A method for fabricating diamond color center arrays based on phase-separated nanomasks

Abstract

This invention belongs to the field of micro / nano fabrication technology, specifically a method for preparing a diamond color center array based on a phase-separated nanomask. The invention includes two schemes: Scheme 1 includes: pretreatment of diamond raw material; deposition of a hard mask layer on the diamond surface; coating an adhesive layer; coating with a phase-separable patterned block copolymer or a polymeric material such as a biomolecule that can be assembled; annealing the diamond; selectively etching the surface film to form a nanomask; nitrogen ion implantation to form an NV color center array; removing the hard mask; and removing surface carbon impurities through vacuum high-temperature annealing and acid washing to obtain a high-quality color center array. Scheme 2 simplifies the hard mask deposition steps by directly coating a thick film of a phase-separable patterned polymeric material onto the diamond raw material surface. This invention achieves low-cost, high-mask precision and resolution, high-throughput scalability, and large-area nanomask ion implantation color center array preparation by employing two different process flows.

Description

Technical Field

[0001] This invention belongs to the field of micro-nano fabrication technology, specifically relating to a method for preparing a diamond color center array based on a phase-separated nanomask. Background Technology

[0002] Diamond NV centers are optically active point defects within diamond, formed when two adjacent carbon atoms are replaced by a nitrogen atom and a vacancy, subsequently trapping an electron. They can exist in two electronic states: the ground state and the excited state. Under certain conditions, they selectively absorb specific wavelengths while emitting fluorescent photons and are sensitive to external magnetic fields. In particular, they have significant application value in room-temperature quantum sensors, magnetic sensing, integrated optical quantum chips, and quantum information processing. High-precision magnetic field measurement based on NV centers still requires improvement; accurately measuring magnetic field vector strength at the microtesla level and magnetic field gradients at micrometer-level spacing remains challenging. Fabricating single NV center arrays with high uniformity, large area, and high sensitivity is crucial for high-precision detection of static magnetic field vectors and magnetic field gradients at extremely small spacings.

[0003] Currently, the main methods for fabricating diamond NV centers include chemical vapor deposition, thermal annealing, electron beam processing, ion implantation, and ultrafast laser irradiation. Ion beam implantation, compatible with semiconductor processes and suitable for large-area fabrication, is currently the most widely used method for NV center fabrication. In type IIa high-purity diamond, N-ion beams are implanted through a photolithographic mask, and NV centers are generated after annealing, achieving planar position control. However, relying on mask ion implantation, the depth of NV center formation exhibits a Gaussian distribution, making it difficult to control the amount of N-ion implanted, and thus challenging to control the formation of individual NV centers. To address these issues, it is necessary to develop a nanomask ion implantation color center array fabrication technology that simultaneously possesses low cost, high mask accuracy and resolution, high throughput scalability, and large-area or even wafer-level fabrication capabilities. Summary of the Invention

[0004] The purpose of this invention is to provide a method for fabricating a diamond color center array based on a polymer phase-separated nanomask, so as to achieve the fabrication of a nanomask ion implantation color center array with high mask accuracy and resolution, high throughput scalability, large area and even wafer-level fabrication area.

[0005] The present invention provides a method for preparing a diamond color center array based on a polymer phase-separated nanomask, comprising two schemes:

[0006] Option 1 involves obtaining a nanopore array pattern through polymer phase separation and assembly, transferring the nanopore array pattern to a hard mask layer on a diamond surface, and then using the nanopore array hard mask to prepare a color center array via ion implantation. The specific steps are as follows:

[0007] Step S1: Pre-treat the diamond surface to remove organic and inorganic impurities, providing a clean surface for subsequent processes, and obtain the pre-treated diamond surface.

[0008] Step S2: Prepare a hard mask layer on the pretreated diamond surface. The hard mask layer is made of silicon thin film, or oxide thin film or metal thin film; the film thickness is less than 200 nm.

