Nanoscale positioning preparation method of diamond NV color center

Abstract

The invention provides a preparation method of a diamond NV color center. The preparation method comprises the following steps: preparing one or more slotted nano structures on the surface of diamond; placing the diamond with the slotted nano-structure in a nitrogen source solution without metal elements, and performing pulse laser induced nitrogen injection by aligning laser to the area where the slotted nano-structure is located; and carrying out annealing treatment on the diamond subjected to pulse laser induced nitrogen injection to obtain the diamond with the NV color center. Nitrogen element shallow layer injection and nanoscale positioning in NV color center preparation are achieved at the same time.

Description

Technical Field

[0001] The present invention relates to the technical field of quantum materials, and particularly to a method for nano-scale positioning and preparation of diamond NV color centers assisted by grooved nanostructures. Background Art

[0002] The diamond nitrogen vacancy color center (NV color center for short) is a nano-scale crystal defect inside diamond, which has the advantages of stable physical properties, stable luminescence, and easy manipulation of electron spin at room temperature. And due to the unique electronic energy level structure of the NV color center, the NV color center has the ability to precisely sense and detect physical quantities such as external magnetic fields, electric fields, temperature, and stress, and shows excellent performance in detection accuracy and anti-interference ability.

[0003] Currently, the main methods for preparing diamond NV color centers generally include chemical vapor deposition, ion implantation, high-energy electron irradiation, laser direct writing, etc. Due to the limitations of the preparation environment and process, chemical vapor deposition is mainly used for doping specific layers of diamond and cannot position and quantitatively prepare NV color centers. Ion implantation usually needs to be combined with high-precision lithography technology, resulting in increased preparation difficulty and complex processes. High-energy electron irradiation requires that diamond itself contains a large amount of nitrogen elements or there is a high-concentration nitrogen-doped layer, and it is difficult to control the implantation amount to achieve the implantation of a single color center. The laser direct writing method is limited by the ammonia concentration of diamond itself and the diffusion of vacancies, resulting in limited positioning accuracy and concentration.

[0004] Therefore, a solution is required to precisely position and prepare NV color centers in high-purity diamond samples. Summary of the Invention

[0005] According to the current research status, in order to solve or at least partially solve the technical problems of the positioning and preparation of NV color centers in related technologies, the present invention proposes a method for nano-scale positioning and preparation of diamond NV color centers assisted by grooved nanostructures.

[0006] One object of the present invention is to achieve shallow implantation of nitrogen elements and nano-scale positioning in the preparation of NV color centers.

[0007] A further object of the present invention is to achieve controllable depth of nitrogen element implantation and controllable planar positioning accuracy.

[0008] In particular, the present invention provides a method for preparing diamond NV color centers, including:

[0009] Preparing one or more grooved nanostructures on the surface of diamond;

[0010] Place the diamond with the slotted nanostructure in a nitrogen source solution without metal elements, and use a laser to align the area where the slotted nanostructure is located for pulsed laser-induced nitrogen element implantation; and

[0011] Anneal the diamond after pulsed laser-induced nitrogen element implantation to obtain a diamond with NV color centers.

[0012] Optionally, each of the slotted nanostructures includes a pedestal of a first shape protruding from the surface of the diamond, and an upwardly open groove of a second shape formed within the pedestal.

[0013] Optionally, the height by which the pedestal protrudes from the surface of the diamond is 20 - 500 nm.

[0014] Optionally, the first shape is circular, and the radius of the circle is 50 - 1000 nm; or, the first shape is rectangular, and the side lengths of the rectangle are within the range of 50 - 1000 nm;

[0015] The second shape is circular, and the radius of the circle is 5 - 150 nm; or, the second shape is rectangular, and the length of the rectangle is 5 - 300 nm, and the width is 5 - 300 nm.

[0016] Optionally, preparing one or more slotted nanostructures on the surface of the diamond includes:

[0017] Coat a photoresist on the surface of the diamond, and perform electron beam lithography on the photoresist according to a pre-designed pattern to form a photoresist nanostructure;

[0018] Perform ion etching on the surface of the diamond with the photoresist nanostructure to obtain the one or more slotted nanostructures formed on the surface of the diamond.

