A method for improving the photoluminescence intensity of SiV color centers in nanodiamond films

Abstract

The present invention discloses a method for improving the photoluminescence intensity of SiV color centers in a nanodiamond film, which can rapidly and significantly enhance the photoluminescence intensity of the nanodiamond. The process of the present invention is simple and has a relatively low cost, and is of great value for improving the photoluminescence intensity of SiV color centers in the nanodiamond.

Description

Technical Field

[0001] The present invention relates to a new method for improving the photoluminescence intensity of SiV color centers in nanodiamond films Background Art

[0002] The silicon vacancy (SiV) color center in diamond has advantages such as good structural stability, strong optical stability, short excited state lifetime, and narrow zero phonon line bandwidth at room temperature. Among them, the nanodiamond film containing SiV color centers has a very broad application prospect in the fields of quantum information, nanophotonics, biological labeling, and sensing due to its emission peak avoiding biological autofluorescence and good biocompatibility

[0003] However, nanodiamond films usually contain sp 2 carbon or graphite phase, and the number of SiV color centers is limited, which will lead to a decrease in the luminescence intensity of SiV color centers in the film and a broadening of the zero phonon line (ZPL), thus limiting the application and development of SiV color centers in nanodiamond films. Researchers regulate the amount of silicon doping during chemical vapor deposition to control the Si content entering the nanodiamond film, thereby regulating the luminescence intensity of SiV color centers in the film. However, it is not that the more Si doping, the more beneficial to the improvement of the luminescence performance of SiV color centers. When the doping amount is too much, it will affect the crystal morphology and size of diamond, and at the same time form amorphous carbon on the diamond surface, resulting in the quenching phenomenon of SiV color center photoluminescence. In addition, air thermal oxidation can be used to etch sp 2 carbon in the nanodiamond film, change the surface termination state of diamond, and thus improve the luminescence intensity. The inventor previously treated the nanodiamond film by air thermal oxidation, converting the negative electron affinity induced by the termination of C-H bonds on the diamond surface into the positive electron affinity surface terminated by C=O bonds, thereby greatly improving the photoluminescence intensity of SiV color centers in the nanodiamond film (authorized patent ZL201510149396.0). However, the surface defects of nanodiamond may act as traps for the excited carriers of SiV color centers, thereby reducing the luminescence efficiency of SiV color centers inside the diamond. In addition, the luminescence intensity of SiV color centers in the film can also be improved by constructing nanostructures and resonators on the diamond surface, but its preparation process is relatively complex. Since the SiV color centers in nanodiamond and the film always show the quenching behavior of photoluminescence, it is difficult to improve its photoluminescence intensity. And in many of its application fields, it is required that the SiV color centers in nanodiamond have strong photoluminescence intensity, such as improving the accuracy of biological sensing measurement. The weak luminescence intensity of SiV color centers in nanodiamond films will seriously limit their development and application. Therefore, there is an urgent need to develop simple and reliable methods to improve the luminescence intensity of SiV color centers in nanodiamond films

[0004] In this patent, the inventors used the hot-filament chemical vapor deposition method to prepare a nanodiamond film on the surface of a single-crystalline silicon substrate. On the basis of thermal oxidation, the sample was further treated with a NaOH solution for a short time, which significantly increased the luminescence intensity of the SiV color centers in the film, and a new method for increasing the luminescence intensity of SiV color centers in nanodiamond films was proposed. Summary of the Invention

[0005] The present invention develops a new method for increasing the luminescence intensity of SiV color centers in nanodiamond films. This method uses a NaOH solution to treat the nanodiamond film on a silicon substrate for a short time, allowing silicon atoms to enter the diamond lattice to form SiV color centers, thereby significantly increasing the luminescence intensity of the SiV color centers.

[0006] To achieve the above object, the present invention adopts the following technical solutions:

[0007] The present invention provides a method for increasing the photoluminescence intensity of SiV color centers in a nanodiamond film, and the method is as follows:

[0008] S1: A single-crystalline silicon wafer is seeded with diamond micropowder to obtain a seeded silicon wafer;

[0009] The seeded silicon wafer is subjected to hot-filament chemical vapor deposition using acetone as a carbon source and a carbonized tantalum wire as a heat source to obtain a nanodiamond film;

[0010] The obtained nanodiamond film is thermally oxidized at 550 - 650 °C in an air atmosphere to obtain a single-particle layer nanodiamond film with SiV luminescence;

[0011] S2: The single-particle layer nanodiamond film with SiV luminescence obtained in step S1 is immersed in a 5 - 8% (preferably 5%) aqueous NaOH solution and heated in a water bath at 80 - 100 °C (preferably 100 °C) for 2 - 6 min (preferably 5 min). The obtained film is post-treated to obtain a nanodiamond film with enhanced photoluminescence intensity of SiV color centers.

