Stepped double-mesa NV color center diamond scanning probe and its preparation method

Abstract

This application proposes a stepped double-mesa NV center diamond scanning probe, comprising a waveguide structure containing NV centers, a first mesa, and two mesa arranged in a stepped manner from top to bottom; wherein the height of the waveguide structure is h1, the height of the first mesa is h2, the step length of the first mesa is l2, the height of the second mesa is h3, and the step length of the second mesa is l3. This application also proposes a method for fabricating the aforementioned NV center diamond scanning probe.

Description

Technical Field

[0001] This application relates to the field of diamond AFM scanning sensing probe technology, specifically to a stepped double-mesa NV color center diamond scanning probe and its preparation method. Background Technology

[0002] Nitrogen-vacancy (NV) centers, as typical spin defects in diamond, possess advantages such as stable operation at room temperature, convenient optical readout, and long spin coherence time, enabling high-precision sensing of physical quantities such as electromagnetic fields and temperature. Combining diamond's excellent wear resistance and chemical inertness with atomic force scanning systems has become an important technological direction in the fields of nanoscale scanning imaging and micro / nano sensing.

[0003] In related technologies, various diamond scanning probe schemes based on NV centers have been developed. Examples include diamond nanopillar waveguide array sensors containing NV centers, and NV center diamond AFM probes with cantilever beam structures. In addition, there are also researches using laser cutting and focused ion beam milling techniques to fabricate diamond NV probes. However, existing schemes still have significant shortcomings in terms of structural design and fabrication processes.

[0004] In terms of structural design, traditional single-stage probes have inherent conflicts: while larger stages facilitate bonding and assembly with AFM systems, slight tilting during leveling and scanning can prevent NV color centers from contacting the sample; smaller stages or cantilever beam structures can improve tilt adaptation, but the small size of the stage makes assembly time-consuming and cumbersome, reducing assembly efficiency and easily introducing assembly errors. Regarding fabrication processes, the method of using focused ion beams to process scanning probes on diamond stages has low processing efficiency, and the ion beam can easily damage the properties of color centers, affecting sensing performance. The fabrication process of traditional cantilever beam probes is also complex, with a lack of hierarchical consideration in stage size and layout design, further increasing assembly difficulty and usage risks.

[0005] Therefore, optimizing the structural design of diamond scanning probes to balance ease of assembly and scanning angle tolerance, while simplifying the manufacturing process and reducing damage to color centers, is a technical problem that urgently needs to be solved in this field. Summary of the Invention

[0006] In view of this, in order to solve at least one technical problem in related technologies and other aspects, this application proposes a stepped double-mesa NV center diamond scanning probe, including a waveguide structure containing NV centers, a first mesa and a second mesa arranged in a stepped manner from top to bottom;

[0007] The waveguide structure has a height of h1, a first platform height of h2, a step length of l2, a second platform height of h3, and a step length of l3.

[0008] .

[0009] According to embodiments of this application, the NV color center is located 2-50 nm below the surface of the waveguide structure; the waveguide structure containing the NV color center is cylindrical, parabolic, or frustum-shaped; 100 nm ≤ h1 ≤ 2 μm.

[0010] According to an embodiment of this application, the shapes of the first tabletop and the second tabletop are each independently selected from any one of a square, a rectangle, or a circle; the side length or diameter of the first tabletop is a1, 1≤a1≤100μm, and the side length or diameter of the second tabletop is a2, 50≤a2≤600μm, a1<a2.

[0011] According to embodiments of this application, the scanning angle tolerance of the NV color center diamond scanning probe during operation is no greater than 10°.

[0012] According to an embodiment of this application, the first platform is adapted to accommodate the tilt angle of the sample during scanning, and the second platform is adapted for assembly and fixation.

[0013] In another aspect of this application, a method for preparing an NV color center diamond scanning probe as described above is also proposed, comprising:

[0014] Provide diamond substrate;

[0015] A waveguide structure including at least one NV color center is formed in a first region of a diamond substrate;

[0016] A first patterning process is performed on the surface of a diamond substrate with a waveguide structure to form a first mask layer, which covers a predetermined area of ​​the waveguide structure and the first mesa.

[0017] Using the first mask layer as a cover, the diamond substrate is etched for the first time to form the first mesa;

[0018] Fix the first mesa of the diamond substrate to the temporary support substrate;

[0019] A second patterning process is performed on the surface of the diamond substrate facing away from the first mesa to form a second mask layer, which corresponds to a predetermined second mesa region.

[0020] Using the second mask layer as a cover, the diamond substrate is etched a second time to form the second mesa;

[0021] The remaining mask layer was removed, and the first mesa was peeled off from the temporary support substrate to obtain the NV color center diamond scanning probe with a stepped double mesa.

[0022] According to an embodiment of this application, in the step of forming a waveguide structure including at least one NV color center in a first region of a diamond substrate, an NV color center precursor is formed by nitrogen ion implantation, and then the NV color center precursor is annealed to obtain the NV color center; wherein, the implantation dose in the nitrogen ion implantation process is 1×10⁻⁶. 10 ~1×10 14 ions / cm 2 The injection energy is 1~40keV, and the NV color center precursor is located 2~50nm below the surface of the diamond substrate.

