High-resolution magnetic imaging system and method with diamond microstructures

Abstract

A method for performing wide-field microscopy (WFM) using nitrogen vacancy (NV) centers in diamond. A diamond micro chip (DMC) having a (111)-oriented NV ensemble is temporarily adhered to a polymer microstructure on a portion of a transparent substrate, positioned above a placement location on a sample, and the transparent substrate tilted until the DMC detaches from the polymer microstructure and lands in the vicinity of the placement location, and then optionally its position is fined tuned. An image of the sample is then procured using NV WFM through the DMC.

Description

[0001] HIGH-RESOLUTION MAGNETIC IMAGING SYSTEM AND METHOD WITH DIAMOND

[0002] MICROSTRUCTURES

[0003] STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH

[0004] This invention was made with government support under Grant Number 2203829, awarded by the National Science Foundation (NSF) and by NSF through the University of Delaware Materials Research Science and Engineering Center DMR-2011824 Seed Award program. The government has certain rights in the invention.

[0005] CROSS-REFERENCE TO RELATED APPLICATIONS

[0006] This application claims priority from U.S. Provisional Application Ser. No. 63 / 518,567, titled “HIGH-RESOLUTION MAGNETIC IMAGING SYSTEM AND METHOD WITH DIAMOND MICROSTRUCTURES,” filed August 10. 2023, incorporated herein by reference.

[0007] BACKGROUND OF THE INVENTION

[0008] Quantum sensing with nitrogen vacancy (NV) centers in diamond is recognized as a quantum technology with potential for high-impact applications in the immediate horizon for microscopy of electrical current, magnetization, and spins in a wide range of systems. The outstanding feature that underscores NV’s utility is the ability to sense minute magnetic field at small scale, owing to its atomic size. Hence, NV enables microscopy of electric current, magnetization, and spins down to the sub-micron regime, which provides a means to meet the increasing demands for probing systems on the ever- smaller scale. Consequentially, NV enables sensing applications for a wide-range of disciplines, ranging from condensed matter and material science, to chemistry, biomedical science, geology, and circuit diagnosis.

[0009] However, efficient NV-sample integration with a high-quality interface, which is desirable for high- resolution and high-throughput microscopy, remains an outstanding challenge, hindering the wider application of NV quantum sensors.

[0010] One way to implement NV magnetic field imaging is via scanning probe microscopy (SPM). With NV-SPM, spatial-resolution is limited only by the stand-off distance d between the NV and the sample. This enables resolution as small as tens of nanometers. However, SPM necessarily involves slow pixel-by-pixel scanning, has been reported to sometimes scratch the sample, and is generally not suitable for liquid or soft matter samples. Furthermore, NV-SPM is associated with significant cost and complexity, such as for example, the ease at which an NV-SPM probe may lose its functionality (e.g. probe picking up dirt or the single NV trapped in the wrong charge state) and the need for high degree of vibration isolation and temperature stability.

[0011] Another implementation of NV magnetic field imaging is NV wide-field microscopy (WFM), using an NV wide-field apparatus as depicted in FIG. 1. Here, an NV ensemble (a group of a plurality of NVs) disposed in a thin layer across the diamond crystal is utilized. Each NV serves as a local magnetic field sensor, and with a suitable application of microwave (MW) fields to drive the NV spin transitions, the information of the magnetic field each NV detects is encoded in the emitted photoluminescence (PL). A camera captures PL images from the NV ensemble, from which an image of magnetic field can then be obtained. NV-WFM features parallel acquisition of magnetic field across an entire field-of-view and the absence of scanning, which enables high-throughput microscopy of both solid and liquid / soft samples. Spatial resolution as small as o~150 nm, limited by optical diffraction, can be achieved. While this does not reach what can be accomplished with NV-SPM, nevertheless a sub-pm resolution suffices for a large number of applications; additionally, there is room for further improvement, e.g. via inhomogeneous ensemble control and machine learning. Given the aforementioned features, NV-WFM provides a powerful means for high-throughput, high-resolution microscopy of magnetic field suitable for a wide-range of samples, with applications having been demonstrated in condensed matter science, chemistry, biology, geology, and device science.

[0012] A small stand-off distance d « o is desirable to achieve a resolution a that is diffraction-limited (~100s nm). NVs at a depth of tens of nm can be created reliably without significant detriment to their properties, and hence d is primarily determined by how well the diamond contacts the sample. However, creating a high-quality diamond-sample interface remains an outstanding challenge that hinders the wider application of NV-WFM. Depositing the sample material or fabricating the target device directly on diamond can ensure close proximity between the NVs and the sample, but this approach is possible only for a limited number of materials, e.g. for van der Waals materials which can be placed on diamond via exfoliation or polymer-based transfer, or for materials that can be grown on diamond, e.g. by evaporation or sputtering. When working with materials for which this option is not available, the diamond-sample interface has been created in the past by simply placing a bulk diamond crystal, typically ~mm in dimension, on the sample. However, such a large contact area necessarily has non-uniform flatness, and particles (e.g. dust) invariably get trapped in between the diamond and the sample, leading to a large and inhomogeneous cl that limits the resolution to no better than a few pm. Furthermore, imaging through diamond, which has a high index of refraction, leads to aberrations that can further degrade resolution.

[0013] Fabrication of a small and thin diamond structure to ensure a good diamond-sample interface has been applied in a diamond nanobeam application for singlepoint measurement. Diamond micro-chips (DMCs) with a lateral dimension ranging from hundreds to tens of pm and thicknesses less than few pm have been fabricated in the context of quantum optics. Such chips have also recently been employed for sensing applications in the context of condensed matter science and circuit analysis. However, key aspects critical to enabling broad application of DMCs for NV-WFM remain to be addressed.