[0019] Optionally, preparing one or more slotted nanostructures on the surface of the diamond includes:

[0020] Deposit a hard mask layer on the surface of the diamond;

[0021] Coat a photoresist on the hard mask layer, and perform electron beam lithography on the photoresist according to a pre-designed pattern to form a photoresist nanostructure;

[0022] Use the photoresist nanostructure to perform reactive ion etching on the hard mask layer and remove the photoresist to obtain a hard mask nanostructure;

[0023] Perform ion etching on the surface of the diamond with the hard mask nanostructure to obtain the one or more slotted nanostructures formed on the surface of the diamond.

[0024] Optionally, the nitrogen source solution is one selected from nitric acid solution, liquid nitrogen, ammonia water, and ammonium nitrate solution.

[0025] Optionally, the laser is a nanosecond or femtosecond laser with a wavelength of 400 - 850 nm.

[0026] Optionally, the annealing pressure for the annealing treatment is 5e - 5 Pa, the annealing temperature is 800 - 1000 °C, and the treatment time is 1 - 6 h.

[0027] Optionally, the annealing treatment is a staged annealing treatment, including:

[0028] Heating stage: Heating to 600 - 700 °C at a rate of 10 - 20 °C / min and maintaining at 600 - 700 °C for 1 - 2 h;

[0029] Insulation stage: Heating to 800 - 1000 °C at a rate of 5 - 10 °C / min and maintaining at 800 - 1000 °C for 1 - 6 h;

[0030] Cooling stage: Cooling to room temperature at a rate of 10 - 20 °C / min.

[0031] The method for preparing a diamond NV color center provided by the present invention first prepares one or more grooved nanostructures on the diamond surface, and then uses the grooved nanostructures to perform pulsed laser-induced nitrogen doping through a laser, simultaneously realizing nitrogen element injection and nanoscale positioning. Finally, through annealing treatment, the vacancies in the shallow layer of the diamond surface are combined with the nitrogen elements induced by the laser to form NV color centers. The grooved nanostructures in this technical solution are based on the Anapole effect, and can provide an enhancement of the electric field strength by 1 - 3 orders of magnitude in the grooved area. When a nanosecond / femtosecond laser irradiates the overall nanostructure area, the laser intensity in the grooved area will be enhanced by 1 - 3 orders of magnitude. By adjusting the laser intensity, selective laser induction in the grooved area is achieved, and the positioning injection of nitrogen elements is realized.

[0032] In applications, this grooved area can be accessed by NV color centers, thereby increasing the single-photon emission intensity and further improving the signal-to-noise ratio of the NV test experimental system.

[0033] Furthermore, by controlling the sizes of the base and grooves of the grooved nanostructures, the controllability of the depth of nitrogen element injection and the controllability of the planar positioning accuracy can be achieved.

[0034] The above description is only an overview of the technical solution of the present invention. In order to be able to understand the technical means of the present invention more clearly, it can be implemented in accordance with the content of the description. And in order to make the above and other purposes, features, and advantages of the present invention more obvious and understandable, the following specifically illustrates the specific embodiments of the present invention.

[0035] Those skilled in the art will better understand the above and other objects, advantages, and features of the present invention from the following detailed description of specific embodiments of the present invention in conjunction with the accompanying drawings. Description of the Drawings

[0036] By reading the following detailed description of the preferred embodiments, various other advantages and benefits will become clear to those of ordinary skill in the art. The drawings are only for the purpose of showing the preferred embodiments and are not considered to be a limitation of the present invention. Moreover, throughout the drawings, the same reference numerals are used to represent the same components. In the drawings:

[0037] Figure 1 is a schematic flow chart of a method for preparing a diamond NV color center according to an embodiment of the present invention;

[0038] Figure 2 is a schematic flow chart of a method for preparing a diamond NV color center according to another embodiment of the present invention;

[0039] Figure 3 is a schematic diagram of a grooved nanostructure on the surface of a diamond according to an embodiment of the present invention;

[0040] Figure 4 is a schematic design diagram of a grooved nanostructure according to an embodiment of the present invention;

[0041] Figure 5 is a schematic micro-nano processing flow chart of the steps for preparing a grooved nanostructure on the surface of a diamond according to an embodiment of the present invention;

[0042] Figure 6 is a schematic diagram of pulse laser-induced nitrogen element implantation according to an embodiment of the present invention;

[0043] Figure 7 is an electron microscope image of a grooved nanostructure prepared on the surface of a diamond according to an embodiment of the present invention;