[0023] In the annealing process, the annealing temperature is 800~1200℃, the annealing time is 2~6h, and the annealing atmosphere is vacuum or inert atmosphere.

[0024] Under annealing atmosphere of vacuum, the vacuum level shall not be less than 1×10⁻⁶. -5 Pa;

[0025] Under inert annealing conditions, the purity of the inert gas shall not be less than 99%.

[0026] According to an embodiment of this application, the aforementioned preparation method further includes: after forming a waveguide structure including at least one NV color center in a first region of a diamond substrate, forming overlay marks for photolithography alignment on the diamond substrate.

[0027] According to an embodiment of this application, the first patterning process includes: spin-coating photoresist onto the surface of a diamond substrate on which a waveguide structure is formed to cover the waveguide structure; determining the area of ​​the first mesa by overlay marking and performing a first exposure process; depositing metal material in the area of ​​the first mesa after the first exposure process; removing the photoresist and the metal material deposited on the photoresist; and forming a first mask layer with the metal deposited in the remaining area of ​​the first mesa.

[0028] The second patterning process includes: spin-coating photoresist on the surface of a diamond substrate facing away from the first mesa, determining the area of ​​the second mesa by overlay marking and performing a second exposure process, depositing metal material in the area of ​​the second mesa after the second exposure process, removing the photoresist and the metal material deposited on the photoresist, and the metal deposited in the remaining area of ​​the second mesa forms a second mask layer.

[0029] According to embodiments of this application, the aforementioned preparation method further includes:

[0030] After the first mesa was peeled off from the temporary support substrate, the NV color center diamond scanning probe was acid-washed using a combination of perchloric acid, nitric acid, and sulfuric acid.

[0031] According to embodiments of this application, functional zoning is first achieved by setting a waveguide structure with increasing dimensions from top to bottom, a first mesa, and a second mesa. The larger second mesa provides ample operating space for the bonding and assembly of the probe and the AFM system, reducing assembly difficulty and errors; the smaller first mesa serves as an adaptation unit for the scanning process, reducing the volume of the probe tip and thus improving the tolerance for tilt angles during scanning, solving the problem that a large mesa is prone to failure to contact the sample due to tilt. Secondly, by limiting the dimensional proportions of each component, this application ensures that the waveguide structure can still stably contact the sample surface when the probe has a certain tilt angle, avoiding scanning failures caused by mismatched design parameters, thus ensuring both assembly stability and reliability in scanning use. Attached Figure Description

[0032] Figure 1 This is a schematic diagram of the structure of the NV color center diamond scanning probe in an embodiment of this application;

[0033] Figure 2 This is a comparison diagram of the working status of the NV color center diamond scanning probe and the conventional probe in the embodiments of this application, wherein a is the NV color center diamond scanning probe in the embodiments of this application and b is the NV color center diamond scanning probe of the conventional probe.

[0034] Figure 3 This is a schematic diagram showing the dimensional relationship of the stepped double-mesa NV color center diamond scanning probe in an embodiment of this application;

[0035] Figure 4 Flowchart of the method for preparing NV color center diamond scanning probe in this application embodiment;

[0036] Figure 5 This is a schematic diagram of the diamond substrate structure in Embodiment 1 of this application;

[0037] Figure 6 This is a schematic diagram of the waveguide structure and overlay markings in Embodiment 1 of this application;

[0038] Figure 7 This is a schematic diagram of the structure of the first tabletop in Embodiment 1 of this application;

[0039] Figure 8 This is a schematic diagram of the structure of the temporary support substrate in Embodiment 1 of this application;

[0040] Figure 9 This is a schematic diagram of the structure of the second mesa etched in Embodiment 1 of this application;

[0041] Figure 10 This is a schematic diagram of the structure of the stepped double-mesa NV color center diamond scanning probe array prepared in Example 1 of this application.

[0042] [Attached image labels]

[0043] In this application, the reference numerals used in the drawings have the following meanings:

[0044] 1- Waveguide structure;

[0045] 2-First countertop;

[0046] 3-Second countertop;

[0047] 4-Diamond substrate;

[0048] 5-overlay markings;

[0049] 6-UV curing adhesive;

[0050] 7- Temporary support substrate. Detailed Implementation

[0051] To make the objectives, technical solutions, and advantages of this application clearer, the following detailed description is provided in conjunction with specific embodiments and the accompanying drawings.

[0052] The endpoints and any values ​​of the ranges disclosed in this application are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of the various ranges, the endpoint values ​​of the various ranges and individual point values, and individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed in this application.

[0053] The terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the scope of this application. The terms “comprising,” “including,” etc., as used herein indicate the presence of the stated features, steps, operations, and / or components, but do not exclude the presence or addition of one or more other features, steps, operations, or components.

[0054] All terms used herein (including technical and scientific terms) have the meanings commonly understood by those skilled in the art, unless otherwise defined. It should be noted that the terms used herein are to be interpreted in a manner consistent with the context of this specification, and not in an idealized or overly rigid way.