[0012] The operation of step S1 has been described in patent ZL201510149396.0.

[0013] Specifically, the seeding in step S1 is as follows: Diamond micropowder with a particle size of 500 nm is uniformly dispersed in a solvent to obtain a seeding solution; The seeding solution is taken and the single-crystalline silicon wafer is polished on a polishing cloth for 10 - 30 min (preferably 20 min). The obtained silicon wafer is washed and dried (blown dry with a nitrogen gun) to obtain a seeded silicon wafer.

[0014] Further, the solvent is glycerol or deionized water (water in the embodiments of the present invention). Further still, the volume of the solvent is 80 - 120 mL / g based on the mass of the diamond micropowder, and is 100 mL / g in one embodiment of the present invention.

[0015] Further, the cleaning operation is as follows: Place the silicon wafer in an organic solvent for ultrasonic cleaning (manufactured by Kunshan Ultrasonic Instrument Co., Ltd., model KQ5200DE, ultrasonic for 15 min at 100W - 200W, preferably 140W), and then clean with deionized water. Further still, the organic solvent is ethanol or acetone, preferably ethanol.

[0016] Specifically, the nanodiamond film in step S1 is prepared as follows: Install a tantalum wire in the hot filament chemical vapor deposition equipment at a height of 5 - 10 mm (preferably 7 mm) from the sample stage. Acetone enters the reaction chamber in the form of hydrogen bubbling, and the flow rate of the acetone is 50 - 100 sccm (preferably 80 sccm). At the same time, pure hydrogen with a flow rate of 200 - 250 sccm (preferably 200 sccm) is introduced (to adjust the concentration of acetone). The working pressure is 5.3 - 6.0 kPa (controlled by the outflow gas); work at 7V for 5 - 10 min (preferably 10 min), 12V for 5 - 10 min (preferably 10 min), and 15V for 5 - 10 min (preferably 5 min) in sequence to complete the carbonization process of the tantalum wire;

[0017] Place the seeded silicon wafer on the sample stage, set the flow rate of pure hydrogen to 200 - 250 sccm (preferably 200 sccm), the flow rate of acetone to 80 - 100 sccm (preferably 90 sccm), the working pressure to 1.0 - 2.5 kPa (preferably 1.6 kPa), the hot filament power to 2000 - 2500W (preferably 2200W), and grow for 10 - 15 min (preferably 13 min) to obtain the nanodiamond film.

[0018] Specifically, the thermal oxidation treatment in step S1 is as follows: Place the nanodiamond film in a muffle furnace and perform thermal oxidation treatment at 550 - 650 °C for 15 - 30 min (preferably perform thermal oxidation treatment at 600 °C for 20 min) in an air atmosphere to obtain the single - particle - layer nanodiamond film with SiV luminescence.

[0019] In one embodiment of the present invention, after seeding, the single - crystal silicon wafer is cut into a substrate material with dimensions of 10 × 10 × 0.5 mm and then placed in the hot filament chemical vapor deposition equipment.

[0020] The hot filament chemical vapor deposition equipment is purchased from Shanghai Jiaoyou Diamond Coating Company, model JUHFCVD001.

[0021] Further, the post-treatment in step S2 is as follows: the film is successively cleaned with deionized water and ethanol, and dried (blown dry with a nitrogen gun) to obtain the nanodiamond film with enhanced photoluminescence intensity of SiV color centers.

[0022] Compared with the existing processes for improving the luminescence intensity of SiV color centers in nanodiamonds, the beneficial effects of the present invention are as follows: (1) This method has low requirements for equipment, simple process and easy operation; (2) It greatly improves the luminescence intensity of SiV color centers in the nanodiamond film; (3) The treatment time is short, and the luminescence intensity of SiV color centers can be rapidly increased. Description of the Drawings

[0023] Figure 1 SEM image of Example 1 (NaOH treatment for 2 min).