[0044] Figure 8 is an electron microscope image of another grooved nanostructure prepared on the surface of a diamond according to another embodiment of the present invention;

[0045] Figures 9a to 9c is a simulation electric field enhancement intensity and electric field distribution diagram of a grooved nanostructure prepared on the surface of a diamond according to an embodiment of the present invention;

[0046] Figure 10 is Figures 9a to 9c a graph showing the variation trend of the electric field intensity enhancement curve at the center of the grooved area of the shown grooved nanostructure with wavelength. Detailed Embodiments

[0047] Exemplary embodiments of the present disclosure will be described in more detail below with reference to the accompanying drawings. Although the exemplary embodiments of the present disclosure are shown in the drawings, it should be understood that the present disclosure can be implemented in various forms and should not be limited by the embodiments set forth herein. On the contrary, these embodiments are provided so that the present disclosure can be more thoroughly understood and the scope of the present disclosure can be completely conveyed to those skilled in the art.

[0048] According to the current research status, in order to solve the problems of the positioning and preparation technology of NV centers in related technologies, the present invention proposes a method for nano-scale positioning and preparation of NV centers in a grooved nanostructure 200-assisted laser-induced diamond (especially high-purity diamond).

[0049] Figure 1 A schematic flowchart of a method for preparing a diamond NV center according to an embodiment of the present invention is shown. Refer to Figure 1 As shown, the preparation method may at least include the following steps S102 to step S106.

[0050] Step S102: Prepare one or more grooved nanostructures 200 on the surface of the diamond;

[0051] Step S104: Place the diamond with the grooved nanostructure 200 in a nitrogen source solution without metal elements, and use a laser to align the area where the grooved nanostructure 200 is located for pulsed laser-induced nitrogen element injection;

[0052] Step S106: Anneal the diamond after pulsed laser-induced nitrogen element injection to obtain a diamond with NV centers.

[0053] The generation of NV centers can be confirmed using a fluorescence confocal microscope.

[0054] In this embodiment, first, one or more grooved nanostructures 200 are prepared on the surface of the diamond, and then the grooved nanostructure 200 is used to perform pulsed laser-induced nitrogen doping through a laser, simultaneously achieving nitrogen element injection and nano-scale positioning. Finally, through annealing treatment, the vacancies in the shallow layer of the diamond surface are combined with the laser-induced injected nitrogen elements to form NV centers. The grooved nanostructure 200 in this technical solution is based on the Anapole effect and can provide an electric field strength enhancement of 1-3 orders of magnitude in the grooved area. When a nanosecond / femtosecond laser irradiates the overall nanostructure area, the laser intensity in the grooved area will increase by 1-3 orders of magnitude. By adjusting the laser intensity, selective laser induction in the grooved area is achieved, and the positioning injection of nitrogen elements is realized.

[0055] In an application, the grooved region can be accessed by NV color centers, thereby increasing the single-photon emission intensity and further improving the signal-to-noise ratio of the NV test experimental system. The grooved nanostructure 200 can also further enhance the NV fluorescence signal collected by a confocal microscope.

[0056] The number of the grooved nanostructures 200 is one or more. The multiple grooved nanostructures 200 can be arranged according to the actual application requirements of the NV color centers. For example, they can be arranged in an array form.

[0057] Figure 3 FIG. is a schematic diagram of the grooved nanostructure 200 on the diamond surface according to an embodiment of the present invention. Figure 4 FIG. is a design schematic diagram of the grooved nanostructure 200 according to an embodiment of the present invention. Refer to Figure 3 As shown, in some embodiments, each grooved nanostructure 200 may include a pedestal 210 of a first shape protruding from the surface of the diamond, and an upwardly opening groove 220 of a second shape formed within the pedestal 210.

[0058] The first shape of the pedestal 210 can be various regular or irregular shapes. For example, it can be circular, rectangular, triangular, etc.

[0059] The second shape of the groove 220 can be various regular or irregular shapes. For example, it can be circular, rectangular, triangular, etc.

[0060] The first shape of the pedestal 210 and the second shape of the groove 220 can be the same or different.

[0061] In some alternative embodiments, as Figure 4 shown, the height H by which the pedestal 210 protrudes from the surface of the diamond can be set to any value within the range of 20 to 500 nm. For example, 50, 80, 100, 150, 200, 250, 300, 350, 400, 450, 500 nm.