[0055] It should be noted that, unless otherwise defined, the technical or scientific terms used in this application should have the ordinary meaning understood by a person with ordinary skill in the art to which this application pertains. Where the terms "first," "second," etc., are used throughout, they are used only to distinguish similar objects and should not be construed as indicating or implying their relative importance, order of precedence, or implicitly specifying the number of technical features indicated. It should be understood that the data in the descriptions of "first," "second," etc., can be interchanged where appropriate.

[0056] In this application, unless otherwise expressly specified and limited, the terms "installation," "connection," "linking," and "fixing," etc., should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral part; they can refer to a mechanical connection, an electrical connection, or a connection that allows communication between them; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal communication between two components or the interaction between two components. Those skilled in the art can understand the specific meaning of the above terms in this application according to the specific circumstances.

[0057] In the description of this application, it should be understood that the terms "longitudinal", "length", "circumferential", "front", "rear", "left", "right", "top", "bottom", "inner", "outer", etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this application and simplifying the description, and do not indicate or imply that the subsystem or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this application.

[0058] Throughout the accompanying drawings, identical elements are represented by the same or similar reference numerals. Conventional structures or configurations will be omitted where they may cause confusion in understanding this application. Furthermore, the shapes, dimensions, and positional relationships of the components in the drawings do not reflect their actual size, scale, or actual positional relationships. Additionally, any reference symbols placed within parentheses in this application should not be construed as limiting the scope of this application.

[0059] Similarly, to simplify this application and aid in understanding one or more of the various disclosed aspects, in the above description of exemplary embodiments of this application, various features of this application are sometimes grouped together into a single embodiment, figure, or description thereof. The use of terms such as "one embodiment," "some embodiments," "example," "specific example," or "some examples," etc., indicates that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of this application. In this specification, illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples.

[0060] Furthermore, the technical solutions of the various embodiments can be combined with each other, but only if they are based on the ability of those skilled in the art to implement them. When the combination of technical solutions is contradictory or cannot be implemented, it should be considered that such combination of technical solutions does not exist and is not within the scope of protection claimed in this application.

[0061] Figure 2 This is a comparison diagram of the working status of the NV color center diamond scanning probe and the conventional probe in the embodiments of this application, wherein a is the NV color center diamond scanning probe in the embodiments of this application and b is the NV color center diamond scanning probe of the conventional probe.

[0062] In the process of implementing this application, it was discovered that, Figure 2 As shown in b, the reason why existing diamond scanning probes struggle to balance ease of assembly and scanning angle tolerance lies in bundling the two functions of assembly support and scanning adaptation onto the same platform structure. Assembly requires a large operating surface, while scanning requires a compact tip to avoid tilt interference. These two requirements inherently conflict in terms of spatial dimensions, which a single platform cannot simultaneously satisfy. Therefore, as... Figure 2 As shown in section a, this application attempts to decouple the two functions, conceiving a stepped dual-mesa structure: a large second mesa ensures assembly operations, while a small first mesa enhances scanning adaptability. Further analysis revealed that simply having two mesas is insufficient to guarantee scanning reliability; quantitative constraints must also be placed on the geometric ratio of the height of the two mesas to the step length to ensure that the waveguide structure always preferentially contacts the sample within the allowable tilt range, thus forming a complete stepped dual-mesa probe scheme.

[0063] Figure 1 This is a schematic diagram of the structure of the NV color center diamond scanning probe in the embodiments of this application. Figure 3 This is a schematic diagram showing the dimensional relationship of the NV color center diamond scanning probe in an embodiment of this application.

[0064] This application proposes a stepped, dual-mesa NV color center diamond scanning probe, such as... Figure 1 As shown, it includes a waveguide structure 1 containing NV color centers, a first mesa 2, and a second mesa 3 arranged in a stepped manner from top to bottom;

[0065] Among them, such as Figure 3 As shown, the height of waveguide structure 1 is h1, the height of the first platform 2 is h2, the step length of the first platform 2 is l2, the height of the second platform 3 is h3, and the step length of the second platform 3 is l3. .

[0066] According to embodiments of this application, functional partitioning is achieved by setting waveguide structure 1, first mesa 2, and second mesa 3 with increasing dimensions from top to bottom. The larger second mesa 3 provides ample operating space for the adhesion and assembly of the probe and the AFM system, reducing assembly difficulty and errors; the smaller first mesa 2 serves as an adaptation unit for the scanning process, reducing the volume of the probe tip and thus improving the tolerance for tilt angles during scanning, solving the problem that large mesa surfaces are prone to failure to contact the sample due to tilt. Secondly, by limiting the dimensional ratio of each component, this application ensures that waveguide structure 1 can still stably contact the sample surface when the probe has a certain tilt angle, avoiding scanning failures caused by mismatched design parameters, ensuring assembly stability while also considering the reliability of scanning use.

[0067] According to an embodiment of this application, the NV color center is located 2-50 nm below the surface of the waveguide structure 1; the waveguide structure 1 containing the NV color center is cylindrical, parabolic, or frustum-shaped; 100 nm ≤ h1 ≤ 2 μm.