[0009] Step S3: Apply an adhesive layer onto the hard mask layer to enhance the adhesion between the polymer material and the hard mask;

[0010] Step S4: Coat the adhesive layer with a phase-separable patterned polymer material to form nanoscale patterns using its self-assembly properties;

[0011] Step S5: Anneal the selected areas of the thin film formed in step S4 to induce and regulate the phase separation structure of the polymer material, form a uniform nanomask, and enhance the pattern clarity;

[0012] Step S6: Etch the sample after annealing phase separation and assembly, transfer the obtained pattern to the substrate, etch the hard mask layer (oxide film, metal film or silicon film) to obtain the nanomask layer of nanopore array;

[0013] Step S7: Under the protection of a nanomask, nitrogen ions are injected into diamond to form a regular array of NV color centers;

[0014] Step S8: Use wet acid washing or dry reactive ion etching to remove the hard mask and expose the diamond surface implantation area;

[0015] Step S9: Perform nitrogen ion implantation and high-temperature annealing in a vacuum environment to activate the color center and improve its optical properties;

[0016] Step S10: Post-process the diamond NV color center array to obtain a diamond NV color center array with a clear and stable pattern.

[0017] Furthermore:

[0018] In step S2, the silicon thin film in the hard mask layer is prepared by spin coating and has a thickness of 50-100 nm; the oxide thin film or metal thin film is prepared by semiconductor thin film deposition processes such as thermal evaporation, ALD, CVD or magnetron sputtering and has a thickness of 10-50 nm. The preferred materials are oxides such as silicon dioxide and titanium dioxide or metals such as aluminum.

[0019] In step S3, the adhesive layer material, for the block copolymer of the polymer material used, is selected as a molecular brush layer composed of two segments or a non-block homopolymer molecular felt layer, with a thickness of 10-20 nm.

[0020] In step S4, the phase-separable patterned polymer material can be a diblock copolymer such as PS-b-PMMA.

[0021] In step S5, the annealing can be performed in various ways, including laser annealing, overall thermal annealing, and solvent-induced phase separation annealing.

[0022] In step S7, the nitrogen ion implantation energy is 10-200 keV, and the implantation dose is 1×10⁻⁶. 12 -1×10 14 / cm 2 .

[0023] In step S8, the acid is selected from nitric acid, sulfuric acid, and perchloric acid, preferably a mixture of nitric acid, sulfuric acid, and perchloric acid, and more preferably the ratio of nitric acid / sulfuric acid / perchloric acid is 1:1:1.

[0024] In step S9, the high-temperature annealing temperature is 800-1100℃, and the time is 1-2 hours.

[0025] In this invention, the size and spacing of the color center array can be controlled by controlling the polymer phase separation and ion implantation conditions; the size range of the color center distribution points is 10nm-100nm; and the color center spacing ranges from 10nm to 100nm.

[0026] Option 2, the specific steps are as follows:

[0027] Step S1: Pre-treat the diamond surface to remove organic and inorganic impurities, and obtain the pre-treated diamond surface.

[0028] Step S2: Directly coat the pretreated diamond surface with a block copolymer polymer film that can be phase-separated and patterned with high Flory-Huggins interaction parameter values ​​(high χ value), or self-assembling biomacromolecules such as amyloid protein and DNA, to form nanoscale patterns. The film thickness is greater than 200 nm (as opposed to the film with a thickness of less than 200 nm in Scheme 1, it is called a thick film).

[0029] Step S3: Perform laser or solvent annealing on the block copolymer polymer film to improve the phase separation structure of the block copolymer polymer material; annealing is not required for the biomacromolecule film.

[0030] Step S4: Etch the assembled sample to obtain a nanomask layer with a nanopore array;

[0031] Step S5: Directly use the polymer thick film after phase separation, assembly, and selective etching as a mask to perform nitrogen ion implantation to form color centers;

[0032] Step S6: After nitrogen ion implantation, the polymer layer is removed by acid washing;

[0033] Step S7: Perform high-temperature annealing in a vacuum environment to activate the color centers;

[0034] Step S8: Acid-wash the diamond NV color center array to improve the quality of the color centers.

[0035] Furthermore:

[0036] In step S2, typical materials of the high χ value block copolymer polymer are PS-b-P2VP, PS-b-PDMS, etc., with a χ value greater than 0.07 and less than 0.1 at 150℃.