[0062] In some preferred embodiments, the first shape of the pedestal 210 can be circular. The radius of the circle of the pedestal 210 can be any value within the range of 50 to 1000 nm. For example, 50, 100, 150, 200, 250, 300, 350, 400, 450, 500, 600, 700, 800, 900, 1000 nm.

[0063] In some other preferred embodiments, the first shape of the base 210 may be rectangular. The side lengths of the rectangle of the base 210 may be any value within 50 to 1000 nm, such as 50, 100, 150, 200, 250, 300, 350, 400, 450, 500, 600, 700, 800, 900, 1000 nm. The length and width of the rectangle may not be equal or may be equal. When the length and width are equal, the rectangle is a square.

[0064] In some preferred embodiments, the second shape of the groove 220 may be circular. The radius of the circle of the groove 220 may be any value within the range of 5 to 150 nm, such as 10, 20, 30, 40, 50, 60, 70, 80, 90, 100, 110, 120, 130, 140, 150 nm.

[0065] In some other preferred embodiments, as Figure 4 shown, the second shape of the groove 220 may be rectangular. The length L of the rectangle of the groove 220 may be any value within the range of 5 to 300 nm, such as 10, 20, 30, 40, 50, 60, 70, 80, 90, 100, 110, 120, 130, 140, 150, 160, 170, 180, 190, 200, 210, 220, 230, 240, 250, 260, 270, 280, 290, 300 nm. The width W of the rectangle of the groove 220 may also be any value within the range of 5 to 300 nm, such as 10, 20, 30, 40, 50, 60, 70, 80, 90, 100, 110, 120, 130, 140, 150, 160, 170, 180, 190, 200, 210, 220, 230, 240, 250, 260, 270, 280, 290, 300 nm. The length and width of the rectangle may not be equal or may be equal. When the length and width are equal, the rectangle is a square.

[0066] In the embodiments of the present invention, by controlling the dimensions of the base 210 and the groove 220 of the grooved nanostructure 200, the depth control of nitrogen element implantation and the planar positioning accuracy control can be achieved.

[0067] In particular, the method of the present invention realizes the implantation of nitrogen elements on the surface of high-purity diamond with a grooved nanostructure 200 to achieve shallow nitrogen doping, with a controllable depth of 5 - 50 nm, and the positioning accuracy of the implanted nitrogen elements is determined by the size and processing conditions of the grooved nanostructure 200, and the planar positioning accuracy is controllable within 5 - 200 nm.

[0068] Figure 2 It is a schematic flow chart of a method for preparing a diamond NV color center according to another embodiment of the present invention.

[0069] See Figure 2 , in some embodiments, step S102 may specifically include:

[0070] Step S1021, perform electron beam lithography on the surface of the diamond to obtain a photoresist nanostructure.

[0071] Specifically, coat a photoresist on the surface of the diamond, and perform electron beam lithography on the photoresist according to a pre-designed pattern to form a photoresist nanostructure, so that the surface of the diamond is provided with the photoresist nanostructure. The pre-designed pattern corresponds to the pattern of the slotted nanostructure 200.

[0072] The photoresist can be a positive electron beam lithography resist, such as PMMA, AR-P6200, ZEP520, etc., or a negative electron beam lithography resist, such as HSQ, AR-N7520, etc. The specific type used is determined according to the size of the designed nanostructure.

[0073] Those skilled in the art should know that electron beam lithography includes the processes of exposure and development, and the specific operation parameters can be selected according to the photoresist used in the specific process.

[0074] After the photoresist coating (i.e., spin coating process) is completed, conductive treatment can also be performed. Specifically, the same spin coating method can be used, and a commercial conductive photoresist can be used to complete the conductive treatment.

[0075] Step S1022, perform ion etching on the surface of the diamond to obtain one or more slotted nanostructures 200 on the surface of the diamond.

[0076] The ion etching method used in this step may include inductively coupled plasma reactive ion etching, reactive ion etching, ion beam etching, focused ion beam etching, etc. The gas used for etching can be oxygen, argon, chlorine, sulfur hexafluoride, etc. The operation parameters of the etching can be set according to the specific etching method used and the size design of the nanostructure.

[0077] In a specific embodiment, taking inductively coupled plasma reactive ion etching as an example, the etching gases used are oxygen and argon, and the specific etching parameter selection and etching time are determined according to the specific nanostructure parameters.