[0068] In the embodiments of this application, the NV color center is positioned 2-50 nm below the surface of waveguide structure 1. This avoids interference from spin noise caused by surface dangling bonds or contaminants due to the color center being too close to the surface, ensuring coherence time, and also ensures a sufficiently close distance between the color center and the sample to maintain high spatial resolution and sensing sensitivity. The height h1 of waveguide structure 1 is controlled between 100 nm and 2 μm, ensuring that waveguide structure 1 has sufficient mechanical strength to withstand scanning contact, while also preventing it from increasing the risk of breakage due to excessive length when the probe is tilted. This ensures structural stability while achieving reliable sample contact in conjunction with the first mesa 2 and the second mesa 3.

[0069] In some specific embodiments, the waveguide structure 1 containing NV color centers serves as the core sensing unit, and is vertically disposed in the area above the first platform 2 (the center position does not need to be limited, and the layout can be flexibly arranged according to scanning requirements), containing at least one NV color center.

[0070] According to the embodiments of this application, the shapes of the first platform 2 and the second platform 3 are each independently selected from any one of square, rectangle or circle; the side length or diameter of the first platform 2 is a1, 1≤a1≤100μm, and the side length or diameter of the second platform 3 is a2, 50≤a2≤600μm, a1<a2.

[0071] According to the embodiments of this application, when the probe is tilted, the smaller size of the first stage 2 effectively prevents the stage sidewall from contacting the sample before the waveguide structure 1, thereby improving the scanning angle tolerance. The second stage 3 is significantly larger than the first stage 2, providing ample space and bonding area for adhesion operations during use, reducing assembly difficulty and alignment errors. Through the dimensional gradient design of a1 and a2, the probe simultaneously possesses convenient and stable assembly characteristics and high-tolerance scanning adaptability, solving the inherent problem that a single stage cannot adequately handle both assembly and scanning.

[0072] According to embodiments of this application, the scanning angle tolerance of the NV color center diamond scanning probe during operation is no greater than 10°.

[0073] According to embodiments of this application, "scanning angle tolerance of no more than 10°" means that when there is an inclination of no more than 10° between the probe and the sample surface, the waveguide structure 1 containing the NV color center can still stably contact the sample under test. This is related to the size gradient design of the dual-stage platform and the key proportional constraint relationship. The smaller first stage 2 will not touch the sample before the waveguide structure 1 when tilted, thus ensuring that the sensing unit is always at the forefront of the scan. The achievement of this angle tolerance significantly reduces the requirements for probe assembly accuracy and system leveling, allowing the installation process to be completed without cumbersome calibration. At the same time, in actual scanning, even if there are slight undulations on the sample surface or installation deviations, the probe can still work reliably, improving the ease of use of the equipment and the scanning success rate.

[0074] According to an embodiment of this application, the first platform 2 is adapted to accommodate the tilt angle of the sample during scanning, and the second platform 3 is adapted for assembly and fixation.

[0075] According to an embodiment of this application, the first stage 2 is smaller in size, suitable for adapting to the tilt angle of the sample during scanning: when there is a certain angle between the probe and the sample surface, the first stage 2 will not contact the sample before the waveguide structure 1 due to its excessive size, thereby ensuring that the waveguide structure 1, including the NV color center, can stably approach the area to be measured, improving scanning reliability and signal acquisition quality. The second stage 3 is larger in size, suitable for assembly and fixation: its ample surface area facilitates the bonding operation with the AFM system base or tuning fork, reducing assembly difficulty and alignment errors, and enhancing the stability of the probe after installation. Through the division of labor and cooperation between the first stage 2 and the second stage 3, the probe achieves both scanning adaptability and assembly convenience within the same structure.

[0076] Figure 4 This application provides a flowchart of the method for preparing NV color center diamond scanning probes.

[0077] In another aspect of this application, a method for preparing an NV color center diamond scanning probe as described above is also proposed, comprising the following steps S1 to S8:

[0078] Step S1: Provide a diamond substrate 4;

[0079] Step S2: Form a waveguide structure 1 including at least one NV color center in the first region of the diamond substrate 4;

[0080] Step S3: Perform a first patterning process on the surface of the diamond substrate 4 on which the waveguide structure 1 is formed to form a first mask layer, the first mask layer covering a predetermined area of ​​the waveguide structure 1 and the first mesa 2.

[0081] Step S4: Using the first mask layer as a cover, the diamond substrate 4 is etched for the first time to form the first mesa 2;

[0082] Step S5: Fix the first mesa 2 of the diamond substrate 4 to the temporary support substrate 7;

[0083] Step S6: Perform a second patterning process on the surface of the diamond substrate 4 facing away from the first mesa 2 to form a second mask layer, which corresponds to the preset second mesa 3 region;

[0084] Step S7: Using the second mask layer as a cover, the diamond substrate 4 is etched a second time to form the second mesa 3;

[0085] Step S8: Remove the remaining mask layer and peel the first mesa 2 off the temporary support substrate 7 to obtain the stepped double mesa NV color center diamond scanning probe.

