperature raising operations in the reaction chamber include:

[0022] Inputting hydrogen gas at a preset first flow threshold into the reaction chamber, adjusting the cavity pressure of the reaction chamber to the first pressure threshold and adjusting the microwave power of the reaction chamber to the first power threshold, so as to perform an ignition operation in the reaction chamber;

[0023] The input flow rate of the hydrogen gas is adjusted to a preset second flow rate threshold, the cavity gas pressure of the reaction chamber is adjusted to a second gas pressure threshold, the microwave power of the reaction chamber is adjusted to a second power threshold, and the target temperature of the reaction chamber is adjusted to a first temperature threshold, so as to perform a temperature increase operation in the reaction chamber.

[0024] The doped diamond preparation method provided in the present application can realize the preparation of doped diamond. By inputting hydrogen and adjusting the cavity gas pressure and microwave power of the reaction chamber, ignition operations and temperature increase operations are performed in the reaction chamber, which provides suitable preparation conditions for doped diamond and is conducive to improving the preparation efficiency of doped diamond.

[0025] Optionally, the first flow threshold is 20~120sccm, the first gas pressure threshold is 2~5Torr, the first power threshold is 1~2kW, the second flow threshold is 200~600sccm, the second gas pressure threshold is 50~120Torr, the second power threshold is 2~10kW, and the first temperature threshold is 750~900℃.

[0026] Optionally, using methane gas and the hydrogen gas as gas sources, irradiating a target material with a laser to precipitate laser-induced plasma, and allowing the laser-induced plasma to be doped into the surface of the substrate to grow doped diamond on the surface of the substrate, comprising:

[0027] Adjusting the focus of the laser beam to the target;

[0028] Maintaining the temperature elevation operation setting of the reaction chamber, while introducing methane gas at a preset third flow rate threshold, the laser is activated, so that the laser-induced plasma precipitated from the target material is doped into the surface of the substrate, thereby performing laser-induced doping on the substrate surface and growing doped diamond;

[0029] After a preset period, the target temperature of the reaction chamber is adjusted to room temperature, the introduction of the methane gas is stopped, and the flow rate of the hydrogen gas, the cavity pressure and the microwave power are gradually reduced. After the reaction chamber returns to room temperature, the doped diamond is prepared on the surface of the substrate.

[0030] Optionally, the power of the laser is 10 to 1000 W, the spot diameter of the laser is 10 to 600 μm, the pulse width of the laser is 1 fs to 500 ns, and the repetition frequency of the laser is 1 to 10 6 Hz.

[0031] Optionally, the preset third flow threshold is 2% to 6% of the preset second flow threshold.

[0032] Optionally, after maintaining the temperature rise operation setting of the reaction chamber, activating the laser while introducing methane gas at a preset third flow rate threshold, and allowing the laser-induced plasma precipitated from the target material to be doped into the surface of the substrate to perform laser-induced doping on the surface of the substrate and growth preparation of doped diamond, the method further includes:

[0033] The power and repetition frequency of the laser are adjusted to adjust the doping concentration of the impurities in the doped diamond.

[0034] Beneficial effects: The doped diamond preparation method provided in the present application uses laser technology to allow the laser-induced plasma precipitated from the target material to be doped into the surface of the substrate, so that doped diamond is prepared on the surface of the substrate, thereby solving the problems of difficulty in diamond doping and poor doping quality in existing diamond doping methods. The method uses methane gas and hydrogen gas, which are non-polluting gases to the environment, to improve the conductive properties of diamond and the preparation efficiency of doped diamond. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] FIG1 is a flow chart of a method for preparing doped diamond provided in an embodiment of the present application.

