Preparation method and nitrogen-vacancy-containing color center diamond

Abstract

The invention relates to the technical field of solid spin sensing, and provides a preparation method of a diamond containing a nitrogen vacancy color center and the nitrogen vacancy color center diamond obtained through the method, the preparation process of the diamond NV color center is subjected to step and parameter optimization, the conversion efficiency of converting nitrogen atoms in the diamond into the nitrogen vacancy color center is improved, and the nitrogen vacancy color center is obtained. And meanwhile, the cleanliness of the surface of the diamond is guaranteed.

Description

Technical Field

[0001] The invention relates to the technical field of solid-state spin sensing, and in particular to a method for preparing a nitrogen vacancy color center diamond and the nitrogen vacancy color center diamond obtained by the method. Background Art

[0002] Diamond NV color center refers to a specific defect structure in diamond, which is formed by a vacancy and a nitrogen atom in adjacent positions in the diamond lattice. The "NV" here is the abbreviation of "Nitrogen-Vacancy", which means nitrogen vacancy color center.

[0003] Diamond NV centers have important applications in quantum information and quantum computing because they exhibit some unique quantum properties. For example, NV centers can act as an effective quantum bit with long-lived quantum coherence and optical operability. These properties make diamond NV centers have potential applications in quantum information processing and quantum sensing. In addition, the electron spin of NV centers can interact with the environment, which can be used for high-precision magnetic field and magnetic field detection at the nanoscale.

[0004] However, other defects in diamond will interfere with the sensing of nitrogen vacancy color centers, and it is necessary to control the nitrogen content during the diamond growth process through chemical vapor deposition, and increase the number of nitrogen vacancy color centers, a point defect, to increase the sensitivity of the sensor. However, the current relevant diamond NV color center preparation technology still produces products with more impurity defects (referring to defects other than NV color centers). Summary of the invention

[0005] The present invention aims to provide a method for preparing diamond containing nitrogen vacancy color centers, so as to increase the number of NV color centers in diamond, reduce impurity defects, and improve the cleanliness of the diamond surface.

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

[0007] A method for preparing diamond containing nitrogen vacancy color centers comprises the following steps:

[0008] (1) providing an initial single crystal diamond containing nitrogen;

[0009] (2) irradiating the initial single crystal diamond to obtain a pretreated single crystal diamond containing vacancy defects;

[0010] (3) performing a first cleaning on the pretreated single crystal diamond to obtain a pretreated single crystal diamond after the first cleaning, wherein the first cleaning is performed by sequentially using acetone and isopropanol;

[0011] (4) subjecting the pretreated single crystal diamond after the first cleaning to a high temperature annealing treatment to obtain a semi-finished single crystal diamond containing a large number of dense nitrogen vacancy color centers, wherein the high temperature annealing treatment is performed in a vacuum environment;

[0012] (5) performing pickling treatment on the semi-finished single crystal diamond to obtain a pickled semi-finished single crystal diamond;

[0013] (6) The semi-finished single crystal diamond after the acid washing is cleaned for a second time to obtain a finished single crystal diamond, wherein the second cleaning is performed by successively using deionized water, acetone and isopropanol for cleaning, and then drying the semi-finished single crystal diamond after cleaning.

[0014] Furthermore, the irradiation process uses a high-energy electron beam with an energy of 8 to 10 MeV and an irradiation time of 11 to 33 hours.

[0015] Furthermore, the irradiation treatment process uses a copper container to place the initial single crystal diamond, and a water cooling component is configured around the copper container.

[0016] Furthermore, the initial single crystal diamond is grown by chemical vapor deposition, has a thickness of ≤300 um, and a nitrogen content of ≥50 ppm.

[0017] Furthermore, during high temperature annealing, the annealing temperature is 850°C-1100°C. Furthermore, during high temperature annealing, the temperature rise rate does not exceed 10°C per minute, the temperature drop rate does not exceed 10°C per minute, and the temperature is kept for a certain time when it is heated to the set temperature, and then it is heated to the annealing temperature, and the set temperature is based on 1 / 2 of the annealing temperature, and the upper and lower deviations do not exceed 50°C.

[0018] Furthermore, in the pickling treatment step, the pickling temperature of the pickling solution is 220° C., and the pickling solution is a mixed solution of HNO 3 , H 2 SO 4 and HClO 4 prepared in a ratio of 1:1:1.

[0019] Furthermore, during high temperature annealing treatment, the pressure of the vacuum environment is <1*10-3Pa.

[0020] In addition, the present invention also provides a diamond containing a nitrogen vacancy color center, which is prepared by the preparation method as described above.

[0021] Compared with the prior art, the beneficial effects of the present invention are as follows: the present invention optimizes the steps and parameters of the preparation process of diamond NV color centers, improves the conversion efficiency of nitrogen atoms in diamond into nitrogen vacancy color centers, and at the same time ensures the cleanliness of the diamond surface. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings required for describing the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other accompanying drawings can be obtained based on these accompanying drawings without paying creative work.