[0086] According to embodiments of this application, a step-by-step processing method involving two patterning and etching steps is employed: firstly, a waveguide structure 1 is formed in a first region of a diamond substrate 4; then, a first mesa 2 is formed through a first patterning and etching process; finally, after fixing the first mesa 2 to a temporary support substrate 7, a second patterning and etching process is performed from the back of the diamond substrate 4 to form a second mesa 3. This process ensures that the formation of the two mesas is independent and sequentially controllable, avoiding the complexity and alignment difficulties associated with processing two mesas simultaneously in a single etching operation. Furthermore, the entire fabrication process is based on mature technologies such as photolithography and etching, eliminating the need for point-by-point milling using focused ion beams, thus improving processing efficiency and avoiding potential damage to the diamond lattice and NV color center properties from high-energy ion beams. The introduction of the temporary support substrate 7 effectively protects the fabricated waveguide structure 1 and the first mesa 2 from damage during subsequent etching, ensuring the integrity and yield of the final probe structure.

[0087] According to an embodiment of this application, in the process of forming a waveguide structure 1 including at least one NV color center in the first region of the diamond substrate 4 in step S2, an NV color center precursor is formed by nitrogen ion implantation, and then the NV color center precursor is annealed to obtain the NV color center; wherein, the implantation dose of the nitrogen ion implantation process is 1×10⁻⁶. 10 ~1×10 14 ions / cm 2 The injection energy is 1~40keV, and the NV color center precursor is located 2~50nm below the surface of the diamond substrate 4.

[0088] In the annealing process, the annealing temperature is 800~1200℃, for example, it can be 800℃, 900℃, 1000℃, 1100℃, 1200℃ or any two of these, and the annealing time is 2~6h, for example, it can be 2h, 3h, 4h, 5h, 6h or any two of these, and the annealing atmosphere is a vacuum or an inert atmosphere.

[0089] Under annealing atmosphere of vacuum, the vacuum level shall not be less than 1×10⁻⁶. -5 Pa;

[0090] Under inert annealing conditions, the purity of the inert gas shall not be less than 99%.

[0091] According to embodiments of this application, by controlling the process conditions of nitrogen ion implantation and annealing, the controllable formation and performance optimization of NV centers within waveguide structure 1 are achieved. Controlling the implantation dose ensures a sufficient number of vacancies are formed in the diamond lattice to combine with nitrogen and generate NV centers, while avoiding excessive lattice damage due to excessive dose, which would affect the coherence time of the centers. Controlling the implantation energy facilitates controlling the implantation depth to 2-50 nm below the surface. This depth ensures the near-field interaction strength between the NV centers and the sample under test, meeting the requirements of high-sensitivity sensing, while preventing the centers from being too close to the surface and subject to surface noise interference. Controlling the annealing temperature and annealing atmosphere effectively repairs lattice damage generated during implantation, promotes vacancy migration and combination with nitrogen to form stable NV centers, and prevents graphitization or oxidation of the diamond surface at high temperatures, thereby ensuring the optical quality and spin characteristics of the centers.

[0092] According to an embodiment of this application, step S2 of the aforementioned preparation method further includes: after forming a waveguide structure 1 including at least one NV color center in a first region of the diamond substrate 4, forming an overlay mark 5 for photolithography alignment on the diamond substrate 4.

[0093] According to an embodiment of this application, an overlay mark 5 is prepared on a diamond substrate 4 while the waveguide structure 1 is being formed, providing a reliable alignment reference for subsequent photolithography processes.

[0094] In some specific embodiments, the waveguide structure 1 and the overlay mark 5 are fabricated simultaneously using an ICP-RIE etching process. The etching gas is selected from O2 or a mixture of O2 and CF3 or a mixture of O2 and SF6 (the etching gas is selected according to the shape of the waveguide structure 1).

[0095] In some specific embodiments, the overlay mark 5 is cross-shaped or square, with a line width of not less than 10 μm, and is formed using the same etching process as the waveguide structure 1 to ensure overlay accuracy.

[0096] According to an embodiment of this application, in step S3, the first patterning process includes: spin-coating photoresist onto the surface of a diamond substrate on which the waveguide structure is formed to cover the waveguide structure; determining the area of ​​the first mesa by overlay marking and performing a first exposure process; depositing metal material in the area of ​​the first mesa after the first exposure process; removing the photoresist and the metal material deposited on the photoresist; and forming a first mask layer with the metal deposited in the remaining area of ​​the first mesa.

[0097] In step S6, the second patterning process includes: spin-coating photoresist on the surface of a diamond substrate facing away from the first mesa, determining the area of ​​the second mesa by overlay marking and performing a second exposure process, depositing metal material in the area of ​​the second mesa after the second exposure process, removing the photoresist and the metal material deposited on the photoresist, and then forming a second mask layer with the metal deposited in the remaining area of ​​the second mesa.

[0098] According to embodiments of this application, a first mask layer and a second mask layer are formed through two patterning processes, laying the foundation for the precise forming of a stepped double mesa. Each patterning process employs a process of photoresist spin coating, alignment with overlay marks 5, exposure and development, and metal deposition, followed by dissolution and stripping, ensuring precise correspondence between the mask pattern and the preset area. The use of overlay marks 5 allows for alignment of the two patterning processes based on the same reference, avoiding accumulated errors. The selection of a metal material as the mask layer, with its thickness and etching resistance, effectively protects the underlying waveguide structure 1 and the mesa area from damage during subsequent dry etching. Simultaneously, the dissolution and stripping process enables clean transfer of the photoresist pattern to the metal mask, reducing the impact of residues on subsequent processes.

