An integrated microwave antenna composite electrode structure for NV color center quantum sensing and a preparation method thereof

Abstract

The application discloses an integrated microwave antenna composite electrode structure for NV color center quantum sensing and a preparation method thereof, and belongs to the technical fields of quantum sensor devices, microwave antenna integration and micro-nano processing technology, and comprises a diamond substrate, an NV color center layer, an SiO2 / Al2O3 composite transition layer and a Ti / Cr-Pt-Au composite metal electrode layer; the composite metal electrode layer comprises an omega-shaped antenna main body area and a feeding / contact area, the omega-shaped antenna main body area is provided with an optical window / microwave coupling area and an open slot, and the omega-shaped antenna main body area is configured to form a first resonant response and a second resonant response. According to the application, the omega-shaped microwave antenna is directly integrated on the surface of the diamond substrate in the form of the composite metal electrode layer, the assembly gap and the repeated positioning error between the external antenna and the diamond are reduced, and the microwave coupling stability is improved.

Description

Technical Field

[0001] This invention relates to the fields of quantum sensor devices, microwave antenna integration and micro / nano fabrication technology, specifically to an integrated microwave antenna composite electrode structure for NV color center quantum sensing and its fabrication method. Background Technology

[0002] Diamond NV centers are solid-state quantum defects formed by substituted nitrogen atoms and adjacent vacancies in the diamond lattice. They can be optically polarized, microwave-controlled, and fluorescence readout at room temperature. Their spin energy levels exhibit responsiveness to external physical quantities such as magnetic fields, current-induced magnetic fields, temperature, and stress. In continuous-wave optically probed magnetic resonance (ODMR) measurements, lasers are used to initialize and read out the NV electron spin states, while microwave signals are used to drive electron spin level transitions. Whether the microwave excitation structure can form a stable, effective, and reasonably distributed microwave field in the sensitive region of the NV center directly affects the contrast, linewidth, baseline stability, and accuracy of subsequent physical quantity inversion in the ODMR spectrum.

[0003] In existing diamond NV center sensing systems, microwave excitation is typically provided by a PCB microstrip antenna, an external metal coil, a coplanar waveguide, or a discrete microwave radiator. There are minute air gaps and assembly deviations between the diamond and the microwave antenna, and changes in their relative position and orientation occur after repeated disassembly and reassembly or long-term operation. When the microwave field distribution or coupling distance changes, the effective microwave excitation received by the NV center fluctuates, leading to a decrease in ODMR spectral contrast, spectral broadening, enhanced baseline undulation, or increased dispersion of multiple measurement results, ultimately affecting the stability of magnetic field and current measurement results. Summary of the Invention

[0004] In view of the above-mentioned problems, the present invention provides an integrated microwave antenna composite electrode structure for NV color center quantum sensing and its fabrication method.

[0005] Therefore, the technical problem solved by this invention is: how to solve the problems of assembly gaps and repetitive positioning errors between the external microwave antenna and the diamond in the existing diamond NV center sensing system, the drift of microwave coupling state, resulting in fluctuations in the effective microwave excitation received by the NV center, a decrease in ODMR spectral contrast, and insufficient measurement stability.

[0006] To solve the above-mentioned technical problems, the present invention provides the following technical solution: an integrated microwave antenna composite electrode structure for NV color center quantum sensing, comprising, The diamond substrate, the composite transition layer formed on the surface of the diamond substrate, the composite metal electrode layer formed on the surface of the composite transition layer, and the NV color center layer, wherein the NV color center layer is disposed in the near-surface region of the diamond substrate near the composite transition layer. The composite metal electrode layer includes an Ω-shaped antenna body region and a feed / contact region that are electrically connected to each other; the Ω-shaped antenna body region is provided with an optical window / microwave coupling region and an opening slot that are interconnected, and the opening slot extends from the optical window / microwave coupling region toward the feed / contact region; The optical window / microwave coupling region is used to allow laser light to be incident on the region where the NV color center layer is located, and to allow the microwave field to form a coupled excitation in the region where the NV color center layer is located.

[0007] As a preferred embodiment of the integrated microwave antenna composite electrode structure for NV color center quantum sensing described in this invention, the composite transition layer includes a SiO2 anti-reflection layer and an Al2O3 interface enhancement layer. The SiO2 anti-reflection layer is located on the surface of the diamond substrate, and the Al2O3 interface enhancement layer is located between the SiO2 anti-reflection layer and the composite metal electrode layer.

[0008] As a preferred embodiment of the integrated microwave antenna composite electrode structure for NV color center quantum sensing described in this invention, the composite metal electrode layer sequentially comprises a Ti / Cr adhesion layer, a Pt blocking / stabilizing layer, and an Au main microwave metal electrode layer along the direction away from the diamond substrate.

[0009] As a preferred embodiment of the integrated microwave antenna composite electrode structure for NV color center quantum sensing described in this invention, the optical window / microwave coupling region is a circular opening; a bottom retention gap is provided between the end of the opening slot away from the optical window / microwave coupling region and the feeding / contact area.

[0010] As a preferred embodiment of the integrated microwave antenna composite electrode structure for NV color center quantum sensing described in this invention, wherein: the feeding / contact area is used for electrical connection with an external microwave feeding terminal; The Ω-shaped antenna body region is configured to form a first resonant response and a second resonant response, the first resonant response being used to provide microwave excitation to the NV color center layer at a frequency of 2.87 GHz, and the second resonant response having a resonant frequency of 3.149 GHz.

