Preparation method of MPCVD diamond film with high NV color center strength

Abstract

A method for preparing a diamond film with high NV color center strength through MPCVD is characterized in that a nitrogen-doped micron diamond film is deposited on a substrate through MPCVD, a reactive ion etching technology is used for conducting surface modification on the diamond film, structural conditions are improved for the high NV color center strength, vacancies are fully diffused through high-temperature annealing, and the diamond film with the high NV color center strength is obtained. Therefore, the diamond film with high NV color center strength is prepared. The problems that the NV color center diamond film prepared by the MPCVD method is low in color center strength and poor in optical performance are solved, and the NV color center fluorescence intensity and the color center application value of the MPCVD diamond film are improved.

Description

Technical Field

[0001] The present invention belongs to the field of NV color center diamond film materials, and in particular to a diamond film surface modification technology, which can greatly improve the NV color center strength of diamond prepared by MPCVD. Specifically, it is a method for preparing a diamond film with high NV color center strength by MPCVD; it uses a nitrogen-doped micron diamond film prepared by MPCVD, uses reactive ion etching technology to modify the surface of the diamond film, and then performs high-temperature vacuum annealing to form a diamond film with high NV color center strength. Background Art

[0002] In recent years, with the continuous deepening of related research, diamond NV color centers have been widely used in high-precision imaging, microscopic physical field detection and other fields due to their excellent mechanical and optical properties and special quantum properties, playing an important role. How to use the MPCVD method to prepare high-strength NV color center diamond films has become a difficult problem that researchers need to solve urgently.

[0003] MPCVD uses microwave energy to ionize the mixed gas into active groups, which react on the substrate surface to deposit diamond films. The advantages of this method are easy operation, fast deposition rate, and the prepared diamond film has few impurities and high quality; the disadvantage of this method is that it cannot accurately control the location of nitrogen vacancies, and the diamond vacancies formed by deposition are few and difficult to form color centers with nitrogen atoms, resulting in extremely low yield of color centers. It is necessary to combine irradiation or ion implantation and annealing and other subsequent processes to achieve high NV color center intensity. Summary of the invention

[0004] The purpose of the present invention is to address the defects of low color center intensity and poor optical properties of NV color center diamond films prepared by the existing MPCVD method. Based on the existing preparation process, an MPCVD diamond film preparation method with high NV color center intensity is invented. The method is combined with reactive ion etching technology to form an MPCVD diamond film with high color center intensity and excellent color center optical properties.

[0005] The technical solution of the present invention is: A method for preparing a diamond film with high NV color center strength by MPCVD, characterized in that it comprises the following steps: Step 1: polishing the substrate with a silica sol solution for at least 30 minutes to remove the oxide layer on the surface of the substrate; Step 2: placing the substrate in a diamond powder acetone suspension for ultrasonic oscillation treatment. The scratching effect between the substrate and the diamond powder causes a large number of microscopic defects on the substrate surface, while planting the crystal. The substrate is then ultrasonically cleaned in anhydrous ethanol for 5 to 10 minutes. Step 3, placing the processed substrate in an MPCVD device to grow a nitrogen-doped micron diamond film; Step 4: Use MPCVD equipment to modify the surface of the prepared nitrogen-doped micron diamond film by reactive ion etching (RIE) to provide structural conditions for improving the strength of NV color centers. After the etching is completed, place it in anhydrous ethanol for ultrasonic cleaning for 5 to 10 minutes. Step 5: Place the sample obtained in the above step in a muffle furnace for high temperature vacuum annealing for 2 h±15 min to allow the vacancies to fully diffuse and obtain a diamond film material with high NV color center intensity.

[0006] The silica sol solution is a silica sol solution with a particle size of 100 nm and a concentration of 40%, and the polishing cloth used is a metallographic real silk velvet polishing cloth.

[0007] The diamond powder used in the substrate ultrasonic crystal planting has a particle size of 0.2-1 μm, a ratio concentration of 3-6 g diamond powder / 100 ml acetone, and a crystal planting time of 30-60 min; the anhydrous ethanol ultrasonic cleaning time is 10-15 min; and compressed nitrogen is used to blow dry the substrate surface for subsequent use.