[0078] In some other embodiments, step S102 may specifically include:

[0079] Step S1021’, perform electron beam lithography on the surface of the diamond to obtain a hard mask nanostructure.

[0080] Specifically, first, a hard mask layer is deposited on the surface of the diamond. The hard mask layer can be made of metallic materials such as titanium, aluminum, chromium, etc.; or non-metallic materials such as silicon dioxide, silicon, silicon nitride, etc. The deposition methods include electron beam evaporation, thermal evaporation, magnetron sputtering, plasma enhanced chemical vapor deposition (PECVD), etc.

[0081] Then, a photoresist is coated on the hard mask layer, and electron beam lithography is performed on the photoresist according to a pre-designed pattern to form a photoresist nanostructure. The formation process of the photoresist nanostructure is as described above and will not be repeated.

[0082] Finally, the hard mask layer is subjected to reactive ion etching using the photoresist nanostructure and the photoresist is removed to obtain a hard mask nanostructure, so that the surface of the diamond has a hard mask nanostructure. The etching of such a hard mask layer and the removal of the photoresist should be well-known to those skilled in the art and will not be elaborated here.

[0083] Step S1022, ion etching is performed on the surface of the diamond to obtain one or more grooved nanostructures 200 on the diamond surface.

[0084] In some alternative embodiments, while preparing the grooved nanostructures 200, markers for positioning are prepared on the surface of the diamond, such as Figure 5 the markers located at the four corners of the diamond surface as shown in step (d) of

[0085] In step S104, a single nitrogen source is provided by a nitrogen source solution without metal elements for nitrogen implantation, without introducing other metal impurities.

[0086] In some embodiments, the nitrogen source solution can be one selected from nitric acid solution, liquid nitrogen, ammonia water, ammonium nitrate solution, etc.

[0087] In a specific embodiment, the nitrogen source solution is 65% concentrated nitric acid.

[0088] In some embodiments, the laser selected in step S104 is a nanosecond or femtosecond laser, and the wavelength can be 400 - 850 nm, such as 515 nm, 800 nm.

[0089] The wavelength and parameters of the laser (such as laser energy) can be set according to the actually required nitrogen doping concentration through simulation and referring to the simulation results. The relevant simulation methods have been disclosed in existing literature and will not be elaborated here.

[0090] In a specific embodiment, the propagation direction of the laser can be changed by a mirror and a lens group. The laser is aligned and focused onto the slotted nanostructure 200 region on the surface of a diamond immersed in a nitrogen-containing solution (such as concentrated nitric acid solution) by using an objective lens, and single / multi-pulse induction is performed. The three-dimensional movement of the diamond sample is controlled by a three-dimensional displacement platform. A high-purity diamond with a clearly designed slotted nanostructure 200 is immersed in a Teflon petri dish containing 65% concentrated nitric acid. The laser is focused onto the region where the slotted nanostructure 200 is located by using an objective lens, and the region of the diamond with the slotted nanostructure 200 is processed by using pulsed laser. The selection of the laser wavelength and parameters can refer to the simulation results. After processing, it is ultrasonically treated with deionized water, acetone, and isopropyl alcohol. After completion, the induction situation is confirmed by using a microscope and an electron microscope, and it is dried and waiting for the next step of treatment.

[0091] In some embodiments, the annealing pressure in step S106 is 5e-5 Pa, the annealing temperature is 800 - 1000 °C, and the treatment time is 1 - 6 h.

[0092] The annealing method can adopt rapid annealing, laser annealing, etc.

[0093] In some embodiments, the annealing treatment can adopt staged annealing treatment, specifically including:

[0094] Heating stage: Heating at a rate of 10 - 20 °C / min to 600 - 700 °C and maintaining at 600 - 700 °C for 1 - 2 h;

[0095] Insulation stage: Heating at a rate of 5 - 10 °C / min to 800 - 1000 °C and maintaining at 800 - 1000 °C for 1 - 6 h;

[0096] Cooling stage: Cooling at a rate of 10 - 20 °C / min to room temperature.

[0097] In a specific embodiment, the staged annealing treatment includes:

[0098] Heating stage: Heating at a rate of 10 °C / min to 700 °C and maintaining at 700 °C for 1 - 2 h;

[0099] Insulation stage: Heating at a rate of 6 °C / min to 800 - 1000 °C and maintaining at 800 - 1000 °C for 1 - 6 h;

[0100] Cooling stage: Cooling at a rate of 10 °C / min to room temperature.