[0011] As a preferred embodiment of the integrated microwave antenna composite electrode structure for NV color center quantum sensing described in this invention, the diamond substrate has a length of 5.0 mm, a width of 5.0 mm, and a thickness of 0.4 mm; the radius of the circular opening is 0.6 mm, the width of the opening groove is 0.2 mm, the effective length of the opening groove from the edge of the circular opening along the extending direction to the end is 1.2 mm, and the bottom retaining gap is 0.1 mm.

[0012] As a preferred embodiment of the integrated microwave antenna composite electrode structure for NV color center quantum sensing described in this invention, the thickness of the Ti / Cr adhesion layer is 10 nm, the thickness of the Pt blocking / stabilizing layer is 50 nm, and the thickness of the Au main microwave metal electrode layer is 200 nm.

[0013] This invention provides a method for fabricating an integrated microwave antenna composite electrode structure for NV color center quantum sensing.

[0014] To solve the above-mentioned technical problems, the present invention provides the following technical solution: a method for fabricating an integrated microwave antenna composite electrode structure for NV color center quantum sensing, comprising: A diamond substrate containing an NV color center layer is provided, and the diamond substrate is cleaned, dried and surface activated. A SiO2 anti-reflection layer and an Al2O3 interface reinforcement layer are sequentially formed on the surface of the diamond substrate to obtain a composite transition layer. Photoresist is spin-coated onto the surface of the composite transition layer, and then aligned and exposed under an exposure beam using a mask with an Ω-shaped pattern. The exposed photoresist is developed to form a patterned window corresponding to the main area of ​​the Ω-shaped antenna. A composite metal deposition layer is formed by sequentially depositing a Ti / Cr adhesion layer, a Pt barrier / stabilizing layer, and an Au main microwave metal electrode layer on the graphic window and the photoresist surface. The photoresist and the portion of the composite metal deposition layer covering the photoresist surface are removed by a stripping process, while the portion of the composite metal deposition layer located within the pattern window is retained, and the retained portion forms the composite metal electrode layer.

[0015] As a preferred embodiment of the preparation method of the integrated microwave antenna composite electrode structure for NV color center quantum sensing described in this invention, the cleaning includes acetone cleaning, isopropanol cleaning and deionized water cleaning, and the surface activation treatment includes oxygen plasma treatment or ultraviolet ozone treatment. The sidewalls of the graphic window formed after development have an inward-shrinking morphology.

[0016] As a preferred embodiment of the method for fabricating an integrated microwave antenna composite electrode structure for NV color center quantum sensing according to the present invention, the patterned window is subjected to oxygen plasma debinding treatment after the patterned window is formed and before the Ti / Cr adhesion layer is deposited; after the diamond substrate subjected to oxygen plasma debinding treatment enters the metal deposition cavity, the patterned window is subjected to in-situ argon ion cleaning. The Ti / Cr adhesion layer, the Pt barrier / stabilizing layer, and the Au main microwave metal electrode layer are sequentially deposited using a multi-target continuous magnetron sputtering method without breaking the vacuum.

[0017] The beneficial effects of the present invention are as follows: The present invention directly forms an Ω-shaped microwave antenna on the surface of a diamond substrate in the form of a composite metal electrode layer. There is no air gap between the microwave excitation source and the NV color center layer. The relative position and orientation of the two do not change with repeated disassembly and assembly, which reduces the assembly gap and repeated positioning error between the external antenna and the diamond, and improves the microwave coupling stability. This invention employs a SiO2 / Al2O3 composite transition layer and a Ti / Cr-Pt-Au composite metal electrode layer. The SiO2 anti-reflection layer improves the optical reflection conditions of the diamond substrate surface, while the Al2O3 interface reinforcement layer enhances the compactness of the composite transition layer and the interfacial bonding stability between it and the composite metal electrode layer. The Ti / Cr adhesion layer, Pt blocking / stabilizing layer, and Au main microwave metal electrode layer respectively perform the functions of adhesion, blocking, and conductivity, thereby improving the adhesion reliability, thermal stability, and microwave conductivity of the metal electrodes on the diamond surface. This invention preserves the optical window / microwave coupling area and opening slot in the main body area of ​​the Ω-shaped antenna, so that the laser incident and fluorescence collection paths are not blocked by the metal layer and the microwave current path remains continuous, enabling laser incident, fluorescence collection and microwave excitation to be achieved synergistically on the same chip surface. This invention, through defined size parameters, dual-resonance response, and 25-point magnetic field uniformity simulation, provides an engineering basis for the designable, verifiable, and reproducible fabrication of an integrated microwave antenna composite electrode structure for NV center quantum sensing. It is applicable to diamond NV center magnetic field measurement, quantum current sensing, and miniaturized ODMR readout systems. Attached Figure Description

[0018] To more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0019] Figure 1 This is a top view schematic diagram of an integrated microwave antenna composite electrode structure for NV color center quantum sensing, provided as an embodiment of the present invention.

[0020] Figure 2 This is a cross-sectional schematic diagram of an integrated microwave antenna composite electrode structure for NV color center quantum sensing, provided as an embodiment of the present invention.