[0036] FIG2 is a schematic diagram of the laser-induced doping process of a substrate. DETAILED DESCRIPTION

[0037] The technical solutions in the embodiments of the present application will be clearly and completely described below in conjunction with the drawings in the embodiments of the present application. Obviously, the described embodiments are only a part of the embodiments of the present application, rather than all of the embodiments. The components of the embodiments of the present application generally described and shown in the drawings here can be arranged and designed in various different configurations. Therefore, the following detailed description of the embodiments of the present application provided in the drawings is not intended to limit the scope of the application for protection, but merely represents the selected embodiments of the present application. Based on the embodiments of the present application, all other embodiments obtained by those skilled in the art without making creative work fall within the scope of protection of the present application.

[0038] It should be noted that similar reference numerals and letters represent similar items in the following drawings. Therefore, once an item is defined in one drawing, it does not need to be further defined or explained in subsequent drawings. At the same time, in the description of this application, the terms "first", "second", etc. are only used to distinguish the description and should not be understood as indicating or implying relative importance.

[0039] Please refer to FIG1 , which shows a method for preparing doped diamond in some embodiments of the present application, which is used to prepare doped diamond, including:

[0040] Step S1, placing a substrate and a target material on a sample stage of a reaction chamber in a microwave plasma chemical vapor deposition system;

[0041] Step S2, after the reaction chamber is vacuumed, the surface of the substrate and the surface of the target are cleaned;

[0042] Step S3, inputting hydrogen into the reaction chamber and adjusting the cavity pressure and microwave power of the reaction chamber to perform ignition and temperature increase operations in the reaction chamber;

[0043] In step S4, methane gas and hydrogen gas are used as gas sources, and a laser is used to irradiate the target material to precipitate laser-induced plasma, and the laser-induced plasma is doped into the surface of the substrate to grow doped diamond on the surface of the substrate.

[0044] The doped diamond preparation method uses laser technology to dope laser-induced plasma precipitated from a target material into the surface of a substrate, thereby preparing doped diamond on the substrate surface. This method solves the problems of difficulty in diamond doping and poor doping quality in existing diamond doping methods. Environmentally friendly gases such as methane and hydrogen are used for preparation, thereby improving the conductive properties of diamond and increasing the preparation efficiency of doped diamond.

[0045] Specifically, in step S1, a substrate and a target are placed on a sample stage of a reaction chamber in a microwave plasma chemical vapor deposition system, including:

[0046] Place the substrate in the center of the sample stage;

[0047] Place the target on the edge of the sample stage.

[0048] In step S1, the substrate is placed in the center of the sample stage, and the target is placed at the edge of the sample stage. This placement allows direct observation of the substrate and target through the window of the microwave plasma chemical vapor deposition system, allowing the entire doped diamond production process to be observed. The substrate can be a heterogeneous or homogeneous substrate such as a silicon wafer, quartz wafer, molybdenum wafer, or diamond single crystal, and can be set according to actual needs. The target can be made of a metal, oxide, ceramic, or organic material, and can be in the form of a block, sheet, wire, or powder, and can be set according to actual needs.

[0049] Specifically, in step S2, after the reaction chamber is vacuumed, the surface of the substrate and the surface of the target are cleaned, including the following steps that are performed multiple times:

[0050] Performing a vacuum operation on the reaction chamber;

[0051] A preset cleaning flow rate of hydrogen gas is introduced into the reaction chamber to clean the surface of the substrate and the surface of the target.

[0052] In step S2, the following steps are performed multiple times: the vacuum level of the microwave plasma chemical vapor deposition system's reaction chamber is evacuated to below 100 mTorr, followed by the introduction of hydrogen gas at a flow rate of 30 to 300 sccm (preset purge flow rate). The hydrogen gas has a purity of no less than 7N. The evacuation and purge steps are repeated to ensure that the substrate, target, and reaction chamber are sufficiently clean.