[0037] In step S3, the biomacromolecule material self-assembles to form nanopatterns, eliminating the need for annealing in step S4.

[0038] In this invention, the size and spacing of the color center array can be controlled by controlling the polymer phase separation and ion implantation conditions; the size range of the color center distribution points is 10nm-100nm; and the color center spacing ranges from 10nm to 100nm.

[0039] Compared with the prior art, the present invention has the following main technical effects:

[0040] (1) By using polymer phase separation technology to self-assemble nanomasks, color centers were successfully confined in nanopores, enabling stable, low-cost, and large-area fabrication of color center arrays over a wide range of regions.

[0041] (2) By precisely controlling the polymer phase separation and ion implantation conditions, the size and spacing of the color centers can be precisely controlled, simplifying the preparation process of the color center array and making it easy to operate. Attached Figure Description

[0042] Figure 1 This is a block diagram (Scheme 1) of the method for preparing diamond color center array based on polymer phase separation nanomask of the present invention.

[0043] Figure 2This is a flowchart (Scheme 1) of the method for preparing a diamond color center array based on a polymer phase-separated nanomask according to the present invention. In the flowchart, a is a schematic diagram of the diamond sample structure after pretreatment; b is a schematic diagram of the diamond sample structure with deposited silicon, oxide, or metal thin films; c is a schematic diagram of the diamond sample structure immediately following an adhesion layer; d is a schematic diagram of the diamond sample structure with a phase-separated polymer material layer spin-coated on the adhesion layer; e is a schematic diagram of the diamond sample structure after annealing to form phase separation; f is a schematic diagram of the diamond sample structure with pores formed after selective etching; g is a schematic diagram of the diamond sample structure after ion implantation; and h is a schematic diagram of the diamond sample structure after removing the hard mask.

[0044] Figure 3 These are diamond film samples deposited on silicon wafers using chemical vapor deposition. (a) shows a fully polished diamond sample, and (b) shows a partially polished diamond sample.

[0045] Figure 4 This is a confocal scanning imaging result of the diamond NV color center array in this invention.

[0046] In the figure, the numbers are as follows: 1 is the pretreated diamond, 2 is the Si film, oxide film or metal film, 3 is the adhesive layer, 4 is the phase-separated patterned polymer material layer, 5 is the implanted ions, and 6 is the formed color center. Detailed Implementation

[0047] The present invention will be further described below through examples.

[0048] Example 1: Scheme 1, see Figure 2 As shown, the specific steps are as follows:

[0049] Step S1: Pretreatment of diamond raw materials, see Figure 2 (a) Place the high-purity diamond sheet into a beaker containing isopropanol and use an ultrasonic cleaner to ultrasonically clean it for 30 minutes to remove organic contaminants from the surface.

[0050] Alternatively, diamond sheets can be acid-washed by immersing them in a mixed acid solution of HClO4 / HNO3 / H2SO4 (1:1:1) at room temperature for 10 minutes, and then rinsing with deionized water.

[0051] Step S2: Hard mask deposition, see Figure 2 (b) A silicon thin film with a thickness of 100 nm was deposited on the diamond surface using atomic layer deposition (ALD) technology to obtain a hard mask layer;

[0052] Step S3: Adhesive layer coating, see Figure 2(c) Apply an adhesive layer (either a molecular brush layer consisting of two segments of the block copolymer or a non-block homopolymer molecular felt layer) to the hard mask to enhance the adhesion between the polymer and the hard mask.

[0053] Step S4: Coating with a phase-separable patterned polymer material: See [link to step S4] Figure 2 (d) A phase-separable patterned polymer PS-b-PMMA diblock copolymer film is spin-coated onto the adhesive layer.

[0054] Step S5: Annealing treatment to induce polymer phase separation and assembly: See Figure 2 (e) The diamond sheet coated with polymer material is heat-treated to promote phase separation of the polymer material and assemble it into a nanoscale pattern.

[0055] Step S6: Selective Etching: See Figure 2 (f) Using a plasma etching machine to etch the silicon thin film, the nanopore array pattern is transferred to the hard mask layer.