[0021] Figure 3This is a schematic diagram illustrating the fabrication process of an integrated microwave antenna composite electrode structure for NV color center quantum sensing, as provided in one embodiment of the present invention.

[0022] Figure 4 This is a schematic diagram of the Ω-shaped integrated microwave antenna dimensions in an integrated microwave antenna composite electrode structure for NV color center quantum sensing, provided as an embodiment of the present invention.

[0023] Figure 5 The image shows a simulation diagram of the magnetic field distribution and 25-point uniformity in an integrated microwave antenna composite electrode structure for NV color center quantum sensing, provided as an embodiment of the present invention.

[0024] Figure 6 The figure shows the simulation curve of the dual resonance of the Ω-shaped integrated microwave antenna in the composite electrode structure of the integrated microwave antenna for NV color center quantum sensing, which is provided as an embodiment of the present invention.

[0025] Figure reference numerals: 1—Diamond substrate; 2—NV color center layer; 3—Composite transition layer; 31—SiO2 antireflective layer; 32—Al2O3 interface enhancement layer; 4—Composite metal electrode layer; 41—Ti / Cr adhesion layer; 42—Pt blocking / stabilizing layer; 43—Au main microwave metal electrode layer; 5—Optical window / microwave coupling area; 6—Opening slot; 7—Ω-shaped antenna body area; 8—Feed / contact area; 9—Mask; 10—Photoresist; 11—Exposure beam; 12—Graphic window; 13—Composite metal deposition layer; 14—Magnetic field sampling point. Detailed Implementation

[0026] To make the present invention more apparent and understandable, the specific embodiments of the present invention will be described in detail below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort should fall within the protection scope of the present invention.

[0027] It should be noted that the terms "first," "second," etc., in the specification, claims, and accompanying drawings of this application are used only to distinguish similar objects and are not used to limit a specific order. The term "comprising" and its variations should be understood as an open-ended expression, that is, including but not limited to the listed technical features. The dimensional and thickness parameters involved in this embodiment are used to illustrate an implementable structure, and except for explicitly defined structural fit relationships, proportional adjustments under the same technical concept are not excluded.

[0028] Example 1, referring to Figure 1 , Figure 2 , Figures 4-6This is one embodiment of the present invention, which provides an integrated microwave antenna composite electrode structure for NV color center quantum sensing, comprising: The diamond substrate 1, the composite transition layer 3 formed on the surface of the diamond substrate 1, the composite metal electrode layer 4 formed on the surface of the composite transition layer 3, and the NV color center layer 2, wherein the NV color center layer 2 is disposed in the near-surface region of the diamond substrate 1 near the composite transition layer 3.

[0029] Specifically, refer to Figure 2 The diamond substrate 1 serves as the carrier of the entire structure, and has a length of 5.0 mm, a width of 5.0 mm, and a thickness of 0.4 mm. The near-surface region refers to the area on the diamond substrate 1 closest to the surface where the composite transition layer 3 is formed, defined by the formation process of the NV color center layer 2. In some embodiments, the NV color center layer 2 is formed by nitrogen ion implantation, high-temperature annealing, and acid etching of the diamond substrate 1; in other embodiments, the NV color center layer 2 is formed by in-situ doping during diamond growth.

[0030] Understandably, NV centers are solid-state quantum defects formed by substituted nitrogen atoms and adjacent vacancies in a diamond lattice. NV centers possess optical polarization, microwave manipulation, and fluorescence readout characteristics at room temperature. Their spin energy levels respond to external physical quantities such as magnetic fields, current-induced magnetic fields, temperature, and stress, thus making them widely used in quantum magnetic field measurement, quantum current sensing, chip-level electromagnetic field imaging, and miniaturized precision measurement systems. In continuous-wave optically probed magnetic resonance (ODMR) measurements, lasers are used to initialize and read out the NV electron spin states, microwave signals are used to drive electron spin level transitions, and external magnetic fields or magnetic fields generated by the measured current alter the position, splitting degree, and line shape characteristics of the ODMR spectral lines.

[0031] Reference Figure 1 The composite metal electrode layer 4 includes an Ω-shaped antenna body region 7 and a feed / contact region 8 that are electrically connected to each other. The Ω-shaped antenna body region 7 is provided with an optical window / microwave coupling region 5 and an opening slot 6 that are interconnected. The opening slot 6 extends from the optical window / microwave coupling region 5 toward the feed / contact region 8. The optical window / microwave coupling region 5 is used to allow laser light to be incident on the region where the NV color center layer 2 is located, and to allow the microwave field to form a coupled excitation in the region where the NV color center layer 2 is located.

[0032] Specifically, the optical window / microwave coupling area 5 is located in the middle of the Ω-shaped antenna body area 7. The opening slot 6 and the optical window / microwave coupling area 5 are connected to form the opening part of the Ω-shaped metal pattern. The feed / contact area 8 is used to introduce external microwave signals into the Ω-shaped antenna body area 7. The Ω-shaped antenna body area 7 and the feed / contact area 8 together form an Ω-shaped integrated microwave antenna.