[0024] Figure 2 Raman spectrum of Example 1 (NaOH treatment for 2 min).

[0025] Figure 3 PL spectrum of Example 1 (NaOH treatment for 2 min).

[0026] Figure 4 SEM image of Example 2 (NaOH treatment for 5 min).

[0027] Figure 5 Raman spectrum of Example 2 (NaOH treatment for 5 min).

[0028] Figure 6 PL spectrum of Example 2 (NaOH treatment for 5 min).

[0029] Figure 7 SEM image of Example 3 (NaOH treatment for 6 min).

[0030] Figure 8 Raman spectrum of Example 3 (NaOH treatment for 6 min).

[0031] Figure 9 PL spectrum of Example 3 (NaOH treatment for 6 min).

[0032] Figure 10 SEM image of Comparative Example 1 (untreated sample).

[0033] Figure 11 Raman spectrum of Comparative Example 1 (untreated sample).

[0034] Figure 12 PL spectrum of Comparative Example 1 (untreated sample).

[0035] Figure 13 SEM image of Comparative Example 2 (NaOH treatment for 7 min).

[0036] Figure 14 Raman spectrum of Comparative Example 2 (NaOH treatment for 7 min).

[0037] Figure 15 PL spectrum of Comparative Example 2 (NaOH treatment for 7 min). Detailed implementation manners

[0038] The present invention will be further described below through specific examples, but the protection scope of the present invention is not limited thereto.

[0039] Example 1

[0040] (1) Pretreatment of silicon wafer: Diamond micropowder with a size of 500 nm and deionized water were uniformly mixed at a ratio of 1 g:100 ml to prepare a seed crystal solution. The single-crystal silicon wafer was divided into pieces of 10 mm * 10 mm. The seed crystal solution was taken and polished on a polishing cloth for 20 min for seed crystal treatment. The seeded silicon wafer was put into ethanol for ultrasonic cleaning (manufactured by Kunshan Ultrasonic Instrument Co., Ltd., model KQ5200DE, 140 W ultrasonic for 15 min), then washed with deionized water and dried (blown dry with a nitrogen gun) to obtain a pretreated silicon wafer.

[0041] (2) Preparation of nanodiamond film: A tantalum wire tooling was used. The hydrogen flow rate of the gas source system was controlled to be 200 sccm, and the hydrogen flow rate in acetone was 80 sccm. The pressure in the reaction chamber was adjusted to be stable at 5.7 kPa. The tantalum wire carbonization process was completed by setting the voltage to 7 V for 10 min, 12 V for 10 min, and 15 V for 5 min in sequence. Then the pretreated single-crystal silicon wafer was put into the HFCVD chamber, with the hydrogen flow rate set to 200 sccm, the hydrogen flow rate in acetone to 90 sccm, the working pressure to 1.6 kPa, and the hot wire power to 2200 W, and grown for 13 min to obtain a nanodiamond film.

[0042] (3) Thermal oxidation treatment: The sample obtained in step (2) was put into a muffle furnace and subjected to thermal oxidation treatment at 600 °C for 20 min, and the sample was taken out after the thermal oxidation was completed.

[0043] (4) NaOH treatment: An aqueous NaOH solution with a mass fraction of 5% was prepared. Under the condition of water bath heating at 100 °C, the sample treated in step (3) was put into 2 ml of the NaOH solution for 2 min. After the treatment, the sample was successively washed with deionized water and ethanol, and the sample was dried (blown dry with a nitrogen gun).

[0044] The surface morphology and photoluminescence intensity of the samples after the experiment were characterized by field emission scanning electron microscopy (FESEM) and laser Raman spectrometer (Raman).

[0045] Figure 1 For the SEM image in Example 1, it can be observed that the surface morphology of the film after being treated with 5% NaOH solution for 2 min has no obvious change compared with the nanodiamond film without NaOH treatment. The film is not dense and does not completely cover the substrate.

[0046] Figure 2 For the Raman spectrum in Example 1, it shows the characteristics of nanodiamond, and there is an obvious diamond characteristic peak at 1332 cm -1 There is an obvious diamond characteristic peak at this position. Compared with before the NaOH treatment, the area of the diamond peak has no obvious change.