[0099] In some specific embodiments, since the first mask layer also serves to protect the waveguide during the entire first etching process, the first mask layer still needs to be strictly higher than the waveguide structure 1 after the first etching in step S4. In some specific embodiments, this application avoids relying on complex and inefficient focused ion beam fine processing, and adopts mature photolithography and etching processes to reduce the risk of color center damage and improve fabrication efficiency.

[0100] In some specific embodiments, the first patterning process includes:

[0101] Photoresist is spin-coated onto the surface of the diamond substrate 4. The thickness of the photoresist is higher than the height of the probe structure of the waveguide structure 1 to ensure that the waveguide structure 1 is completely covered. According to the preset positional relationship between the waveguide structure 1 and the first mesa 2, the pattern of the first mesa 2 is photolithographically etched onto the photoresist layer using the overlay mark 5 in step S1. The overlay error of the overlay process is better than 5μm to improve the alignment accuracy of the structure. Electron beam photoresist or ultraviolet photoresist is selected as the photoresist, with ultraviolet photoresist preferred, which facilitates pattern observation and accuracy control during the overlay process.

[0102] The mask material is deposited by sputtering, evaporation or vapor deposition. The mask material includes metals and their metal oxides, non-metals and their oxides, preferably titanium or chromium. The deposition thickness is higher than that of waveguide structure 1 to ensure that waveguide structure 1 is protected from damage during the etching process. The photoresist layer is removed by a lift-off process to transfer the pattern of the first mesa 2 into the etching protection mask pattern. The reagent used for the lift-off process is determined by the photoresist.

[0103] Dry etching processes, including but not limited to reactive ion etching, plasma etching, and inductively coupled plasma etching, are used to etch the diamond substrate 4. The waveguide structure 1 containing the NV color center and the first mesa 2 are protected by a mask material, while the remaining areas are etched to form the first mesa 2. The etching depth can be flexibly adjusted according to design requirements. After etching, the surface mask material is removed by wet etching to avoid residual impurities affecting subsequent processes.

[0104] In some specific embodiments, the second patterning process includes:

[0105] The diamond substrate 4 containing the waveguide structure 1 and the first mesa 2 is inverted and bonded to the temporary support substrate 7 (including but not limited to quartz sheets and silicon wafers with a thickness of 0.3-1mm). The bonding method includes but is not limited to UV-curable adhesive, AB adhesive, thermosetting adhesive, etc., to ensure that the waveguide structure 1 and the first mesa 2 are completely attached to the support substrate and to avoid damage during the etching of the second mesa 3.

[0106] Using the overlay mark 5 in step S2, a photolithography, mask deposition, dissolution and stripping, and dry etching process similar to the first patterning process is adopted. At this time, the mask thickness is adjusted according to the etching requirements, and finally the remaining thickness of the diamond is etched through to form a second mesa 3 that is distinct from the first mesa 2. After the etching is completed, the surface mask material is removed.

[0107] According to embodiments of this application, the aforementioned preparation method further includes:

[0108] Step S9: After the first mesa 2 is peeled off from the temporary support substrate 7, the NV color center diamond scanning probe is acid-washed. The acid-washing solution is a combination acid solution including perchloric acid, nitric acid and sulfuric acid.

[0109] According to embodiments of this application, acid washing of the stripped probe with a combined acid solution is beneficial for removing various contaminants remaining on the probe surface during the fabrication process, including organic residues from photoresist, mask material debris, and adhesive used for temporary fixation. After washing, the probe is rinsed with deionized water until neutral to avoid the influence of residual acid on subsequent use. This acid washing step ensures that the final probe surface is clean and free of impurities, which helps maintain the optical performance and sensing stability of the NV color center.

[0110] In some specific embodiments, the prepared probe is peeled off from the temporary support substrate 7 and cleaned with a tri-acid solution (perchloric acid: nitric acid: sulfuric acid = 1:1:1) at 200-300°C for 3-6 hours to remove photoresist residue, mask debris and adhesive. Then it is rinsed with deionized water until neutral and dried to obtain the finished probe.

[0111] In some specific embodiments, the sum of the heights of the waveguide height h1 including the NV color center, the height h2 of the first mesa 2, and the height h3 of the second mesa 3 is equal to the thickness H of the initial diamond substrate 4.

[0112] It should be noted that the described embodiments are merely some, not all, of the embodiments described in this application. Other embodiments obtained by those skilled in the art based on the embodiments described in this application without inventive effort are all within the scope of protection of this application.

[0113] Example 1

[0114] In this embodiment, a stepped double-mesa NV center diamond scanning probe array was fabricated, comprising a nanopillar waveguide structure 1 containing NV centers, a first mesa 2, and a second mesa 3. The three are arranged in a stepped hierarchical structure, with the waveguide structure 1 containing NV centers located above the first mesa 2, and the first mesa 2 located above the second mesa 3. The waveguide structure 1 is in the form of a nanopillar.