[0056] Step S7: Nitrogen ion implantation: See Figure 2 (g) The diamond sheet is loaded into the ion implanter, and the energy and dose are controlled (a typical set of parameters is: energy 10 keV, implantation dose 4 × 10⁻⁶). 13 / cm 2 ), forming color centers in diamond.

[0057] Step S8: Remove the hard mask: See Figure 2 (h) The hard mask layer was removed at room temperature for 30 minutes using a mixed acid solution (HClO4 / HNO3 / H2SO4 (1:1:1)) and then rinsed with deionized water.

[0058] Step S9: Vacuum high-temperature annealing: Place the diamond sheet in a vacuum furnace and treat it in a vacuum environment at 850°C for 2 hours to activate the color centers and improve its optical properties.

[0059] Step S10: Acid washing to remove surface carbon impurities: Treat with a mixed acid solution at room temperature for 10 minutes to remove surface carbon impurities, then rinse with deionized water to obtain a high-quality color center array.

[0060] Example 2: Scheme Two

[0061] This embodiment provides the preparation of a color center array for ion implantation using a polymer phase-separated assembly nanomask. The preparation method is the same as in Example 1, except that steps S2, S3, S4 in Example 1 are replaced by directly coating a phase-separable patterned PS-b-PMMA diblock copolymer polymer film larger than 200 nm. At the same time, steps S6 and S8 in Example 1 are replaced by etching only the polymer layer and removing only the polymer layer. This thick film process can provide better mask protection and is suitable for more complex pattern transfer and deeper ion implantation.

[0062] Example 3: Adjusting Annealing Conditions

[0063] Based on Examples 1 and 2, the annealing temperature and time were varied to investigate the effect of annealing conditions on the self-assembly of phase-separated polymer materials. Specifically, laser annealing technology was employed, optimizing parameters such as laser power and laser scanning speed. For example, the laser wavelength was set to 532 nm or 980 nm. When the laser was a continuous-wave laser, the laser spot could be a Gaussian circular spot with a diameter of 10–50 μm, a laser power of 2–20 W, and a scanning speed of 10–1000 μm / s. When the laser was a nanosecond laser, the laser spot could also be a Gaussian circular spot with a diameter of 10–50 μm, a laser power of 100–500 mW, a scanning speed of 250–1000 nm / s, a laser pulse width of 100–200 ns, and a laser repetition frequency of 100–300 kHz. This improved the uniformity and repeatability of the nanopore array pattern, enabling micro / nano-scale localized selective annealing, controlling the shape of the annealed region, and thus controlling nano-assembly and patterning.

[0064] Example 4: Optimization of Ion Implantation Parameters

[0065] This embodiment improves the formation efficiency and optical properties of color centers by optimizing ion implantation parameters. Based on Embodiment 1 or Embodiment 2, the ion implantation energy and dose are adjusted, for example, at 10 keV and 1*10 12 / cm 2 Ion implantation was performed at a dose of [specific value].

[0066] Example 5: Pattern Design of Nanopore Arrays

[0067] This embodiment explores the influence of different nanopore array patterns on the performance of color center arrays. Based on Embodiment 1 or Embodiment 2, it mainly designs and fabricates nanopore arrays of different shapes and arrangements based on laser annealing micro-nano positioning and region shape customization by optical field shaping or action space control, in order to meet the different spacing and size requirements of color center arrays for specific applications.