[0033] Furthermore, the optical window / microwave coupling region 5 and the opening slot 6 retain laser incident and fluorescence collection channels within the Ω-shaped antenna body region 7, allowing the incident laser to enter the diamond substrate 1 through the optical window / microwave coupling region 5 and act on the NV color center layer 2. The fluorescence signal generated by the NV color center is collected and output through the optical window / microwave coupling region 5, and the laser incident and fluorescence collection paths are not blocked by the metal layer. At the same time, the Ω-shaped antenna body region 7 forms a continuous microwave current path on the surface of the diamond substrate 1. The microwave current path is not narrowed or discontinuous due to the retention of the optical channel, and microwave excitation and optical readout are thus achieved collaboratively on the same chip surface.

[0034] Since the composite metal electrode layer 4 is directly formed on the surface of the diamond substrate 1, there is no air gap between the microwave excitation source and the NV color center layer 2. The relative position and orientation of the two do not change with repeated disassembly and assembly. The effective microwave excitation received by the NV color center layer 2 remains stable, thereby reducing the influence of assembly gap and repeated positioning error on the microwave coupling state and improving microwave coupling stability.

[0035] Furthermore, the Ω-shaped integrated microwave antenna is directly constructed on the surface of the diamond substrate 1, without occupying the installation space of an external microwave antenna. This facilitates the simultaneous arrangement of functional channels for laser incident, fluorescence collection, microwave feeding, and electrical connection within a limited packaging space, reducing the overall size and assembly complexity of the sensor head. In quantum current sensing applications, the sensing unit can thus be arranged close to the conductor being measured, and the microwave near field can be stably and continuously concentrated in the region where the NV color center layer 2 is located.

[0036] Furthermore, referring to Figure 2 The composite transition layer 3 includes a SiO2 anti-reflection layer 31 and an Al2O3 interface enhancement layer 32. The SiO2 anti-reflection layer 31 is located on the surface of the diamond substrate 1, and the Al2O3 interface enhancement layer 32 is located between the SiO2 anti-reflection layer 31 and the composite metal electrode layer 4.

[0037] Specifically, the SiO2 antireflection layer 31 is used to improve the optical reflection conditions of the diamond substrate 1 surface, thereby reducing ineffective reflections during laser incident and fluorescence collection processes; the Al2O3 interface enhancement layer 32 is used to improve the compactness of the composite transition layer 3 and the interfacial bonding stability between the composite transition layer 3 and the composite metal electrode layer 4.

[0038] It is understandable that diamond is an insulating material with a dense surface structure, high chemical stability, and low surface energy. The composite transition layer 3 forms a metallization interface between the diamond substrate 1 and the composite metal electrode layer 4, providing an adhesion basis for the deposition of the composite metal electrode layer 4. This suppresses problems such as film edge warping, local cracks, pad peeling, or contact resistance drift that may occur during photolithography stripping, gold wire bonding, temperature cycling, and continuous microwave loading. This allows optical functions and electrode adhesion reliability to work synergistically in the layered structure.

[0039] Furthermore, referring to Figure 2 The composite metal electrode layer 4 includes, in sequence along the direction away from the diamond substrate 1, a Ti / Cr adhesion layer 41, a Pt blocking / stabilizing layer 42, and an Au main microwave metal electrode layer 43.

[0040] Specifically, the Ti / Cr adhesion layer 41 is used to enhance the adhesion strength between the composite metal electrode layer 4 and the composite transition layer 3; the Ti / Cr adhesion layer 41 refers to an independent Ti layer, an independent Cr layer, a Ti / Cr alloy layer, or a double-layer adhesion structure composed of Ti and Cr layers superimposed; both Ti and Cr have high interfacial activity, and the high interfacial activity of Ti or Cr is used to enhance the mechanical adhesion between the composite metal electrode layer 4 and the SiO2 / Al2O3 composite transition layer 3, preventing the metal electrode from warping or falling off during peeling processing, high-temperature thermal cycling, and microwave loading.

[0041] The Pt blocking / stabilizing layer 42 is used to suppress interlayer diffusion and improve the stability of the composite metal electrode layer 4 under thermal cycling and microwave loading conditions; the Au main microwave metal electrode layer 43 is used to form a microwave conductive channel and a surface reflective layer, and the Au main microwave metal electrode layer 43 constitutes the surface layer of the composite metal electrode layer 4. In some embodiments, the thickness of the Ti / Cr adhesion layer 41 is 10 nm, the thickness of the Pt blocking / stabilizing layer 42 is 50 nm, and the thickness of the Au main microwave metal electrode layer 43 is 200 nm.

[0042] It is understood that the three metal layers of the composite metal electrode layer 4 respectively perform the functions of adhesion, diffusion blocking, and conductivity: the Ti / Cr adhesion layer 41 provides bonding force at the interface, ensuring the integrity of the metal pattern boundary under the mechanical action of photolithography lift-off and subsequent power feeding connection; the Pt blocking / stabilizing layer 42 blocks the interlayer diffusion channel, preventing the electrical performance of the composite metal electrode layer 4 from drifting under thermal cycling and continuous microwave loading conditions; the Au main microwave metal electrode layer 43 provides a microwave current path and also participates in optical reflection in the form of a surface reflective layer. Therefore, the composite metal electrode layer 4 simultaneously possesses adhesion enhancement, diffusion blocking, microwave conductivity, and optical reflection functions, improving the adhesion reliability, thermal stability, and microwave conductivity performance of the diamond surface integrated microwave antenna.