[0023] Figure 1 is a flow chart of the preparation method in this embodiment;

[0024] Figure 2 is the ODMR spectrum of the sample in this implementation;

[0025] Figure 3 This is a schematic diagram of the pickling device in this implementation;

[0026] Figure 4 This is a schematic diagram of a vacuum high temperature annealing device in this embodiment;

[0027] Figure 5 : is the temperature variation curve of the tube furnace in this implementation. DETAILED DESCRIPTION

[0028] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0029] Unless otherwise specifically stated, the relative arrangement, numerical expressions and numerical values ​​of the parts and steps set forth in these embodiments do not limit the scope of the present application. At the same time, it should be understood that, for ease of description, the sizes of the various parts shown in the accompanying drawings are not drawn according to the actual proportional relationship. The technology, method and equipment known to those of ordinary skill in the relevant field may not be discussed in detail, but in appropriate cases, the technology, method and equipment should be considered as a part of the authorization specification. In all examples shown and discussed here, any specific value should be interpreted as being merely exemplary, rather than as a limitation. Therefore, other examples of exemplary embodiments may have different values. It should be noted that similar reference numerals and letters represent similar items in the following drawings, so that once a certain item is defined in an accompanying drawing, it does not need to be further discussed in subsequent drawings.

[0030] <Example 1>

[0031] As attached Figure 1 As shown, this embodiment discloses a method for preparing diamond containing nitrogen vacancy color centers, comprising the following steps:

[0032] Step 1: providing an initial single crystal diamond containing nitrogen.

[0033] Specifically, single crystal diamond produced by CVD method is selected for use, with a thickness of no more than 300 um and a nitrogen content of ≥50 ppm.

[0034] Step 2: irradiating the initial single crystal diamond to obtain a pretreated single crystal diamond containing vacancy defects.

[0035] Specifically, the irradiation process uses a high-energy electron beam with an energy of 8 to 10 Mev, preferably 10 Mev; the irradiation time is 11-33 hours. In actual operation, the irradiation time is extended as the thickness of the initial single crystal diamond increases. Experiments have found that when a single crystal diamond with a nitrogen content of 50 ppm and a thickness of 200 um is irradiated for 11 hours to obtain a pretreated single crystal diamond, the efficiency of generating nitrogen vacancy color centers therein is increased to more than 10% compared to an irradiation time of less than 11 hours.

[0036] During the irradiation treatment process, a copper container is used to place the initial single crystal diamond, and a water cooling component is arranged around the copper container to prevent the diamond temperature from being too high and reduce the formation of surface oxides.

[0037] Step 3: Perform a first cleaning on the pretreated single crystal diamond to obtain a pretreated single crystal diamond after the first cleaning, wherein the first cleaning is performed using acetone and isopropanol in sequence.

[0038] Specifically, acetone cleaning is used to remove impurities such as organic matter remaining on the surface of the pretreated single crystal diamond, and isopropyl alcohol is used to remove acetone remaining on the surface of the pretreated single crystal diamond; in an exemplary scheme, acetone is first used to clean for 10-15 minutes with an ultrasonic cleaning device, and then isopropyl alcohol is used to clean for 1-2 minutes with an ultrasonic cleaning device, and finally an air gun is used to blow dry to obtain the pretreated single crystal diamond.

[0039] Step 4: subjecting the pretreated single crystal diamond after the first cleaning to a high temperature annealing treatment to obtain a semi-finished single crystal diamond containing a large number of dense nitrogen vacancy color centers, wherein the high temperature annealing treatment is performed in a vacuum environment.

[0040] Specifically, the pressure of the vacuum environment mentioned in the previous paragraph of this example is <1*10 -3Pa; during high temperature annealing, the annealing temperature is 850°C-1100°C, preferably 850°C; in some preferred schemes, during high temperature annealing, the temperature rise rate does not exceed 10°C per minute, the temperature drop rate does not exceed 10°C per minute, and the temperature is kept for a certain time when it is heated to the set temperature, and then it is heated to the annealing temperature. The set temperature is based on 1 / 2 of the annealing temperature, and the upper and lower deviations do not exceed 50°C. For example, when the annealing temperature is 850°C, and in a high vacuum environment (pressure <2*10 -4 Pa), first heated from room temperature to a set temperature of about 400 ° C, then kept at this set temperature for 2 hours, then heated to 850 ° C and kept for 4 hours, and finally cooled to room temperature according to the cooling decline rate.

[0041] In the prior art, considering the graphitization and oxidation degree of the diamond surface during high-temperature annealing, the annealing temperature is required to be no more than 800°C. Compared with the existing annealing temperature, this scheme uses an annealing temperature of 850°C-1100°C, which can increase the nitrogen vacancy color center generation efficiency by 2-6 times.