[0101] After annealing is completed, the diamond can also be subjected to pickling post-treatment. Specifically, the diamond is heated and acid-boiled (at 150-200 °C) using a mixture of concentrated sulfuric acid and concentrated nitric acid (volume ratio 3:1), and then cleaned with deionized water and dried. The mass fraction of the concentrated sulfuric acid used is 98%, and the mass fraction of the concentrated nitric acid is 65%.

[0102] See Figure 2 , in some embodiments, before step S102, the preparation method may further include:

[0103] Step S100, performing surface pretreatment on the surface of the diamond.

[0104] Specifically, the surface pretreatment includes physical and chemical pretreatment. First, perform physical mechanical polishing on the surface of the diamond, and the roughness requirement of the polished diamond surface is R < 2 nm. After polishing, use a mixture of concentrated sulfuric acid and concentrated nitric acid (volume ratio 3:1) for heating and acid-boiling (at 150-200 °C) to remove impurities (including any metal impurities and organic substances) on the surface of the diamond. The mass fraction of the concentrated sulfuric acid used is 98%, and the mass fraction of the concentrated nitric acid is 65%.

[0105] Continue to refer to Figure 2 , in some embodiments, after completing the ion etching of the diamond surface to prepare one or more grooved nanostructures 200, the preparation method may further include:

[0106] Step S103, performing pickling post-treatment on the etched diamond to obtain a diamond nanostructure with clear and stable patterns.

[0107] Specifically, the diamond can be heated and acid-boiled (at 150-200 °C) using a mixture of concentrated sulfuric acid and concentrated nitric acid (volume ratio 3:1).

[0108] Figure 5 is a schematic diagram of the micro-nano processing flow of the steps for preparing the grooved nanostructure 200 on the surface of the diamond according to an embodiment of the present invention. The following is combined with Figure 5 , and through specific embodiments, the steps for preparing the grooved nanostructure 200 on the surface of the diamond in the preparation method of the present invention are specifically described.

[0109] Figure 5 Step (a) shows the electron beam lithography pretreatment of high-purity diamond, that is, performing surface pretreatment on the surface of the diamond.

[0110] Figure 5Steps (b) and (c) exemplarily show the process of constructing the designed photoresist and hard mask nanopatterns on the diamond surface by electron beam lithography. The specific detailed operations are as follows: First, the diamond is ultrasonically treated with deionized water, acetone, and isopropyl alcohol for 5 - 10 minutes respectively. After drying with a nitrogen gun, the whole diamond is placed in a spin coater for the first spin coating process. The selected photoresist includes electron beam positive photoresist (such as PMMA, AR-P6200, ZEP520, etc.) or electron beam negative photoresist (such as HSQ, AR-N7520, etc.). The specific type used is determined by the size of the designed nanostructure, and the specific process parameters are carried out according to the instructions of the selected photoresist. After spin coating, conductive treatment is performed. Using the same spin coating method, a commercial conductive photoresist is used to complete the conductive treatment. The exposure operation is completed using an electron beam lithography machine. The selected parameters are based on the photoresist used in the specific process, and the pattern is designed according to the design requirements. After the corresponding development operation, a diamond surface with photoresist nanostructures is obtained. If a diamond surface with hard mask nanostructures needs to be prepared, after ultrasonic treatment with deionized water, acetone, and isopropyl alcohol, the diamond is boiled in piranha solution to remove all organic substances. After washing with deionized water and drying, a hard mask is deposited using methods such as electron beam evaporation, thermal evaporation, magnetron sputtering, PECVD, etc. The metal types include metals such as titanium, aluminum, chromium, etc., and non-metals include silicon dioxide, silicon, silicon nitride, etc. Subsequently, spin coating, exposure, and development operations are carried out according to the method described above to obtain a diamond surface with photoresist nanostructures. After reactive ion etching and photoresist removal treatment, a diamond surface with hard mask nanostructures is obtained.