[0043] Furthermore, referring to Figure 1 and Figure 4 The optical window / microwave coupling region 5 is a circular opening; a bottom retention gap is provided between the end of the opening slot 6 away from the optical window / microwave coupling region 5 and the feeding / contact region 8. In some embodiments, the optical window / microwave coupling region 5 may also be a near-circular opening.

[0044] Specifically, refer to Figure 4 The radius of the circular opening The width of the opening groove 6 is 0.6 mm. The Ω-shaped antenna body region 7 has a structural length parameter of 0.2 mm. The structural length parameter The bottom retains a gap of 1.9 mm. The effective length of the opening groove 6 from the edge of the circular opening along the extending direction to the end is 0.1 mm. From the structural length parameter The radius and the bottom retaining gap Together, we determine that the following equation is satisfied: (1) in, The effective length of the opening slot. For structural length parameters, Let be the radius of the circular opening. Leave a gap at the bottom. = 1.9 mm = 0.6 mm Substituting 0.1 mm into equation (1), the effective length of the opening groove 6 is obtained. It is 1.2 mm.

[0045] It is understandable that the radius of the circular opening... A central window is reserved for laser incidence and fluorescence collection; the width of the opening slot 6 Optical clearance and structural openings are provided without disrupting the continuity of the Ω-shaped metal current; the bottom retains a gap. Define the positional relationship between the opening slot 6 and the power supply / contact area 8.

[0046] Furthermore, to illustrate the coverage relationship of the Ω-shaped antenna body region 7 on the surface of the diamond substrate 1, the area of ​​the upper surface of the diamond substrate 1 is denoted as... The area of ​​a circular optical window is denoted as The area of ​​the open slot is denoted as The effective coverage area of ​​the Ω-shaped metal electrode can be estimated using the following formula: (2) in, The effective coverage area of ​​the Ω-shaped metal electrode and These are the length and width of the diamond substrate 1, respectively. Let be the radius of the circular opening. The width of the opening slot, Let be the effective length of the slot. Substituting the parameters, the effective coverage area of ​​the Ω-shaped metal electrode is 23.63 mm. 2 The results indicate that, while retaining the central optical window and the opening slot, the metal electrode covering a large area of ​​the diamond substrate 1 surface is beneficial for forming stable microwave near-field coupling and local optical reflection.

[0047] Furthermore, the feed / contact region 8 is used for electrical connection with an external microwave feed terminal; the Ω-shaped antenna body region 7 is configured to form a first resonant response and a second resonant response, the first resonant response being used to provide microwave excitation to the NV color center layer 2 at a frequency of 2.87 GHz, and the resonant frequency of the second resonant response being 3.149 GHz.

[0048] Specifically, the feed / contact area 8 is located on the side opposite to the end of the opening slot 6 across the bottom retaining gap, and is used to connect with an external microwave source, microstrip feed line, micro probe or gold wire to introduce a microwave signal with a target frequency of 2.87 GHz into the metal electrode path of the Ω-shaped antenna body area 7.

[0049] To verify the input matching characteristics of the Ω-shaped integrated microwave antenna near the NV color center ODMR target frequency band, the input reflection coefficient S of the Ω-shaped integrated microwave antenna was measured. 11 Parameter simulation, S 11S is the input port reflection coefficient in microwave scattering parameters, used to characterize the proportion of the input power at the feed port that is reflected. 11 The frequency range is 2.7–3.25 GHz, expressed in dB. (Refer to...) Figure 6 The Ω-shaped integrated microwave antenna forms a first resonant response near 2.87 GHz and a second resonant response at 3.149 GHz. The second resonant point is S... 11 The value is -10.9 dB. The first resonant response covers a frequency of 2.87 GHz, enabling the Ω-shaped integrated microwave antenna to provide microwave excitation to the NV color center layer 2 at a frequency of 2.87 GHz.

[0050] Furthermore, based on the input reflection coefficient and S 11 The conversion relationship between them, the port voltage reflection coefficient is calculated by the following formula: (3) in, Port voltage reflection coefficient, Let be the input reflection coefficient, expressed in dB. When When = -10.9 dB, It is 0.285. The port received power ratio is further expressed as: (4) in, This represents the percentage of power received at the port.

[0051] Equation (4) shows that the port received power ratio at the second resonant point is 91.9%. This result indicates that the main body region 7 of the Ω-shaped antenna has a high microwave power receiving capability at the second resonant point; at the same time, the first resonant response near 2.87 GHz corresponds to the ODMR microwave excitation requirement near the zero-field splitting frequency band of the diamond NV color center, thus ensuring the microwave power utilization rate.

[0052] Furthermore, the frequency of the first resonant response, 2.87 GHz, corresponds to the zero-field splitting frequency of the NV color center under zero magnetic field. During quantum sensing processes such as vector magnetometry and current sensing, an external bias magnetic field is applied to the NV color center layer 2 to distinguish energy levels along different crystal axes. At this time, the spin transition frequency of the NV color center shifts to a higher frequency region due to the Zeeman effect. The resonant frequency of the second resonant response, 3.149 GHz, is located within this high-frequency region, enabling the Ω-shaped integrated microwave antenna to maintain efficient microwave energy coupling in the high-frequency control mode under the applied external bias magnetic field. At the second resonant point, S... 11With a sensitivity of -10.9 dB and a port receive power ratio of 91.9%, the dynamic range of the sensor's magnetic field measurement is broadened. Thus, the first and second resonant responses together cover the zero-field excitation frequency and the high-frequency modulation range under the bias magnetic field of the NV center quantum sensor, constituting a dual-resonant design for NV center quantum sensing.