[0042] Step 5: pickling the semi-finished single crystal diamond to obtain a pickled semi-finished single crystal diamond, wherein the pickling temperature of the pickling solution is 215° C.-225° C.

[0043] Specifically, in the aforementioned high-temperature annealing step, this solution uses a relatively high temperature to achieve the preparation of diamonds with high nitrogen vacancy color centers, and the impurities generated on the diamond surface also increase accordingly. To solve this problem, step five uses a higher pickling temperature to solve this problem, that is, the pickling temperature is 215°C-225°C, preferably 220°C, and the matching pickling solution is a mixture of HNO3, H2SO4 and HClO4 prepared in a ratio of 1:1:1. When pickling is specifically implemented, a condenser is set on the upper side of the mixed solution to allow the evaporated acid to reflux; the pickling solution reaches the pickling temperature and is maintained for 2 hours before the pickling is terminated.

[0044] In the prior art, the pickling temperature is generally not greater than 200° C. In this solution, the pickling effect is not good. However, the pickling method of this solution can ensure that the surface cleanliness of the semi-finished single crystal diamond reaches the target level.

[0045] Step 6: Clean the pickled semi-finished single crystal diamond for a second time to obtain a finished single crystal diamond, wherein the second cleaning is performed using deionized water, acetone and isopropanol in sequence, and then drying the semi-finished single crystal diamond after cleaning.

[0046] Specifically, deionized water is used to remove the acid solution remaining on the diamond surface after pickling, acetone cleaning is used to remove impurities such as organic matter remaining on the surface of the pre-treated single crystal diamond, and isopropanol is used to remove the acetone remaining on the surface of the pre-treated single crystal diamond; in an exemplary scheme, the semi-finished single crystal diamond is first soaked in deionized water, then cleaned with acetone using an ultrasonic cleaning device for 10-15 minutes, then cleaned with isopropanol using an ultrasonic cleaning device for 1-2 minutes, and finally dried with an air gun to obtain the finished single crystal diamond. The diamond sample obtained by this method was tested, and the obtained ODMR spectrum is shown in the attached figure. Figure 2 As shown, it can be found that its zero-field splitting half-width is about 20MHz, and the fluorescence intensity is increased by 3-4 times compared with the original sample.

[0047] <Example 2>

[0048] This embodiment introduces an acid cleaning device, which is mainly used in the case of non-batch sample preparation, and the staff can manually operate to realize the acid cleaning of diamonds containing nitrogen vacancy color centers. Figure 3 , its structure mainly includes: bracket 1, condenser 2, cooling water pipe 3, water pump 4, water pool 5, pickling bottle 6 and heating box 7. When in use, condenser 2 can be installed on bracket 1 in a lifting manner, water pump 4 is installed in water pool 5 filled with cooling water, cooling water pipe 3 is divided into upper and lower pipes, through connection with condenser 2 and water pump 4, cooling water enters from the bottom of condenser 2, flows out from the top and flows back into water pool 5, the top of pickling bottle 6 is connected to the steam inlet of condenser 2, heating box 7 is located at the lower side of pickling bottle 6, and the pickling bottle 6 can be controlled by bracket 1 to enter heating box 7 for heating and temperature rise. The pickling device in this embodiment can be applied to the pickling process in step five of embodiment 1. When working, the semi-finished single crystal diamond is placed in the pickling bottle 6 filled with acid solution for pickling.

[0049] In a specific example, the bracket 1 is an iron stand, the condenser 2 is a serpentine condenser tube, the cooling water pipe 3 is a rubber tube, the water pump 4 has a head of 4m and a controllable water flow rate, the water tank 5 is an evaporating dish, the pickling bottle 6 is a 50ml single-mouth flask, and the heating box 7 is a controllable temperature electric heating jacket with a built-in thermocouple (temperature sensor) (designed for 50mL flasks). First, put the diamond into a 50mL single-mouth flask with tweezers, put the flask into a 50mL flask electric heating jacket, and connect the serpentine condenser tube. Then add 2mL of HNO3, H2SO4, and HClO4 respectively, start heating, set the temperature to 220℃, turn on the water pump (a micro water pump with a head of 4m) after the temperature stabilizes, and the condensed water flows from bottom to top along the condenser tube to condense the evaporated acid and reflux to avoid dry burning.