[0111] Figure 5Step (d) shows the ion etching of the high-purity diamond surface with a photoresist nanostructure or a hard mask nanostructure. The etching methods used include inductively coupled plasma reactive ion etching, reactive ion etching, ion beam etching, etc. The gases used for etching are oxygen, argon, chlorine, sulfur hexafluoride, etc. After the etching is completed, an acid pickling treatment is carried out. The method used is to heat and boil the mixture of concentrated sulfuric acid and concentrated nitric acid (volume ratio 3:1) at 150-200 °C to obtain high-purity diamond with the designed nanostructure. Taking inductively coupled plasma reactive ion etching as an example, first, the obtained high-purity diamond with the designed photoresist or hard mask nanostructure is adhered to a four-inch silicon wafer carrier using thermal conductive silicone grease. The etching gas used is oxygen. The specific etching parameters are selected as follows: oxygen flow rate: 30 sccm, ICP power 650 W, RF power 150 W, chamber pressure 5 mtorr, and the etching rate is about 120 nm / min. The etching time is determined according to the specific structural parameters. If a focused ion beam etching is used to form the pattern of the slotted area, the system used is a Ga / Ne / He focused ion beam etching system. Taking Ga focused ion beam etching as an example, the Ga ion beam processing parameters used are 30 kV and 7.7 pA, and the processing depth is selected as 100 nm.

[0112] Figure 6 Schematic diagram of pulsed laser-induced nitrogen element implantation according to an embodiment of the present invention. In a specific embodiment, as Figure 6 shown, an objective lens is used to focus a nanosecond or femtosecond laser onto the nanostructure marker area of the diamond sample, and the three-dimensional movement of the diamond sample is controlled by a three-dimensional displacement platform. The high-purity diamond with the clearly designed and stable nanostructure is immersed in a petri dish with 65% concentrated nitric acid. An objective lens is used to focus the laser onto the area where the nanostructure marker is located, and the pulsed laser is used to process the area of the diamond with the nanostructure. Under the enhancement condition of the nanostructure, the laser energy in the slotted area of the nanostructure is 1-3 orders of magnitude higher than that in the surrounding area. By controlling the laser intensity, a local plasma is formed in the slotted area of the nanostructure, and the nitrogen element in the nitric acid solution is doped into the shallow surface of the diamond using the laser energy. After the processing is completed, ultrasonic treatment is carried out using deionized water, acetone, and isopropyl alcohol. After completion, a microscope and an electron microscope EDS analysis are used to confirm the laser-induced doping situation. After drying, it waits for the next step of processing.

[0113] Figure 7 and Figure 8 respectively show the electron microscope images of two kinds of slotted nanostructures 200 prepared on the surface of the diamond according to the preparation method of the present invention. From Figure 7 and Figure 8It can be seen that the fabricated slotted nanostructure 200 is a nanostructure with rectangular slots. The length of the slotted area is approximately 200 nm, the width is approximately 20 - 25 nm, and the overall height is approximately 70 and 80 nm respectively. This indicates that the surface processing method of the slotted nanostructure 200 of the present invention has feasibility and size controllability.

[0114] Figures 9a to 9c It is the simulated electric field enhancement intensity and electric field distribution diagram of the slotted nanostructure 200 fabricated on the surface of diamond according to an embodiment of the present invention; Figure 10 For Figures 9a to 9c It is the graph showing the variation trend of the electric field intensity enhancement curve at the center of the slotted area of the shown slotted nanostructure 200 with wavelength.

[0115] In this embodiment, the simulation method adopted is finite element simulation, and COMSOL Multiphysics is used for the simulation process to design the shape and size parameters of the nanostructure. The general conditions for the simulation are set as follows: the nanostructure is a rectangular slit disk, the thickness H of the disk is 80 nm, the diameter D is 480 nm, the size of the slotted rectangle is L = 162 nm, and W = 20 nm. In the background field setting, a plane wave polarized along the y - axis direction is incident on the entire disk structure along the z - axis direction, and the scanning wavelength range is between 330 nm and 850 nm. The background medium is air with a refractive index n = 1, the material is selected as single - crystal diamond, and the refractive index data is from the article "Single - crystal CVD film" by Taylor et al. (Taylor et al. 2023: Single - crystal CVD film). A Perfect Matched Layer (PML) is added on the boundary of the simulation model. A perfect electric conductor is added, the simulation mesh is selected as 50 nm, and the overall electric field distribution and the electric field enhancement intensity distributions in the YZ and XZ directions are obtained as Figures 9a to 9c shown, and the variation trend of the electric field intensity enhancement curve at the center of the slotted area with wavelength λ0 is as Figure 10 shown. From Figures 9a to 9c and Figure 10 the simulation results show that the electric field enhancement in the slotted area reaches nearly two orders of magnitude. According to the limitations of the processing conditions, through further parameter optimization, the electric field enhancement in the slotted area can be further improved.