[0008] The deposition parameters of the nitrogen-doped micron diamond film prepared by MPCVD are as follows: the background vacuum in the vacuum reaction chamber reaches below 1 Pa to ensure the purity of the reaction gas, and the gas CH 4 / H 2 / N 2 , the total gas flux is 200 sccm, CH 4 The flux ratio is 5%, H 2 The flux accounts for 94.5% to 93%, N 2 The flux ratio is 0.5% to 2%, the deposition temperature is 850 to 900°C, the reaction gas pressure is 12 kPa, the microwave power is 15 kW, the deposition time is 2 h±15 min, and the substrate bias is turned on at -120 to -200 V in the initial stage of deposition. The bias is turned on for no less than 30 min to increase the nucleation rate.

[0009] The MPCVD equipment described above performs reactive ion etching surface modification on nitrogen-doped micron diamond films: the background vacuum in the vacuum reaction chamber is evacuated to below 1 Pa; the microwave source power is 800 W; the reaction gas is H 2 and Ar, H 2 The gas flow rate of is 20-40 sccm, the gas flow rate of Ar is 10-30 sccm, the reaction gas pressure is 1.2-1.8 kPa, the substrate bias is -120-200 V, and the etching time is 1h±5min.

[0010] The high temperature vacuum annealing parameters in the muffle furnace are as follows: the substrate is placed in a crucible, the crucible is placed in a muffle furnace, and the vacuum is evacuated to 5×10 -3Pa, heating temperature to 600 ~ 700 ℃, high temperature annealing for 2 h ± 15min.

[0011] The substrate is a silicon wafer.

[0012] The beneficial effects of the present invention are: The present invention combines reactive ion etching technology to improve the color center yield of color center diamond film prepared by MPCVD method, performs surface modification on diamond film by reactive ion etching, and then performs high temperature vacuum annealing to prepare diamond film with high NV color center strength.

[0013] The diamond surface modification of the present invention has the following benefits for the color center diamond film: (1) the diamond surface micro-nano structure can effectively limit the position of the color center, prevent the color center from agglomerating, and affect the color center from playing its optical role; (2) the diamond surface micro-nano structure can be used as an optical cavity to effectively increase the fluorescence intensity of the color center and improve the application value of the color center; (3) the diamond surface micro-nano structure can actively penetrate the sample and realize its application in the field of biological imaging; (4) by increasing the contact area between the film and the surrounding environment, the effect of annealing on improving the color center yield is more significant. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] Figure 1 It is a process flow chart of reactive ion etching of the present invention.

[0015] Figure 2 This is a surface morphology diagram of the nitrogen-doped micron diamond film of the present invention.

[0016] Figure 3 This is a surface morphology diagram of the surface-modified diamond film of the present invention.

[0017] Figure 4 It is the PL spectrum diagram of the diamond film before and after the surface modification of the present invention. DETAILED DESCRIPTION

[0018] The present invention will be further described below in conjunction with the embodiments and drawings.

[0019] like Figure 1-Figure 4 shown.