[0050] <Example 3>

[0051] This embodiment introduces a vacuum high temperature annealing device, which is mainly used in the preparation process of diamond containing nitrogen vacancy color center, see the attached Figure 4 The structure mainly includes: a quick-release vacuum flange 8, a tubular furnace 9, a vacuum three-way valve 10, a molecular pump group (not shown in the figure) and a special quartz container (not shown in the figure). The quick-release vacuum flange 8 and the vacuum three-way valve 10 are respectively connected to the two sides of the tubular furnace 9. The molecular pump group is connected to the vacuum three-way valve 10 through a pipeline. The special quartz container is used to place the diamonds to be processed. When in use, the special quartz container containing diamonds is pushed into the tubular furnace 9 through the quick-release vacuum flange 8; the vacuum three-way valve 10 is used to introduce nitrogen protective atmosphere and break the vacuum. The molecular pump group can achieve a vacuum of less than 1x10 -3 Pa vacuum environment.

[0052] During high temperature annealing, the temperature in the tube furnace 9 rises at a rate not exceeding 10°C per minute, and the temperature drops at a rate not exceeding 10°C per minute. The temperature rises from room temperature to 400°C and stays there for 2 hours, then rises to 850°C and stays there for 4 hours, and then cools to room temperature while controlling the cooling rate. The temperature change curve is shown in the attached figure. Figure 5 shown.

[0053] <Example 4>

[0054] This example introduces a diamond containing a nitrogen vacancy color center and its application. The diamond containing a nitrogen vacancy color center is prepared by the preparation method introduced in Example 1.

[0055] The diamond produced by the above method has a large number of NV color centers inside, few impurity defects and high surface cleanliness, making it very suitable for use as a sensor core for quantum precision measurement. Of course, it can also be used in the fields of quantum computing and quantum communication.

[0056] In the description of this specification, the description with reference to the terms "one embodiment", "example", "specific example", etc. means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representation of the above terms does not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described can be combined in any one or more embodiments or examples in a suitable manner.

[0057] The preferred embodiments of the present invention disclosed above are only used to help explain the present invention. The preferred embodiments do not describe all the details in detail, nor do they limit the invention to only specific implementation methods. Obviously, many modifications and changes can be made according to the content of this specification. This specification selects and specifically describes these embodiments in order to better explain the principles and practical applications of the present invention, so that those skilled in the art can understand and use the present invention well. The present invention is limited only by the claims and their full scope and equivalents.

Claims

1. A method for preparing diamond containing nitrogen vacancy color centers, characterized in that: The following steps are included: (1) providing an initial single crystal diamond containing nitrogen; (2) irradiating the initial single crystal diamond to obtain a pretreated single crystal diamond containing vacancy defects; (3) performing a first cleaning on the pretreated single crystal diamond to obtain a pretreated single crystal diamond after the first cleaning, wherein the first cleaning is performed by sequentially using acetone and isopropanol; (4) subjecting the pretreated single crystal diamond after the first cleaning to a high temperature annealing treatment to obtain a semi-finished single crystal diamond with nitrogen vacancy color centers, wherein the high temperature annealing treatment is performed in a vacuum environment; (5) performing pickling treatment on the semi-finished single crystal diamond to obtain a pickled semi-finished single crystal diamond, wherein the pickling temperature of the pickling solution is 215° C.-225° C.; (6) The semi-finished single crystal diamond after the acid washing is cleaned for a second time to obtain a finished single crystal diamond, wherein the second cleaning is performed by successively using deionized water, acetone and isopropanol for cleaning, and then drying the semi-finished single crystal diamond after cleaning.

2. The preparation method according to claim 1, characterized in that The irradiation process uses a high-energy electron beam with an energy of 8 to 10 MeV and an irradiation time of 11 to 33 hours.

3. The preparation method according to claim 1 or 2, characterized in that: The irradiation treatment process uses a copper container to place the initial single crystal diamond, and a water cooling component is configured around the copper container.

4. The preparation method according to claim 1, characterized in that: The initial single crystal diamond is grown by chemical vapor deposition, has a thickness of ≤300um, and a nitrogen content of ≥50ppm.

5. The preparation method according to claim 1, characterized in that: During high temperature annealing treatment, the annealing temperature is 850°C-1100°C.

6. The preparation method according to claim 5, characterized in that: During high temperature annealing treatment, the temperature rise rate shall not exceed 10°C per minute, the temperature drop rate shall not exceed 10°C per minute, and the temperature shall stay at the set temperature for a certain time before being raised to the annealing temperature. The set temperature is based on 1 / 2 of the annealing temperature, and the upper and lower deviations shall not exceed 50°C.

7. The preparation method according to claim 1, characterized in that: In the pickling treatment step, the pickling temperature of the pickling solution is 220° C., and the pickling solution is a mixed solution of HNO 3 , H 2 SO 4 and HClO 4 prepared in a ratio of 1:1:

1.

8. The preparation method according to claim 1, characterized in that: During high temperature annealing, the pressure of the vacuum environment is less than 1*10 -3 Pa.

9. A diamond containing a nitrogen vacancy color center, characterized in that: It is prepared by the preparation method according to any one of claims 1 to 8.

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