[0047] Figure 3 For the PL spectrum corresponding to the Raman spectrum in Example 1. Figure 3 The ordinate in it is the intensity ratio obtained after normalization with the absolute intensity of the diamond characteristic peak at 572.5 nm as the standard. In the nanodiamond film after being treated with NaOH for 2 min, the SiV color center shows a sharp zero phonon line near 738.5 nm. The intensity ratio of the zero phonon line of the SiV color center to the diamond characteristic peak, that is, the relative luminescence intensity, is 21.01. Compared with Figure 12 the PL spectrum of the nanodiamond film without NaOH treatment in it, its relative luminescence intensity has increased by 27.6%.

[0048] Example 2

[0049] (1) Pretreatment of silicon wafer: Diamond micropowder with a size of 500 nm and deionized water were uniformly mixed at a ratio of 1 g:100 ml to prepare a seed crystal solution. The single crystal silicon wafer was divided into pieces of 10 mm * 10 mm. The seed crystal solution was taken and polished on a polishing flannel for 20 min for seed crystal treatment. The silicon wafer after seed crystal treatment was put into ethanol and ultrasonically cleaned (manufactured by Kunshan Ultrasonic Instrument Co., Ltd., model KQ5200DE, 140 W ultrasonic for 15 min), then cleaned with deionized water and dried (blown dry with a nitrogen gun) to obtain the pretreated silicon wafer.

[0050] (2) Preparation of nanodiamond film: Using a tantalum wire tooling, control the gas source system to set the hydrogen flow rate to 200 sccm, the hydrogen flow rate in acetone to 80 sccm, and adjust the pressure in the reaction chamber to be stable at 5.7 kPa; sequentially set the voltage to 7 V for 10 min, 12 V for 10 min, and 15 V for 5 min to complete the tantalum wire carbonization process. Then place the pretreated single-crystalline silicon wafer into the HFCVD chamber, set the hydrogen flow rate to 200 sccm, the hydrogen flow rate in acetone to 90 sccm, the working pressure to 1.6 kPa, the hot wire power to 2200 W, and grow for 13 min to obtain the nanodiamond film.

[0051] (3) Thermal oxidation treatment: Place the sample obtained in step (2) into a muffle furnace and perform thermal oxidation treatment at 600 °C for 20 min, and then take out the sample after the thermal oxidation ends.

[0052] (4) NaOH treatment: Prepare an aqueous NaOH solution with a mass fraction of 5%, and place the silicon wafer treated in step (3) into 2 ml of the NaOH solution under the condition of water bath heating at 100 °C for 5 min. After the treatment, place the silicon wafer into deionized water and ethanol for cleaning in sequence, and dry the sample (blow dry with a nitrogen gun).

[0053] Use FESEM and Raman to characterize the surface morphology and photoluminescence intensity of the sample after the experiment.

[0054] Figure 4 For the SEM image in Example 2, due to the short treatment time, it can be observed that for the sample treated with 5% NaOH solution for 5 min, compared with the sample without NaOH treatment, some small particles in the film fall off.

[0055] Figure 5 For the Raman spectrum in Example 2, there is no obvious difference in the peak areas and full-width at half-maximum of the diamond peak, D peak, and G peak in the Raman spectrum compared with the sample without NaOH treatment. It shows that after the sample is treated with NaOH solution for 5 min, the phase of the sample does not change.

[0056] Figure 6 For the PL spectrum corresponding to the Raman spectrum of the SiV color center in Example 2. Figure 6 The ordinate is the intensity ratio obtained after normalization with the absolute intensity of the diamond characteristic peak at 572.5 nm as the standard. The SiV color center in the nanodiamond film after treatment with NaOH solution for 5 min shows a sharp zero phonon line near 738.5 nm. The intensity ratio of the zero phonon line of the SiV color center to the diamond characteristic peak, that is, the relative luminescence intensity, is 29.66. Compared with Figure 12 the PL spectrum of the nanodiamond film without NaOH treatment in

[0057] Example 3

[0058] (1) Silicon wafer pretreatment: Diamond micropowder with a size of 500 nm is uniformly mixed with deionized water at a ratio of 1 g:100 ml to prepare a seed crystal solution. The single-crystal silicon wafer is divided into pieces of 10 mm * 10 mm. The seed crystal solution is taken and polished on the polishing flannel for 20 min for seed crystal treatment. The seeded silicon wafer is ultrasonically cleaned in ethanol (manufactured by Kunshan Ultrasonic Instrument Co., Ltd., model KQ5200DE, 140 W ultrasonic for 15 min), then cleaned with deionized water and dried (blown dry with a nitrogen gun) to obtain a pretreated silicon wafer.