[0020] A method for preparing a diamond film with high NV color center strength by MPCVD, such as Figure 1 As shown, it includes the following steps: Step 1: polish the silicon wafer substrate with a metallographic silk velvet polishing cloth and a silica sol solution with a particle size of 100 nm and a molar concentration of 40% ± 5% for at least 30 min; Step 2: Place the silicon wafer in a suspension of 0.2-1 μm diamond powder in acetone (with a ratio of 3-6 g diamond powder / 100 ml acetone) for 30-60 min of ultrasonic vibration crystal planting, then ultrasonically clean it in anhydrous ethanol for 5-10 min, and use compressed nitrogen to blow dry the surface of the silicon wafer; Step 3: Place the processed silicon wafer in the MPCVD equipment to grow nitrogen-doped micron diamond film. The specific parameters are: the background vacuum degree in the vacuum reaction chamber reaches below 1 Pa to ensure the purity of the reaction gas, and the gas CH 4 / H 2 / N 2 , the total gas flux is 200 sccm, CH 4 The flux ratio is 5%, H 2 The flux accounts for 94.5% to 93%, N 2 The flux ratio is 0.5% to 2%, the deposition temperature is 850 to 900 °C, the reaction gas pressure is 12 kPa, the microwave power is 15 kW, the deposition time is 2 h ± 15 min, the substrate bias is turned on at the initial stage of deposition at -120 to -200 V, and the bias is applied for at least 30 min; Figure 2 The surface morphology of the nitrogen-doped micronized diamond film shown; Step 4: Use MPCVD equipment to modify the surface of the prepared nitrogen-doped micron diamond film using reactive ion etching (RIE). The specific parameters are: the background vacuum in the vacuum reaction chamber is evacuated to below 1 Pa; the microwave source power is 800 W; the reaction gas is H 2 and Ar, H 2 The gas flow rate of is 20-40 sccm, the gas flow rate of Ar is 10-30 sccm, the reaction gas pressure is 1.2-1.8 kPa, the substrate bias is -120--200 V, the etching time is 1h±5min, and after the etching is completed, it is placed in anhydrous ethanol for ultrasonic cleaning for 5-10 min; the following is obtained: Figure 3 The surface modified diamond film shown; Step 5: Place the sample obtained in the above step in a muffle furnace for high temperature vacuum annealing. The specific annealing parameters are: vacuumize to 5×10 -3 Pa, heating temperature to 600 ~ 700 ℃, high temperature annealing for 2 h ± 15 min.

[0021] The PL spectra of the diamond film before and after surface modification prepared by the above steps are shown in Figure 4 shown.

[0022] Example 1.

[0023] 1. Use a 0.5 mm thick silicon wafer, an automatic polishing machine, a metallographic silk velvet polishing cloth, and a silica sol solution with a particle size of 100 nm (concentration 40%) to polish the silicon wafer for 30 min at a polishing speed of 180 r / min, and then clean it with deionized water.

[0024] 2. Mix 30 ml suspension of 0.5 μm diamond powder and acetone at a ratio of 3 g diamond powder / 100 ml acetone, place the silicon wafer in the suspension, and ultrasonically vibrate the wafer for 40 min at 50 °C. Then, ultrasonically clean the wafer in anhydrous ethanol for 5 to 10 min, and use compressed nitrogen to blow dry the surface of the silicon wafer.

[0025] 3. Place the processed silicon wafer on the MPCVD sample stage, raise the sample stage, evacuate to below 1 Pa, close the roughing valve, and open the automatic pressure regulating valve. 2 50 sccm, wait until the gas pressure rises to 0.8 kPa, turn on the microwave power, the initial power is 600 W, and gradually increase the H 2 When the microwave power reached 15 kW, the pressure was 12 kPa, and the temperature reached 860 °C, CH 4 and N 2 , CH 4 / H 2 / N 2 The gas concentrations were 10 sccm / 189 sccm / 1 sccm respectively. Turn on the bias power supply and set the bias voltage to -150 V for 30 min. Turn off the bias power supply and continue deposition for 90 min. After the deposition is completed, turn off the CH 4 and N 2 Gas line, gradually reduce the gas pressure and microwave power to lower the temperature to room temperature.

[0026] 4. After the temperature drops to room temperature, turn off the microwave power supply and gas circuit, and evacuate the air to below 1 Pa. Reopen the H 2 and microwave power. Adjust the microwave power to 800 W, the gas pressure to 1.6 kPa, introduce Ar, and set the H 2 The Ar and Ar fluxes were 30 sccm and 20 sccm respectively, the substrate bias was set to -180 V, and the surface was modified for 1 h. After the modification was completed, the silicon wafer was taken out and ultrasonically cleaned with anhydrous ethanol for 5 to 10 min.

[0027] 5. Place the diamond film sample in a crucible, put the crucible into a muffle furnace, and evacuate to 5×10 -3 Pa, heating temperature to 700 ℃, vacuum high temperature annealing for 2 h.

[0028] Example 2.