[0053] Furthermore, to verify the spatial distribution of the microwave field on the surface of the diamond substrate 1, a magnetic field distribution simulation was performed on the Ω-shaped integrated microwave antenna under 2.87 GHz microwave excitation conditions. (Refer to...) Figure 5 A 5×5 matrix sampling point array is set on the surface of the diamond substrate 1, with a total of 25 magnetic field sampling points 14. The 25 magnetic field sampling points 14 are distributed in the effective microwave coupling area of ​​the diamond substrate 1, and simultaneously cover the area around the optical window / microwave coupling area 5, the edge area of ​​the metal electrode, and the corner area of ​​the substrate.

[0054] Let the first Line number The magnetic field strength at each sampling point is , = 1,2,3,4,5 If the sample numbers are 1, 2, 3, 4, 5, then the average magnetic field strength at the sampling points is expressed as: (5) in, This represents the average magnetic field strength at 25 sampling points. For the first Line number The magnetic field strength at each sampling point is listed. The magnetic field uniformity index is calculated using the following formula: (6) in, As an indicator of magnetic field uniformity, The standard deviation of the magnetic field strength at 25 sampling points. This represents the average magnetic field strength at 25 sampling points.

[0055] Reference Figure 5 In (a), the Ω-shaped integrated microwave antenna forms a two-dimensional magnetic field distribution corresponding to the structural contour on the surface of the diamond substrate 1; refer to Figure 5 In Figure (b), the magnetic field intensity curves extracted along the center lines of the X and Y directions show that the magnetic field distribution changes with the profile of the Ω-shaped metal electrode and the central opening structure, forming a coupling region for microwave excitation of the NV color center around the optical window / microwave coupling region 5.

[0056] Furthermore, the maximum magnetic field strength at 25 sampling points The minimum value is 0.739 G. The gain is 0.294G, and the 25-point range uniformity calculated using the range method is 56.95%; the standard uniformity calculated based on 25 sampling points is 75.35%. This result indicates that the Ω-shaped integrated microwave antenna forms a relatively stable microwave magnetic field distribution on the surface of the diamond substrate 1, providing a near-field microwave environment for the ODMR excitation of the NV color center layer 2.

[0057] In summary, the integrated microwave antenna composite electrode structure for NV center quantum sensing described in this embodiment is suitable for diamond NV center magnetic field measurement, quantum current sensing, and miniaturized ODMR readout systems.

[0058] Example 2, refer to Figure 3 This is one embodiment of the present invention, which provides a method for fabricating an integrated microwave antenna composite electrode structure for NV color center quantum sensing, comprising: Step 1: Provide a diamond substrate 1 containing an NV color center layer 2, and perform cleaning, drying and surface activation treatment on the diamond substrate 1.

[0059] Specifically, a diamond substrate 1 with a length of 5.0 mm, a width of 5.0 mm, a thickness of 0.4 mm, and containing an NV color center layer 2 is provided. The diamond substrate 1 is sequentially cleaned with acetone, isopropanol, and deionized water, i.e., the cleaning includes acetone cleaning, isopropanol cleaning, and deionized water cleaning; after cleaning, it is dried with nitrogen and then dehydrated and baked. The cleaning removes organic residues and particulate contaminants from the surface of the diamond substrate 1.

[0060] Furthermore, the surface of the diamond substrate 1 is subjected to a surface activation treatment, which includes oxygen plasma treatment or ultraviolet ozone treatment. This surface activation treatment improves the surface activity of the diamond substrate 1 and enhances the deposition quality of the subsequent composite transition layer 3.

[0061] Step 2: A SiO2 anti-reflection layer 31 and an Al2O3 interface reinforcement layer 32 are sequentially formed on the surface of the diamond substrate 1 to obtain a composite transition layer 3.

[0062] Specifically, the SiO2 antireflective layer 31 is prepared by plasma-enhanced chemical vapor deposition, magnetron sputtering, or atomic layer deposition; the Al2O3 interface enhancement layer 32 is prepared by atomic layer deposition to obtain better density and thickness uniformity. The resulting composite transition layer 3 provides an adhesion basis for the subsequent deposition of the composite metal electrode layer 4.

[0063] Step 3, refer to Figure 3In (a) and (b), photoresist 10 is spin-coated on the surface of the composite transition layer 3, and the photoresist 10 is aligned and exposed under the action of an exposure beam 11 through a mask 9 with an Ω-shaped pattern.

[0064] Specifically, photoresist 10 is spin-coated onto the surface of the composite transition layer 3, and after soft baking, a mask 9 with an Ω-shaped pattern is aligned with the diamond substrate 1, and exposure is performed using an exposure beam 11. In some embodiments, the photoresist 10 is a photoresist suitable for lift-off molding.