[0059] (2) Preparation of nanodiamond film: Tantalum wire tooling, controlling the gas source system to set the hydrogen flow rate to 200 sccm, the hydrogen flow rate in acetone to 80 sccm, and adjusting the pressure in the reaction chamber to be stable at 5.7 kPa; successively setting the voltage to 7 V for 10 min, 12 V for 10 min, and 15 V for 5 min to complete the tantalum wire carbonization process. Then the pretreated single-crystal silicon wafer is placed in the HFCVD chamber, setting the hydrogen flow rate to 200 sccm, the hydrogen flow rate in acetone to 90 sccm, the working pressure to 1.6 kPa, and the hot wire power to 2200 W, and growing for 13 min to obtain a nanodiamond film.

[0060] (3) Thermal oxidation treatment: The sample obtained in step (2) is placed in a muffle furnace and thermally oxidized at 600 °C for 20 min, and the sample is taken out after the thermal oxidation ends.

[0061] (4) NaOH treatment: Prepare an aqueous NaOH solution with a mass fraction of 5%. Under the condition of water bath heating at 100 °C, the silicon wafer treated in step (3) is placed in 2 ml of NaOH solution for 6 min. After the treatment, the silicon wafer is successively cleaned in deionized water and ethanol and dried (blown dry with a nitrogen gun).

[0062] The surface morphology and photoluminescence intensity of the sample after the experiment are characterized by FESEM and Raman.

[0063] Figure 7 The SEM image of Example 3. Since diamond does not react with NaOH, short-term NaOH treatment will not affect the surface morphology of the film, but only cause some particles on the film surface to fall off.

[0064] Figure 8 The Raman spectrum of Example 3. Compared with the sample treated with NaOH for 5 min, after treatment for 6 min, its Raman spectrum has no obvious change.

[0065] Figure 9It is the PL spectrum corresponding to the Raman spectrum of the SiV color center in Example 3. Figure 9 The ordinate is the intensity ratio obtained by normalizing with the absolute intensity of the diamond characteristic peak at 572.5 nm as the standard. The SiV color center in the nanodiamond film after being treated with NaOH solution for 6 min shows a sharp zero phonon line near 738.5 nm. The intensity ratio of the zero phonon line of the SiV color center to the diamond characteristic peak, that is, the relative luminescence intensity, is 27.65. Compared with Figure 12 the untreated nanodiamond film in

[0066] Comparative Example 1

[0067] (1) Silicon wafer pretreatment: Diamond micropowder with a size of 500 nm and deionized water were uniformly mixed at a ratio of 1 g:100 ml to prepare a seed crystal solution. The single crystal silicon wafer was divided into pieces of 10 mm * 10 mm. The seed crystal solution was taken and polished on a polishing cloth for 20 min for seed crystal treatment. The seeded silicon wafer was put into ethanol for ultrasonic cleaning (manufactured by Kunshan Ultrasonic Instrument Co., Ltd., model KQ5200DE, 140 W ultrasonic for 15 min), then washed with deionized water and dried (blown dry with a nitrogen gun) to obtain a pretreated silicon wafer.

[0068] (2) Preparation of nanodiamond film: A tantalum wire tooling was used. The hydrogen flow rate of the gas source system was controlled to be 200 sccm, and the hydrogen flow rate in acetone was 80 sccm. The pressure in the reaction chamber was adjusted to be stable at 5.7 kPa. The tantalum wire carbonization process was completed by setting the voltage to 7 V for 10 min, 12 V for 10 min, and 15 V for 5 min in sequence. Then the pretreated single crystal silicon wafer was put into the HFCVD chamber. The hydrogen flow rate was set to 200 sccm, the hydrogen flow rate in acetone was 90 sccm, the working pressure was 1.6 kPa, and the hot wire power was 2200 W. After growing for 13 min, a nanodiamond film was obtained.