[0029] 1. Use a 0.5 mm thick silicon wafer, an automatic polishing machine, a metallographic silk velvet polishing cloth, and a silica sol solution with a particle size of 100 nm (concentration 40%) to polish the silicon wafer for 30 min at a polishing speed of 180 r / min, and then clean it with deionized water.

[0030] 2. Mix 0.5 μm diamond powder and acetone in a ratio of 5 g diamond powder / 100 ml acetone to form a 30 ml suspension. Place the silicon wafer in the suspension and perform ultrasonic vibration crystal planting at 50 °C for 30 min. Then, perform ultrasonic cleaning in anhydrous ethanol for 5 to 10 min and blow dry the silicon wafer surface with compressed nitrogen.

[0031] 3. Place the processed silicon wafer on the MPCVD sample stage, raise the sample stage, evacuate to below 1 Pa, close the roughing valve, and open the automatic pressure regulating valve. 2 50 sccm, wait until the gas pressure rises to 0.8 kPa, turn on the microwave power, the initial power is 600 W, and gradually increase the H 2 When the microwave power reached 15 kW, the pressure was 12 kPa, and the temperature reached 850 °C, CH 4 and N 2 , CH 4 / H 2 / N 2 The gas concentrations were 10 sccm / 186 sccm / 4 sccm respectively. Turn on the bias power supply and set the bias voltage to -120 V for 30 min. Turn off the bias power supply and continue deposition for 90 min. After the deposition is completed, turn off the CH 4 and N 2 Gas line, gradually reduce the gas pressure and microwave power to lower the temperature to room temperature.

[0032] 4. After the temperature drops to room temperature, turn off the microwave power supply and gas circuit, and evacuate the air to below 1 Pa. Reopen the H 2 and microwave power. Adjust the microwave power to 800 W, the gas pressure to 1.8 kPa, introduce Ar, and set the H 2 The Ar and Ar fluxes were 40 sccm and 30 sccm, respectively, the substrate bias was set to -200 V, and the surface modification was performed for 1 h. After completion, the silicon wafer was removed and ultrasonically cleaned with anhydrous ethanol for 5 to 10 min.

[0033] 5. Place the diamond film sample in a crucible, put the crucible into a muffle furnace, and evacuate to 5×10 -3 Pa, heating temperature to 650 ℃, vacuum high temperature annealing for 2h.

[0034] Example 3.

[0035] 1. Use a 0.5 mm thick silicon wafer, an automatic polishing machine, a metallographic silk velvet polishing cloth, and a silica sol solution with a particle size of 100 nm (concentration 40%) to polish the silicon wafer for 30 min at a polishing speed of 180 r / min, and then clean it with deionized water.

[0036] 2. Mix 30 ml suspension of 0.5 μm diamond powder and acetone at a ratio of 6 g diamond powder / 100 ml acetone, place the silicon wafer in the suspension, and ultrasonically vibrate the wafer for 60 min at 50 °C. Then, ultrasonically clean the wafer in anhydrous ethanol for 5 to 10 min, and use compressed nitrogen to blow dry the surface of the silicon wafer.

[0037] 3. Place the processed silicon wafer on the MPCVD sample stage, raise the sample stage, evacuate to below 1 Pa, close the roughing valve, and open the automatic pressure regulating valve. 2 50 sccm, wait until the gas pressure rises to 0.8 kPa, turn on the microwave power, the initial power is 600 W, and gradually increase the H 2 When the microwave power reached 15 kW, the pressure was 12 kPa, and the temperature reached 900 °C, CH 4 and N 2 , CH 4 / H 2 / N 2 The gas concentrations were 10 sccm / 187 sccm / 3 sccm respectively. Turn on the bias power supply and set the bias voltage to -200 V for 30 min. Turn off the bias power supply and continue deposition for 90 min. After the deposition is completed, turn off the CH 4 and N 2 Gas line, gradually reduce the gas pressure and microwave power to lower the temperature to room temperature.