[0115] Specifically, the NV color center sensing unit in the nanopillar waveguide structure 1 containing NV color centers is formed through nitrogen ion implantation and annealing. The implantation dose is 6 × 10⁻⁶. 10 ions / cm 2The annealing temperature is 1000℃, and the NV color center is located 10nm below the surface of waveguide structure 1. The waveguide structure 1 of the nanopillar is frustum-shaped with a height of 440nm and a diameter of 380nm. The first mesa 2 is square with a side length of 10μm and a height of 30μm. The second mesa 3 is square with a side length of 380μm and a height of 20μm.

[0116] The specific steps are as follows:

[0117] Figure 5 This is a schematic diagram of the diamond substrate structure in Embodiment 1 of this application.

[0118] Step S101: As Figure 5 As shown, a type IIa chemical vapor deposition (CVD) diamond substrate 4 with a (100) crystal orientation and a thickness H of 50 μm was selected. The diamond substrate 4 was subjected to N24 ... 14 Ion implantation, with an implantation dose of 6 × 10⁻⁶ 10 ions / cm 2 The energy injected was 7keV, and then annealed in an ultra-high vacuum environment at 1000℃ for 2 hours to form NV color centers.

[0119] Subsequently, the surface was cleaned in a tri-acid solution (perchloric acid: nitric acid: sulfuric acid = 1:1:1) at 300°C for 4 hours to remove surface carbonization and contaminants; electron beam photoresist FOX-15 was spin-coated onto the diamond substrate 4 (with a spin coating rate of 6000 rpm and a baking temperature of 180°C for 7 min) to a thickness of approximately 380 nm.

[0120] Figure 6 This is a schematic diagram of the waveguide structure and overprinted markings in Embodiment 1 of this application.

[0121] Step S102: As Figure 6 As shown, the pattern of the designed cross-shaped overlay mark 5 along with the waveguide structure 1 is transferred onto the photoresist by electron beam lithography exposure and subsequent development (development with 25% TMAH developer for 5 min; fixing with deionized water for 2 min, followed by drying with nitrogen).

[0122] The diamond substrate 4 was etched using oxygen (gas flow rate of 30 sccm; etching power RF 100W, ICP 3000W; etching pressure 10 mTorr) to form a cross-shaped overlay mark 5 and a waveguide structure 1. Subsequently, the HSQ mask on the diamond surface was cleaned using a buffered oxide etchant (BOE) solution. At this time, the waveguide structure 1 contained NV color centers. The nanopillar waveguide structure 1 is frustum-shaped with a height of 440 nm and a diameter of 380 nm. The linewidth of the overlay mark 5 is 10 μm and the height is 440 nm.

[0123] Figure 7This is a schematic diagram of the structure of the first tabletop in Embodiment 1 of this application.

[0124] Step S103: Spin-coat the diamond substrate 4 with UV photoresist AZ6112 (coating speed 4000 rpm; time 30 s), the photoresist thickness is about 1.2 μm, which is higher than the height of the nanopillar waveguide structure 1 containing the color center; using the overlay mark 5, the pattern of the first mesa 2 with a side length of 10 μm square is photolithographically etched onto the photoresist layer using the overlay process. The waveguide structure 1 containing the NV color center is located square, that is, at the center of the pattern of the first mesa 2. The overlay error is controlled within 3 μm; after the overlay is completed, develop with developer AZ300MIF for 60 s; fix with deionized water for 30 s, and then dry with nitrogen.

[0125] A titanium mask with a thickness of 800 nm was deposited by electron beam evaporation. The ultraviolet photoresist AZ6112 was stripped using patterned N-methylpyrrolidone (NMP) to transfer the square pattern of the first mesa 2 onto the titanium mask.

[0126] The diamond substrate 4 was etched using inductively coupled plasma etching (ICP) with oxygen (gas flow rate 30 sccm; etching power RF 100W, ICP 3000W; etching pressure 5 mTorr) to a depth of 30 μm. Figure 7 As shown, the first mesa 2 is formed; after etching, the titanium mask material is removed by titanium etching solution treatment.

[0127] Figure 8 This is a schematic diagram of the structure of the temporary support substrate in Embodiment 1 of this application.

[0128] Step S104: As Figure 8 As shown, the waveguide structure 1 containing the color center, the first mesa 2, and the remaining diamond substrate 4 are inverted and bonded to a square temporary support substrate 7 (made of quartz, with a thickness of 500 nm and a side length of 15 mm) using UV-curable adhesive 6. This ensures that the waveguide structure 1 containing the color center and the first mesa 2 are completely attached to the temporary support substrate 7, thus avoiding damage to the waveguide structure 1 containing the color center and the first mesa 2 during the etching process of the second mesa 3.

[0129] Figure 9 This is a schematic diagram of the structure before etching the second stage in Embodiment 1 of this application.

[0130] Step S105: As Figure 9As shown, with the help of overlay mark 5, the photolithography, mask deposition, dissolution and stripping, and dry etching processes in steps S103 to S104 are repeated. At this time, the pattern of the second mesa 3 with a side length of 380μm is photolithographically ...

[0131] Figure 10 This is a schematic diagram of the structure of the stepped double-mesa NV color center diamond scanning probe array prepared in Example 1 of this application.