Claims

1. A method for preparing a diamond color center array based on a polymer phase-separated nanomask, characterized in that, Two options are included: Option 1 involves obtaining a nanopore array pattern through polymer phase separation and assembly, transferring the nanopore array pattern to a hard mask layer on a diamond surface, and then using the nanopore array hard mask to prepare a color center array via ion implantation. The specific steps are as follows: Step S1: Pre-treat the diamond surface to remove organic and inorganic impurities, providing a clean surface for subsequent processes, and obtain the pre-treated diamond surface. Step S2: Prepare a hard mask layer on the pretreated diamond surface. The hard mask layer is made of silicon thin film, or oxide thin film or metal thin film; the film thickness is less than 200 nm. Step S3: Apply an adhesive layer onto the hard mask layer to enhance the adhesion between the polymer material and the hard mask; Step S4: Coat the adhesive layer with a phase-separable patterned polymer material to form nanoscale patterns using its self-assembly properties; Step S5: Anneal the selected areas of the thin film formed in step S4 to induce and regulate the phase separation structure of the polymer material, form a uniform nanomask, and enhance the pattern clarity; Step S6: Etch the sample after annealing phase separation and assembly, transfer the obtained pattern to the substrate, etch the hard mask layer, and obtain the nanomask layer of the nanopore array; Step S7: Under the protection of a nanomask, nitrogen ions are injected into diamond to form a regular array of NV color centers; Step S8: Use wet acid washing or dry reactive ion etching to remove the hard mask and expose the diamond surface implantation area; Step S9: Perform nitrogen ion implantation and high-temperature annealing in a vacuum environment to activate the color center and improve its optical properties; Step S10: Post-process the diamond NV color center array to obtain a diamond NV color center array with a clear and stable pattern; Option 2, the specific steps are as follows: Step S1: Pre-treat the diamond surface to remove organic and inorganic impurities, and obtain the pre-treated diamond surface. Step S2: Directly coat the pretreated diamond surface with a high-χ value block copolymer polymer film with high Flory-Huggins interaction parameter value, or amyloid protein and DNA self-assembling biomacromolecules to form nanoscale patterns. The film thickness is greater than 200 nm, which is called a thick film compared to the film with a thickness of less than 200 nm in Scheme 1. Step S3: Perform laser or solvent annealing on the block copolymer polymer film to improve the phase separation structure of the block copolymer polymer material; annealing is not required for the biomacromolecule film; Step S4: Etch the assembled sample to obtain a nanomask layer with a nanopore array; Step S5: Directly use the polymer thick film after phase separation, assembly, and selective etching as a mask to perform nitrogen ion implantation to form color centers; Step S6: After nitrogen ion implantation, the polymer layer is removed by acid washing; Step S7: Perform high-temperature annealing in a vacuum environment to activate the color centers; Step S8: Acid-wash the diamond NV color center array to improve the quality of the color centers.

2. The preparation method according to claim 1, characterized in that, In Option 1: In step S2, in the hard mask layer, the silicon thin film is prepared by spin coating and has a thickness of 50-100 nm; the oxide thin film or metal thin film is prepared by thermal evaporation, ALD, CVD or magnetron sputtering processes and has a thickness of 10-50 nm. The oxide thin film material is silicon dioxide or titanium dioxide, and the metal thin film material is aluminum. In step S3, the adhesive layer material, for the block copolymer of the polymer material used, is selected as a molecular brush layer composed of two segments or a non-block homopolymer molecular felt layer, with a thickness of 10-20 nm. In step S4, the phase-separable patterned polymer material is a diblock copolymer PS-b-PMMA; In step S5, the annealing is performed by laser annealing, overall thermal annealing, or solvent-induced phase separation annealing. In step S7, the nitrogen ion implantation energy is 10-200 keV, and the implantation dose is 1×10⁻⁶. 12 -1×10 14 / cm 2 ; In step S8, the acid is selected from nitric acid, sulfuric acid, and perchloric acid; In step S9, the high-temperature annealing temperature is 800-1100℃, and the time is 1-2 hours.

3. The preparation method according to claim 1, characterized in that, The size and spacing of the color center array can be controlled by controlling the polymer phase separation and ion implantation conditions; The size range of the color center distribution points is 10nm-100nm; the distance between the color centers ranges from 10nm to 100nm.

4. The preparation method according to claim 1, characterized in that, In Option 2: In step S2, the high χ-value block copolymer polymer material is PS-b-P2VP or PS-b-PDMS, with a χ-value greater than 0.07 and less than 0.1 at 150°C.

5. The preparation method according to claim 4, characterized in that, The size and spacing of the color center array can be controlled by controlling the polymer phase separation and ion implantation conditions; The size range of the color center distribution points is 10nm-100nm; the distance between the color centers ranges from 10nm to 100nm.

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