[0038] 4. After the temperature drops to room temperature, turn off the microwave power supply and gas circuit, and evacuate the air to below 1 Pa. Reopen the H 2 and microwave power. Adjust the microwave power to 800 W, the gas pressure to 1.2 kPa, introduce Ar, and set the H 2 The Ar and Ar fluxes were 20 sccm and 10 sccm respectively, the substrate bias was set to -120 V, and the surface modification was performed for 1 h. After completion, the silicon wafer was removed and ultrasonically cleaned with anhydrous ethanol for 5 to 10 min.

[0039] 5. Place the diamond film sample in a crucible, put the crucible into a muffle furnace, and evacuate to 5×10 -3 Pa, heating temperature to 600 ℃, vacuum high temperature annealing for 2 h.

[0040] The present invention does not involve parts that are the same as the prior art or can be implemented by using the prior art.

Claims

1. A method for preparing a diamond film with high NV color center strength by MPCVD, characterized in that: It includes the following steps: Step 1: polishing the substrate with a silica sol solution for at least 30 minutes to remove the oxide layer on the surface of the substrate; Step 2: placing the substrate in a diamond powder acetone suspension for ultrasonic oscillation treatment. The scratching effect between the substrate and the diamond powder causes a large number of microscopic defects on the substrate surface, while planting the crystal. The substrate is then ultrasonically cleaned in anhydrous ethanol for 5 to 10 minutes. Step 3, placing the processed substrate in an MPCVD device to grow a nitrogen-doped micron diamond film; Step 4: Use MPCVD equipment to modify the surface of the prepared nitrogen-doped micron diamond film by reactive ion etching (RIE) to provide structural conditions for improving the strength of NV color centers. After the etching is completed, place it in anhydrous ethanol for ultrasonic cleaning for 5 to 10 minutes. Step 5: Place the sample obtained in the above step in a muffle furnace for high temperature vacuum annealing for 2 h±15 min to allow the vacancies to fully diffuse and obtain a diamond film material with high NV color center intensity.

2. The method according to claim 1, characterized in that: The silica sol solution is a silica sol solution with a particle size of 100 nm and a concentration of 40%, and the polishing cloth used is a metallographic real silk velvet polishing cloth.

3. The method according to claim 1, characterized in that: The diamond powder used in the substrate ultrasonic crystal planting has a particle size of 0.2-1 μm, a ratio concentration of 3-6 g diamond powder / 100 ml acetone, and a crystal planting time of 30-60 min; the anhydrous ethanol ultrasonic cleaning time is 10-15 min; and compressed nitrogen is used to blow dry the substrate surface for subsequent use.

4. The method according to claim 1, characterized in that: The deposition parameters of the nitrogen-doped micron diamond film prepared by MPCVD are as follows: the background vacuum degree in the vacuum reaction chamber reaches below 1 Pa to ensure the purity of the reaction gas, and the gas CH4 / H2 / N2 is introduced, the total gas flux is 200 sccm, the CH4 flux accounts for 5%, the H2 flux accounts for 94.5% to 93%, and the N2 flux accounts for 0.5% to 2%. The deposition temperature is 850 to 900°C, the reaction gas pressure is 12 kPa, the microwave power is 15 kW, the deposition time is 2 h±15min, and the substrate bias is turned on at -120 to -200 V in the initial stage of deposition, and the bias is turned on for no less than 30 min to increase the nucleation rate.

5. The method according to claim 1, characterized in that The MPCVD equipment described herein performs reactive ion etching surface modification on nitrogen-doped micron diamond film: the background vacuum in the vacuum reaction chamber is evacuated to below 1 Pa; the microwave source power is 800 W; the reaction gases are H2 and Ar, the gas flow rate of H2 is 20 to 40 sccm, the gas flow rate of Ar is 10 to 30 sccm, the reaction gas pressure is 1.2 to 1.8 kPa, the substrate bias is -120 to -200 V, and the etching time is 1 h±5 min.

6. The method according to claim 1, characterized in that The high temperature vacuum annealing parameters in the muffle furnace are as follows: the substrate is placed in a crucible, the crucible is placed in a muffle furnace, and the vacuum is evacuated to 5×10 -3 Pa, heating temperature to 600 ~ 700 ℃, high temperature annealing for 2 h ± 15 min.

7. The method according to claim 1, characterized in that: The substrate is a silicon wafer.

Images