[0065] Step 4, refer to Figure 3 In step (c), the exposed photoresist 10 is developed to form a pattern window 12 corresponding to the Ω-shaped antenna main body region 7.

[0066] Specifically, the patterned window 12 corresponds to the Ω-shaped integrated microwave antenna pattern. The sidewalls of the patterned window 12 have an inward-shrinking shape, meaning that the sidewalls of the patterned window 12 contract inwards. This inward-shrinking shape prevents the subsequently deposited metal film from forming a continuous coating on the sidewalls of the photoresist 10, reducing the difficulty of peeling off caused by continuous coating of the metal film on the photoresist sidewalls, and facilitating metal peeling and shaping after composite metal deposition.

[0067] Step 5, refer to Figure 3 In step (d), a Ti / Cr adhesion layer 41, a Pt blocking / stabilizing layer 42, and an Au main microwave metal electrode layer 43 are sequentially deposited on the surface of the graphic window 12 and the photoresist 10 to form a composite metal deposition layer 13.

[0068] Specifically, after the pattern window 12 is formed and before the Ti / Cr adhesion layer 41 is deposited, the pattern window 12 is first subjected to a short-time oxygen plasma desmearing treatment; after the diamond substrate 1, which has undergone the oxygen plasma desmearing treatment, enters the metal deposition chamber, the pattern window 12 is subjected to in-situ argon ion cleaning.

[0069] Furthermore, the Ti / Cr adhesion layer 41, the Pt barrier / stabilizing layer 42, and the Au main microwave metal electrode layer 43 are sequentially deposited using a multi-target continuous magnetron sputtering method under vacuum conditions.

[0070] The Ti / Cr adhesive layer 41 is an independent Ti layer, an independent Cr layer, a Ti / Cr alloy layer, or a double-layer adhesive structure composed of a Ti layer and a Cr layer superimposed on each other.

[0071] In some embodiments, the thickness of the Ti / Cr adhesion layer 41 is 10 nm, the thickness of the Pt barrier / stabilizing layer 42 is 50 nm, and the thickness of the Au main microwave metal electrode layer 43 is 200 nm. This continuous deposition method under vacuum-free conditions reduces interlayer oxidation and contamination, and improves the interfacial continuity of the composite metal electrode layer 4.

[0072] Step 6, refer to Figure 3 In step (e), the photoresist 10 and the portion of the composite metal deposition layer 13 covering the surface of the photoresist 10 are removed by a stripping process, while the portion of the composite metal deposition layer 13 located within the pattern window 12 is retained, and the retained portion forms the composite metal electrode layer 4.

[0073] Specifically, after deposition, the diamond substrate 1 with the composite metal deposition layer 13 is placed in a stripping solution, causing the photoresist 10 and the portion of the composite metal deposition layer 13 covering the surface of the photoresist 10 to detach, leaving only the composite metal deposition layer 13 in the area corresponding to the pattern window 12. The retained portion forms a composite metal electrode layer 4, which constitutes the Ω-shaped antenna body region 7 and the feed / contact region 8, thus forming an Ω-shaped integrated microwave antenna, thereby obtaining the integrated microwave antenna composite electrode structure for NV color center quantum sensing.

[0074] Furthermore, after step 6, the input reflection coefficient S of the Ω-shaped integrated microwave antenna is calculated. 11 Parameter simulation or testing, S 11 S is the input port reflection coefficient in microwave scattering parameters, used to characterize the proportion of the input power at the feed port that is reflected. 11 Expressed in dB, the simulation or test frequency range is 2.7~3.25 GHz; reference Figure 6 When the Ω-shaped integrated microwave antenna forms a first resonant response near 2.87 GHz and an S resonant response at 3.149 GHz, 11 When the second resonant response is -10.9 dB, the Ω-shaped integrated microwave antenna is determined to meet the dual-resonant design requirements for ODMR microwave excitation of diamond NV color centers. Meanwhile, referring to... Figure 5 A 5×5 matrix sampling point array was set on the surface of the diamond substrate 1. The magnetic field strength at 25 magnetic field sampling points 14 was simulated and calculated under 2.87 GHz microwave excitation conditions. The two-dimensional magnetic field distribution map and the magnetic field uniformity results at 25 points were obtained to evaluate the near-field microwave excitation effect of the Ω-shaped antenna main body region 7 on the NV color center layer 2.

[0075] The fabrication method described in this embodiment, through the determination of pattern size, dual resonance verification, and 25-point magnetic field uniformity evaluation, enables the integrated microwave antenna composite electrode structure for NV color center quantum sensing to have an engineering basis that is designable, verifiable, and reproducible, providing a process basis for the subsequent integration of microwave excitation structures for chip-level quantum sensor devices.

[0076] It should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and not to limit it. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the spirit and scope of the technical solutions of the present invention, and all such modifications or substitutions should be covered within the scope of the claims of the present invention.