[0116] In the specification provided herein, a large number of specific details are described. However, it can be understood that the embodiments of the present invention can be practiced without these specific details. In some instances, well - known methods, structures, and technologies are not shown in detail so as not to obscure the understanding of this specification.

[0117] At this point, those skilled in the art should recognize that although many exemplary embodiments of the present invention have been shown and described in detail herein, many other variations or modifications that conform to the principles of the present invention can still be directly determined or derived from the disclosed content of the present invention without departing from the spirit and scope of the present invention. Therefore, the scope of the present invention should be understood and determined to cover all such other variations or modifications.

Claims

1. A method for preparing a diamond NV color center, comprising: Preparing one or more grooved nanostructures on the surface of a diamond; Placing the diamond with the grooved nanostructures in a nitrogen source solution without metal elements, and using a laser to align the area where the grooved nanostructures are located for pulsed laser-induced nitrogen element implantation; and Annealing the diamond after pulsed laser-induced nitrogen element implantation to obtain a diamond with NV color centers.

2. The method for preparing a diamond NV color center according to claim 1, wherein, Each of the grooved nanostructures includes a base of a first shape protruding from the surface of the diamond, and an upward-opening groove of a second shape formed within the base.

3. The method for preparing a diamond NV color center according to claim 2, wherein, The height by which the base protrudes from the surface of the diamond is 20 - 500 nm.

4. The method for preparing a diamond NV color center according to claim 2, wherein, The first shape is circular, and the radius of the circle is 50 - 1000 nm; alternatively, the first shape is rectangular, and each side length of the rectangle is in the range of 50 - 1000 nm; The second shape is circular, and the radius of the circle is 5 - 150 nm; alternatively, the second shape is rectangular, and the length of the rectangle is 5 - 300 nm, and the width is 5 - 300 nm.

5. The preparation method of the diamond NV color center according to any one of claims 1-4, wherein, The step of preparing one or more grooved nanostructures on the surface of the diamond includes: Coating a photoresist on the surface of the diamond, and performing electron beam lithography on the photoresist according to a pre-designed pattern to form a photoresist nanostructure; Performing ion etching on the surface of the diamond with the photoresist nanostructure to obtain the one or more grooved nanostructures formed on the surface of the diamond.

6. The method for preparing a diamond NV color center according to any one of claims 1-4, wherein, The step of preparing one or more grooved nanostructures on the surface of the diamond includes: Depositing a hard mask layer on the surface of the diamond; Coating a photoresist on the hard mask layer, and performing electron beam lithography on the photoresist according to a pre-designed pattern to form a photoresist nanostructure; Performing reactive ion etching on the hard mask layer using the photoresist nanostructure and removing the photoresist to obtain a hard mask nanostructure; Performing ion etching on the surface of the diamond with the hard mask nanostructure to obtain the one or more grooved nanostructures formed on the surface of the diamond.

7. The method for preparing a diamond NV color center according to any one of claims 1-4, wherein The nitrogen source solution is one selected from nitric acid solution, liquid nitrogen, ammonia water, and ammonium nitrate solution.

8. The preparation method of the diamond NV color center according to any one of claims 1-4, wherein, The laser is a nanosecond or femtosecond laser with a wavelength of 400 - 850 nm.

9. The preparation method of the diamond NV color center according to any one of claims 1-4, wherein, The annealing pressure for the annealing treatment is 5e-5 Pa, the annealing temperature is 800 - 1000 °C, and the treatment time is 1 - 6 h.

10. The method for preparing a diamond NV color center according to claim 9, wherein, The annealing treatment is a staged annealing treatment, including: Heating stage: Heating at a rate of 10 - 20 °C / min to 600 - 700 °C and maintaining at 600 - 700 °C for 1 - 2 h; Insulation stage: Heating at a rate of 5 - 10 °C / min to 800 - 1000 °C and maintaining at 800 - 1000 °C for 1 - 6 h; Cooling stage: Cooling at a rate of 10 - 20 °C / min to room temperature.

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