[0053] Specifically, in step S3, hydrogen is input into the reaction chamber and the cavity pressure and microwave power of the reaction chamber are adjusted to perform ignition and temperature raising operations in the reaction chamber, including:

[0054] Inputting hydrogen gas at a preset first flow threshold into the reaction chamber, adjusting the cavity pressure of the reaction chamber to the first pressure threshold and adjusting the microwave power of the reaction chamber to the first power threshold, so as to perform an ignition operation in the reaction chamber;

[0055] The input flow rate of hydrogen is adjusted to a preset second flow threshold, the cavity gas pressure of the reaction chamber is adjusted to a second gas pressure threshold, the microwave power of the reaction chamber is adjusted to a second power threshold, and the target temperature of the reaction chamber is adjusted to a first temperature threshold to perform a temperature increase operation in the reaction chamber.

[0056] In step S3, 20 to 120 sccm (first flow threshold) of hydrogen is input into the reaction chamber, the cavity pressure of the reaction chamber is adjusted to 2 to 5 Torr (first pressure threshold), the microwave power of the reaction chamber is adjusted to 1 to 2 kW (first power threshold), and the microwave power is turned on to start the ignition operation.

[0057] 200 to 600 sccm (second flow threshold) of hydrogen is input into the reaction chamber, the cavity pressure of the reaction chamber is adjusted to 50 to 120 Torr (second pressure threshold), the microwave power of the reaction chamber is adjusted to 2 to 10 kW (second power threshold), and the target temperature of the reaction chamber is adjusted to 750 to 900°C (first temperature threshold) to perform a heating operation.

[0058] Specifically, in step S4, methane gas and hydrogen gas are used as gas sources, a laser is used to irradiate a target material to precipitate laser-induced plasma, and the laser-induced plasma is doped into the surface of a substrate to grow doped diamond on the surface of the substrate, including: adjusting the focus of the optical path of the laser to be on the target material;

[0059] Maintaining the temperature elevation operation settings of the reaction chamber (i.e., maintaining the temperature of the reaction chamber at a first temperature threshold, maintaining the input flow rate of hydrogen at a second flow rate threshold, maintaining the cavity pressure of the reaction chamber at a second flow pressure threshold, and maintaining the microwave power of the reaction chamber at a second power threshold), while introducing methane gas at a preset third flow rate threshold, activating the laser, so that the laser-induced plasma precipitated from the target material is doped into the surface of the substrate, thereby performing laser-induced doping on the substrate surface and growing doped diamond;

[0060] After a preset period, the target temperature of the reaction chamber is adjusted to room temperature, the introduction of methane gas is stopped, and the hydrogen flow, cavity pressure and microwave power are gradually reduced. After the reaction chamber returns to room temperature, doped diamonds are prepared on the surface of the substrate.

[0061] In step S4, the optical path of the laser is adjusted so that it passes through the window of the microwave plasma chemical vapor deposition system and the focus of the optical path of the laser is located on the target material. The power of the laser is 10 to 1000 W, the spot diameter of the laser is 10 to 600 μm, the pulse width of the laser is 1 fs to 500 ns, and the repetition frequency of the laser is 1 to 10 6 Hz.

[0062] The reaction chamber temperature is maintained at a first temperature threshold, the hydrogen input flow rate is maintained at a second flow rate threshold, the reaction chamber cavity pressure is maintained at a second flow pressure threshold, and the microwave power of the reaction chamber is maintained at a second power threshold. After the substrate surface temperature rises to 750-900°C, methane gas is introduced at a rate of 2%-6% (2%-6% of 200-600 sccm, i.e., a third flow rate threshold) of the hydrogen flow rate. The laser is simultaneously activated to perform laser-induced doping on the substrate surface and to prepare doped diamond growth. After the laser-induced doping, diamond doped with impurities, i.e., doped diamond, begins to grow on the substrate surface. The methane gas purity is no less than 6N. After being induced by the laser, the target material will precipitate laser-induced plasma, which will diffuse into the microwave-induced hydrogen-methane plasma. As a result, during the mixed plasma deposition process (a mixture of laser-induced plasma and hydrogen-methane plasma), the laser-induced plasma will be incorporated into the substrate surface, so that the location where the laser-induced plasma is incorporated into the substrate surface begins to grow diamond doped with impurity elements. The impurity elements are determined by the material of the target material. As shown in Figure 2, Figure 2 is a schematic diagram of the laser-induced doping process of the substrate. As can be seen from Figure 2, the laser-induced plasma precipitated from the target material diffuses into the microwave-induced plasma (microwave-induced hydrogen-methane plasma) to form a mixed plasma. During the mixed plasma deposition process, the laser-induced plasma will be incorporated into the substrate surface, so that the doped diamond will begin to grow at the corresponding location on the substrate surface.