[0069] (3) Thermal oxidation treatment: The sample obtained in step (2) was put into a muffle furnace and thermally oxidized at 600 °C for 20 min. After the thermal oxidation was completed, the sample was taken out.

[0070] FESEM and Raman were used to characterize the surface morphology and photoluminescence intensity of the sample after the experiment.

[0071] Figure 10 It is the SEM image of the untreated sample. The surface of the film is not dense, and part of the substrate is exposed.

[0072] Figure 11 It is the Raman spectrum of the untreated sample, showing typical nanodiamond characteristics.

[0073] Figure 12 The PL spectrum corresponding to the Raman spectrum of the untreated sample. Figure 12 The ordinate in it is the intensity ratio obtained after normalization with the absolute intensity of the diamond characteristic peak at 572.5 nm as the standard. In the thermally oxidized nanodiamond film, the SiV color center exhibits a sharp zero phonon line near 738.5 nm, and the intensity ratio of the zero phonon line of the SiV color center to the diamond characteristic peak, that is, the relative luminescence intensity, is 16.46.

[0074] Comparative Example 2

[0075] (1) Silicon wafer pretreatment: Diamond micropowder with a size of 500 nm is uniformly mixed with deionized water at a ratio of 1 g:100 ml to prepare a seed crystal solution. The single crystal silicon wafer is cut into pieces of 10 mm * 10 mm, and the seed crystal solution is taken to polish on the polishing flannelette for 20 min for seed crystal treatment. The seeded silicon wafer is put into ethanol for ultrasonic cleaning (manufactured by Kunshan Ultrasonic Instrument Co., Ltd., model KQ5200DE, 140 W ultrasonic for 15 min), then cleaned with deionized water and dried (blown dry with a nitrogen gun) to obtain the pretreated silicon wafer.

[0076] (2) Preparation of nanodiamond film: Tantalum wire tooling, controlling the gas source system to set the hydrogen flow rate at 200 sccm, the hydrogen flow rate in acetone at 80 sccm, and adjusting the pressure in the reaction chamber to be stable at 5.7 kPa; successively setting the voltage at 7 V for 10 min, 12 V for 10 min, and 15 V for 5 min to complete the tantalum wire carbonization process. Then the pretreated single crystal silicon wafer is put into the HFCVD chamber, setting the hydrogen flow rate at 200 sccm, the hydrogen flow rate in acetone at 90 sccm, the working pressure at 1.6 kPa, and the hot wire power at 2200 W, and growing for 13 min to obtain the nanodiamond film.

[0077] (3) Thermal oxidation treatment: The sample obtained in step (2) is put into a muffle furnace and subjected to thermal oxidation treatment at 600 °C for 20 min, and the sample is taken out after the thermal oxidation ends.

[0078] (4) NaOH treatment: Prepare an aqueous NaOH solution with a mass fraction of 5%, and put the sample treated in step (3) into 2 ml of NaOH solution for treatment for 7 min under the condition of water bath heating at 100 °C. After the treatment ends, the sample is successively put into deionized water and ethanol for cleaning, and the sample is dried (blown dry with a nitrogen gun).

[0079] The surface morphology and photoluminescence intensity of the sample after the FESEM and Raman characterization experiments are adopted.

[0080] Figure 13 It is the SEM image in Comparative Example 2. Most of the diamond film falls off from the substrate, exposing a large area of the silicon substrate.

[0081] Figure 14 For the Raman spectrum in Comparative Example 2, the Raman spectrum shows a sharp silicon peak at 520.5 cm -1 indicating the detachment of single-crystalline diamond on the silicon substrate under NaOH treatment.

[0082] Figure 15 It is the PL spectrum corresponding to the Raman spectrum in Comparative Example 2. Figure 15 The ordinate in it is the intensity ratio obtained by normalizing with the absolute intensity of the diamond characteristic peak at 572.5 nm as the standard. After treatment, the SiV color center in the nanodiamond film on the silicon wafer shows a sharp zero phonon line near 738.5 nm. The intensity ratio of the zero phonon line of the SiV color center to the diamond characteristic peak, that is, the relative luminescence intensity, is only 1.1, and the luminescence intensity is very weak, unable to achieve the purpose of improving the luminescence intensity of the SiV color center in the nanodiamond film.