Claims

1. An integrated microwave antenna composite electrode structure for NV color center quantum sensing, characterized in that, include: A diamond substrate (1), a composite transition layer (3) formed on the surface of the diamond substrate (1), a composite metal electrode layer (4) formed on the surface of the composite transition layer (3), and an NV color center layer (2), wherein the NV color center layer (2) is disposed in the near-surface region of the diamond substrate (1) near the composite transition layer (3); The composite metal electrode layer (4) includes an Ω-shaped antenna body region (7) and a feed / contact region (8) that are electrically connected to each other; the Ω-shaped antenna body region (7) is provided with an optical window / microwave coupling region (5) and an opening slot (6) that are interconnected, and the opening slot (6) extends from the optical window / microwave coupling region (5) toward the feed / contact region (8). The optical window / microwave coupling region (5) is used to allow laser light to be incident on the region where the NV color center layer (2) is located, and to allow the microwave field to form a coupling excitation in the region where the NV color center layer (2) is located.

2. The integrated microwave antenna composite electrode structure for NV color center quantum sensing as described in claim 1, characterized in that, The composite transition layer (3) includes a SiO2 anti-reflection layer (31) and an Al2O3 interface enhancement layer (32). The SiO2 anti-reflection layer (31) is located on the surface of the diamond substrate (1), and the Al2O3 interface enhancement layer (32) is located between the SiO2 anti-reflection layer (31) and the composite metal electrode layer (4).

3. The integrated microwave antenna composite electrode structure for NV color center quantum sensing as described in claim 2, characterized in that, The composite metal electrode layer (4) includes, in sequence, a Ti / Cr adhesion layer (41), a Pt blocking / stabilizing layer (42), and an Au main microwave metal electrode layer (43) in the direction away from the diamond substrate (1).

4. The integrated microwave antenna composite electrode structure for NV color center quantum sensing as described in claim 3, characterized in that, The optical window / microwave coupling area (5) is a circular opening; a bottom retention gap is provided between the end of the opening groove (6) away from the optical window / microwave coupling area (5) and the power supply / contact area (8).

5. The integrated microwave antenna composite electrode structure for NV color center quantum sensing as described in claim 4, characterized in that, The feed / contact area (8) is used for electrical connection with an external microwave feed terminal; The Ω-shaped antenna body region (7) is configured to form a first resonant response and a second resonant response, the first resonant response being used to provide microwave excitation to the NV color center layer (2) at a frequency of 2.87 GHz, and the second resonant response having a resonant frequency of 3.149 GHz.

6. The integrated microwave antenna composite electrode structure for NV color center quantum sensing as described in claim 5, characterized in that, The diamond substrate (1) has a length of 5.0 mm, a width of 5.0 mm, and a thickness of 0.4 mm; the radius of the circular opening is 0.6 mm; the width of the opening groove (6) is 0.2 mm; the effective length of the opening groove (6) from the edge of the circular opening along the extension direction to the end is 1.2 mm; and the bottom retaining gap is 0.1 mm.

7. The integrated microwave antenna composite electrode structure for NV color center quantum sensing as described in claim 6, characterized in that, The thickness of the Ti / Cr adhesion layer (41) is 10 nm, the thickness of the Pt blocking / stabilizing layer (42) is 50 nm, and the thickness of the Au main microwave metal electrode layer (43) is 200 nm.

8. A method for fabricating an integrated microwave antenna composite electrode structure for NV color center quantum sensing, using the integrated microwave antenna composite electrode structure for NV color center quantum sensing as described in any one of claims 1 to 7, characterized in that, include: A diamond substrate (1) containing an NV color center layer (2) is provided, and the diamond substrate (1) is cleaned, dried and surface activated. A SiO2 antireflective layer (31) and an Al2O3 interface reinforcement layer (32) are sequentially formed on the surface of the diamond substrate (1) to obtain a composite transition layer (3). Photoresist (10) is spin-coated on the surface of the composite transition layer (3), and the photoresist (10) is aligned and exposed under the action of an exposure beam (11) through a mask (9) with an Ω-shaped pattern. The exposed photoresist (10) is developed to form a pattern window (12) corresponding to the main body area (7) of the Ω-shaped antenna. A Ti / Cr adhesion layer (41), a Pt barrier / stabilizing layer (42) and an Au main microwave metal electrode layer (43) are sequentially deposited on the surface of the pattern window (12) and the photoresist (10) to form a composite metal deposition layer (13). The photoresist (10) and the portion of the composite metal deposition layer (13) covering the surface of the photoresist (10) are removed by a stripping process, while the portion of the composite metal deposition layer (13) located within the graphic window (12) is retained, and the retained portion forms the composite metal electrode layer (4).

9. The method for fabricating an integrated microwave antenna composite electrode structure for NV color center quantum sensing as described in claim 8, characterized in that, The cleaning includes acetone cleaning, isopropanol cleaning and deionized water cleaning, and the surface activation treatment includes oxygen plasma treatment or ultraviolet ozone treatment. The sidewalls of the graphic window (12) formed after development have an inward-shrinking morphology.

10. The method for fabricating an integrated microwave antenna composite electrode structure for NV color center quantum sensing as described in claim 9, characterized in that, After the pattern window (12) is formed and before the Ti / Cr adhesion layer (41) is deposited, the pattern window (12) is subjected to oxygen plasma degumming treatment; after the diamond substrate (1) after oxygen plasma degumming treatment enters the metal deposition chamber, the pattern window (12) is subjected to argon ion in-situ cleaning. The Ti / Cr adhesion layer (41), the Pt barrier / stabilizing layer (42), and the Au main microwave metal electrode layer (43) are sequentially deposited using a multi-target continuous magnetron sputtering method under vacuum conditions.

Images