[0063] After a preset period (e.g., 2 hours, but not limited thereto), the target temperature of the reaction chamber is adjusted to room temperature, the introduction of methane gas is stopped, and the hydrogen flow rate, cavity pressure, and microwave power are gradually reduced until the hydrogen flow rate, cavity pressure, and microwave power are zero. After the reaction chamber returns to room temperature, the substrate with doped diamond grown on its surface is removed to obtain diamond doped with impurity elements (doped diamond). The cooling rate is set to less than 1°C per second. This cooling rate can prevent thermal mismatch from causing large stress between the diamond and substrate surfaces, which may lead to damage to the diamond and substrate.

[0064] Specifically, after maintaining the temperature rise operation setting of the reaction chamber, and simultaneously starting the laser while introducing methane gas at a preset third flow rate threshold, so that the laser-induced plasma precipitated from the target material is doped into the surface of the substrate to perform laser-induced doping on the surface of the substrate and growth preparation of doped diamond, the method further includes:

[0065] The power and repetition rate of the laser are adjusted to adjust the doping concentration of the diamond.

[0066] After starting the laser to induce doping, the impurity doping concentration in the doped diamond is adjusted by adjusting the power and repetition frequency of the laser, so that high-quality doped diamond can be obtained.

[0067] As can be seen from the above, the method for preparing doped diamonds comprises placing a substrate and a target material on a sample stage of a reaction chamber in a microwave plasma chemical vapor deposition system, evacuating the reaction chamber, cleaning the surfaces of the substrate and the target material, inputting hydrogen into the reaction chamber, and adjusting the cavity pressure and microwave power of the reaction chamber to perform ignition and temperature raising operations in the reaction chamber, using methane gas and hydrogen as gas sources, irradiating the target material with a laser to precipitate laser-induced plasma, and causing the laser-induced plasma to be incorporated into the surface of the substrate, so that doped diamond grows on the surface of the substrate; thereby, through laser technology, the laser-induced plasma precipitated from the target material is incorporated into the surface of the substrate, so that doped diamond is prepared on the surface of the substrate, solving the problems of difficulty in diamond doping and poor doping quality in existing diamond doping methods, using methane gas and hydrogen gas that do not pollute the environment for preparation, improving the conductive properties of diamond, and increasing the preparation efficiency of doped diamond.

[0068] In this document, relational terms such as first and second, etc. are used merely to distinguish one entity or operation from another entity or operation, but do not necessarily require or imply any actual relationship or order between these entities or operations.

[0069] The above description is merely an embodiment of the present application and is not intended to limit the scope of protection of the present application. For those skilled in the art, various modifications and variations of the present application are possible. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present application shall be included in the scope of protection of the present application.

Claims

1. A method for preparing doped diamond, for preparing doped diamond, characterized in that: Includes steps: placing a substrate and a target material on a sample stage of a reaction chamber in a microwave plasma chemical vapor deposition system; After the reaction chamber is vacuumed, the surface of the substrate and the surface of the target are cleaned; Inputting hydrogen into the reaction chamber and adjusting the cavity gas pressure and microwave power of the reaction chamber to perform ignition operation and temperature increase operation in the reaction chamber; Methane gas and the hydrogen gas are used as gas sources, a laser is used to irradiate a target material to precipitate laser-induced plasma, and the laser-induced plasma is doped into the surface of the substrate to grow doped diamond on the surface of the substrate.