[0132] Step S106: The NV color center diamond scanning probe array, together with the temporary support substrate 7, is placed in a tri-acid solution (perchloric acid: nitric acid: sulfuric acid patterning = patterning 1:1:1) and cleaned at 300°C for 4 hours to remove the UV-curable adhesive 6. At this time, the NV color center diamond scanning probe array is separated from the temporary support substrate 7, and an independent and clean NV color center diamond scanning probe array is obtained.

[0133] The NV color center diamond scanning probe array prepared in this embodiment is used to bond the second mesa 3 with UV-curable adhesive 6. During the scanning process, even if the probe is tilted within 5°, the first mesa 2 can still ensure that the waveguide structure 1 containing the color center is in effective contact with the sample to be tested, thus achieving stable nanoscale sensing and imaging.

[0134] The specific embodiments described above further illustrate the purpose, technical solution, and beneficial effects of this application. It should be understood that the above descriptions are merely specific embodiments of this application and are not intended to limit this application. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this application should be included within the protection scope of this application.

Claims

1. A stepped double-mesa diamond scanning probe with NV color centers, comprising a waveguide structure containing NV color centers, a first mesa, and a second mesa arranged in a stepped manner from top to bottom; in, The waveguide structure has a height of h1, the first platform has a height of h2, the step length of the first platform is l2, the second platform has a height of h3, and the step length of the second platform is l3. 。 2. The NV color center diamond scanning probe according to claim 1, wherein, The NV color center is located 2-50 nm below the surface of the waveguide structure; The waveguide structure containing the NV color center is cylindrical, parabolic, or frustum-shaped. 100nm≤h1≤2μm.

3. The NV color center diamond scanning probe according to claim 1, wherein, The shapes of the first and second countertops are each independently selected from any one of a square, rectangle, or circle; The side length or diameter of the first platform is a1, 1≤a1≤100μm, and the side length or diameter of the second platform is a2, 50≤a2≤600μm, a1<a2.

4. The NV color center diamond scanning probe according to claim 1, wherein, The NV color center diamond scanning probe has a scanning angle tolerance of no more than 10° during operation.

5. The NV color center diamond scanning probe according to claim 1, wherein, The first platform is suitable for adapting to the tilt angle of the sample during scanning, and the second platform is suitable for assembly and fixation.

6. A method for preparing an NV color center diamond scanning probe as described in any one of claims 1-5, comprising: Provide diamond substrate; A waveguide structure including at least one NV color center is formed in a first region of the diamond substrate; A first patterning process is performed on the surface of the diamond substrate on which the waveguide structure is formed to form a first mask layer, the first mask layer covering a predetermined area of ​​the waveguide structure and the first mesa; Using the first mask layer as a cover, the diamond substrate is etched for the first time to form the first mesa; The first mesa of the diamond substrate is fixed to the temporary support substrate; A second patterning process is performed on the surface of the diamond substrate facing away from the first mesa to form a second mask layer, which corresponds to a predetermined second mesa region. Using the second mask layer as a cover, the diamond substrate is etched a second time to form the second mesa; Remove the remaining mask layer and peel the first mesa from the temporary support substrate to obtain the stepped double-mesa NV color center diamond scanning probe.

7. The preparation method according to claim 6, wherein, In the step of forming a waveguide structure including at least one NV color center in a first region of the diamond substrate, an NV color center precursor is formed by nitrogen ion implantation, and then the NV color center precursor is annealed to obtain the NV color center; wherein... The implantation dose in the nitrogen ion implantation treatment is 1×10⁻⁶. 10 ~1×10 14 ions / cm 2 The injection energy is 1~40keV, and the NV color center precursor is located 2~50nm below the surface of the diamond substrate; In the annealing process, the annealing temperature is 800~1200℃, the annealing time is 2~6h, and the annealing atmosphere is a vacuum or inert atmosphere. Under the condition that the annealing atmosphere is a vacuum, the vacuum level is not less than 1×10⁻⁶. -5 Pa; Under the condition that the annealing atmosphere is an inert atmosphere, the purity of the inert gas is not less than 99%.

8. The preparation method according to claim 6 further includes, after forming a waveguide structure including at least one NV color center in the first region of the diamond substrate, forming overlay marks for photolithography alignment on the diamond substrate.

9. The preparation method according to claim 8, wherein, The first patterning process includes: spin-coating photoresist onto the surface of a diamond substrate on which the waveguide structure is formed to cover the waveguide structure; determining the area of ​​the first mesa by overlay marking and performing a first exposure process; depositing metal material in the area of ​​the first mesa after the first exposure process; removing the photoresist and the metal material deposited on the photoresist; and forming a first mask layer with the metal deposited in the remaining area of ​​the first mesa. The second patterning process includes: spin-coating photoresist on the surface of a diamond substrate facing away from the first mesa, determining the area of ​​the second mesa by overlay marking and performing a second exposure process, depositing metal material in the area of ​​the second mesa after the second exposure process, removing the photoresist and the metal material deposited on the photoresist, and the remaining metal deposited in the area of ​​the second mesa forms a second mask layer.

10. The preparation method according to claim 6, further comprising: After the first mesa is peeled off from the temporary support substrate, the NV color center diamond scanning probe is acid-washed in a solution consisting of a combination of perchloric acid, nitric acid, and sulfuric acid.

Images