Claims

1. A method for improving the photoluminescence intensity of SiV color centers in a nanodiamond film, characterized in that The method is as follows: S1: A single-crystalline silicon wafer is seeded with diamond micropowder to obtain a silicon wafer with seeds; The silicon wafer with seeds is subjected to hot-filament chemical vapor deposition using acetone as the carbon source and a carbonized tantalum wire as the heat source. The tantalum wire is installed in the hot-filament chemical vapor deposition equipment at a height of 5 - 10 mm from the sample stage. Acetone enters the reaction chamber in the form of hydrogen bubbling. The flow rate of acetone is 50 - 100 sccm, and at the same time, pure hydrogen with a flow rate of 200 - 250 sccm is introduced. The working pressure is 5.3 - 6.0 kPa. Sequentially, it works at 7 V for 5 - 10 min, 12 V for 5 - 10 min, and 15 V for 5 - 10 min to complete the carbonization process of the tantalum wire. The silicon wafer with seeds is placed on the sample stage, and the flow rate of pure hydrogen, the flow rate of acetone, the working pressure, and the hot-filament power are set to perform hot-filament chemical vapor deposition to obtain a nanodiamond film. The obtained nanodiamond film is thermally oxidized at 550 - 650 °C for 15 - 30 min in an air atmosphere to obtain a single-particle layer nanodiamond film with SiV color center luminescence; S2: The single-particle layer nanodiamond film with SiV color center luminescence obtained in step S1 is immersed in a 5 - 8% NaOH aqueous solution and heated in a water bath at 80 - 100 °C for 2 - 6 min. The obtained film is post-treated to obtain a nanodiamond film with enhanced SiV color center photoluminescence intensity.

2. The method for enhancing the photoluminescence intensity of the SiV color center in a nanodiamond film as described in claim 1, wherein: The seeding method in step S1 is as follows: Diamond micropowder with a particle size of 500 nm is uniformly dispersed in a solvent to obtain a seeding solution. The seeding solution is taken and the single-crystalline silicon wafer is polished on a polishing cloth for 10 - 30 min. The obtained silicon wafer is washed and dried to obtain a silicon wafer with seeds.

3. The method for improving the photoluminescence intensity of SiV color centers in a nanodiamond film according to claim 2, characterized in that: The solvent is glycerol or deionized water.

4. The method for increasing the photoluminescence intensity of SiV color centers in a nanodiamond film according to claim 2, characterized in that: The volume of the solvent is 80 - 120 mL / g based on the mass of the diamond micropowder.

5. The method for improving the photoluminescence intensity of SiV color centers in a nanodiamond film according to claim 2, characterized in that: The washing operation is as follows: The silicon wafer is ultrasonically washed in an organic solvent and then washed with deionized water. The organic solvent is ethanol or acetone.

6. The method for improving the photoluminescence intensity of SiV color centers in a nanodiamond film according to claim 1, characterized in that: In step S1, the silicon wafer with seeds is placed on the sample stage, the flow rate of pure hydrogen is set to 200 - 250 sccm, the flow rate of acetone is 80 - 100 sccm, the working pressure is 1.0 - 2.5 kPa, and the hot-filament power is 2000 - 2500 W. Growth is carried out for 10 - 15 min to obtain the nanodiamond film.

7. The method for improving the photoluminescence intensity of SiV color centers in a nanodiamond film according to claim 1, characterized in that: The thermal oxidation treatment in step S1 is as follows: The nanodiamond film is placed in a muffle furnace and thermally oxidized at 550 - 650 °C for 15 - 30 min in an air atmosphere to obtain the single-particle layer nanodiamond film with SiV luminescence.

8. The method for increasing the photoluminescence intensity of SiV color centers in a nanodiamond film according to claim 1, characterized in that: The post-treatment in step S2 is as follows: The film is successively washed with deionized water and ethanol and dried to obtain the nanodiamond film with enhanced SiV color center photoluminescence intensity.

9. The method for improving the photoluminescence intensity of SiV color centers in a nanodiamond film according to claim 1, characterized in that: The concentration of the NaOH aqueous solution in step S2 is 5%.

10. The method for improving the photoluminescence intensity of SiV color centers in a nanodiamond film as claimed in claim 1, wherein: The temperature of the water bath heating treatment described in step S2 is 100 °C, and the time is 5 minutes.

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