2. The method for preparing doped diamond according to claim 1, characterized in that: The substrate and target are placed on the sample stage of the reaction chamber of the microwave plasma chemical vapor deposition system, including: placing the substrate in the center of the sample stage; The target is placed at the edge area of ​​the sample stage.

3. The method for preparing doped diamond according to claim 1, characterized in that: After the reaction chamber is evacuated, the surface of the substrate and the surface of the target are cleaned, including the following steps performed multiple times: performing a vacuum operation on the reaction chamber; A preset cleaning flow rate of hydrogen gas is introduced into the reaction chamber to clean the surface of the substrate and the surface of the target.

4. The method for preparing doped diamond according to claim 3, characterized in that: The preset cleaning flow rate is 30-300 sccm; the vacuum pumping operation is to pump the vacuum degree of the reaction chamber to below 100 mTorr.

5. The method for preparing doped diamond according to claim 1, characterized in that: Inputting hydrogen into the reaction chamber and adjusting the cavity gas pressure and microwave power of the reaction chamber to perform ignition operation and temperature increase operation in the reaction chamber, including: Inputting hydrogen gas of a preset first flow threshold into the reaction chamber, adjusting the cavity pressure of the reaction chamber to the first pressure threshold and adjusting the microwave power of the reaction chamber to the first power threshold, so as to perform a ignition operation in the reaction chamber; The input flow rate of the hydrogen gas is adjusted to a preset second flow rate threshold, the cavity gas pressure of the reaction chamber is adjusted to a second gas pressure threshold, the microwave power of the reaction chamber is adjusted to a second power threshold, and the target temperature of the reaction chamber is adjusted to a first temperature threshold, so as to perform a temperature increase operation in the reaction chamber.

6. The method for preparing doped diamond according to claim 5, characterized in that: The first flow threshold is 20-120 sccm, the first gas pressure threshold is 2-5 Torr, the first power threshold is 1-2 kW, the second flow threshold is 200-600 sccm, the second gas pressure threshold is 50-120 Torr, the second power threshold is 2-10 kW, and the first temperature threshold is 750-900°C.

7. The method for preparing doped diamond according to claim 5, characterized in that: Using methane gas and the hydrogen gas as gas sources, irradiating a target material with a laser to precipitate laser-induced plasma, and allowing the laser-induced plasma to be doped into the surface of the substrate, so that doped diamond grows on the surface of the substrate, comprising: Adjusting the focus of the optical path of the laser to the target; The temperature-raising operation setting of the reaction chamber is maintained, and the laser is activated while a preset third flow threshold value of methane gas is introduced, so that the laser-induced plasma precipitated from the target material is doped into the surface of the substrate, so as to perform laser-induced doping on the surface of the substrate and growth preparation of doped diamond; After a preset period, the target temperature of the reaction chamber is adjusted to room temperature, the introduction of the methane gas is stopped, and the flow rate of the hydrogen gas, the cavity pressure and the microwave power are gradually reduced. After the reaction chamber returns to room temperature, the doped diamond is prepared on the surface of the substrate.

8. The method for preparing doped diamond according to claim 7, characterized in that: The power of the laser is 10 to 1000 W, the spot diameter of the laser is 10 to 600 μm, the pulse width of the laser is 1 fs to 500 ns, and the repetition frequency of the laser is 1 to 10 6 Hz.

9. The method for preparing doped diamond according to claim 7, characterized in that: The preset third flow rate threshold is 2% to 6% of the preset second flow rate threshold.

10. The method for preparing doped diamond according to claim 7, characterized in that: The temperature raising operation setting of the reaction chamber is maintained, and the laser is activated while the methane gas of a preset third flow rate threshold is introduced, so that the laser-induced plasma precipitated from the target material is doped into the surface of the substrate to perform laser-induced doping on the surface of the substrate and growth preparation of doped diamond, and further includes: The power and repetition frequency of the laser are adjusted to adjust the impurity doping concentration of the doped diamond.

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