[0014] First, it is generally expected that the process involved in fabrication, especially etching, has the potential to degrade spin coherence properties of NVs. In particular, inhomogeneous strain can be potentially introduced by the fabrication process and is detrimental to magnetic microscopy. A good spin coherence and benign strain profile (ideally similar to that of bulk diamond) are desirable. Second, while a small thickness is expected to reduce aberration when imaging through diamond, a diffractionlimited sub-pm resolution remains had not previously been demonstrated with NV-WFM on DMC. Thirdly, in the vast majority of NV-WFM applications, and in all the existing instances of DMC sensing, the external bias field and the measured component of stray field are along the NV axis at an angle with respect to the vertical; however, it is often desirable that a strictly vertical bias is applied, and the vertical stray field is measured. Lastly, it is desired to develop a reliable, deterministic placement technique that can position a diamond structure with lateral dimension in the tens of pm on the sample of interest.

[0015] While one group of researchers has demonstrated a dry-transfer technique to place a DMC 50 pm in dimension on van der Waals (vdW) material, there is still room for improvement. See, Ghiasi et al., Nitrogen-Vacancy Magnetometry of CrSBr by Diamond Membrane Transfer, npj 2D Mater Appl 7 , 62 (2023). (hereinafter, “Ghiasi”), incorporated herein by reference for all purposes. As described by Ghiasi, a DMC having dimensions of 50 x 50 x 5 pm3is detached from a platform by a sharp tip controlled by micromanipulators. After the detachment, the DMC drops on a polydimethylsiloxane (PDMS) layer that is held on a substrate (referred to as “PDMS 1”). A PMMA-PDMS stamp, comprising a layer of PDMS (referred to as “PDMS 2”) attached to a glass slide and coupled to a layer of PMMA, is brought in contact with the DMC by a micro-manipulator. The DMC adheres to the PMMA, allowing the DMC to be picked up by the PMMA-PDMS stamp. The DMC is transferred in contact with a target located in an imaging location on a SiO2 substrate. The PMMA is melted by heating to 180 °C, causing the PMMA to release from the PDMS attached to the slide such that the PMMA and DMC remain on the target. The PMMA membrane is then removed by e-beam lithography at the region of interest.

[0016] SUMMARY OF THE INVENTION

[0017] One aspect of the invention relates to a method for performing wide-field microscopy (WFM) using nitrogen vacancy (NV) centers in diamond. The method includes the steps of: providing a wide-field microscopy (WFM) apparatus, providing a sample to be studied with the WFM apparatus, and providing a diamond micro chip (DMC) having a (111)-oriented NV ensemble having an area. A transparent substrate having a polymer microstructure on a portion of one surface thereof covering an area less than the area of the DMC is then used for contacting the DMC with the polymer microstructure on the transparent substrate, causing the DMC to temporarily adhere to the polymer microstructure. The transparent substrate and DMC adhered to the polymer microstructure then approaches a position vertically above a placement location for of the DMC, and the transparent substrate is tilted until the DMC detaches from the polymer microstructure and lands in a position in a vicinity of the placement location. The step of providing the transparent substrate may include providing the transparent substrate on a tiltable, 3D translational stage controlled by a micropositioner. If the landing position of the DMC is unacceptable, the position of the DMC is fine tuned into an acceptable position relative to the placement location, such as using a sharp tip of a micropositioner. An image of the sample is then procured using NV WFM through the DMC.

[0018] The imaging may comprise performing strain microscopy or performing microscopy of electrical current, magnetization, or spin relating to the sample. In embodiments, the DMC has a thickness of ~1-2 m and may have a square geometry with a lateral dimension in the range of 10 - 50 pm. The DMC may optimally have a variation of Mz below 1 MHz with standard deviations corresponding to a fractional strain in a range of 1x10-6 - 3x106.

[0019] The sample, the polymer microstructure, the DMC, or a combination thereof may be viewed through an objective of the WFM apparatus while performing at least portions of steps of providing, picking up, and / or placing the DMC on the sample. The step of providing the DMC may include providing an array of DMCs and detaching a selected one of the DMCs from the array. The step of detaching the selected one of the DMCs may include causing the DMC to fall onto an intermediate substrate, and then picking up the DMC from the intermediate substrate using the transparent substrate with the polymer microstructure.

[0020] In embodiments, the array of DMCs may comprise a plurality of DMCs each attached to an array substrate by a bridge connecting an edge of each DMC to an edge of the array substrate, and the method may include detaching a selected one of the DMCs from the array comprises using a sharp tip to break off the chip from the array. In such embodiments, the bridge connecting the edge of each DMC to the array is off-center relative to a lateral centerline of the DMC intersecting the connecting edge, wherein breaking off the DMC from the array leaves a stub on the edge of the DMC, so that an orientation of a stub on the edge of the DMC can be viewed through the objective of the WFM apparatus to confirm that a desired face of the DMC is facing the objective.

[0021] The DMCs used in accordance with the exemplary methods as described herein are reusable - the same DMC may be used for performing the foregoing method steps fon a first sample, then removed from the first sample, and used for performing the method on at least a second sample.

[0022] In an embodiment, the sample comprises a microfluidic channel, wherein the DMC is deposited on a first surface of a base transparent substrate and a microfluidic channel is built on top of the front side of the base transparent substrate. In embodiments in which the base transparent substrate has first and second opposite sides and a first surface of the base transparent substrate is disposed on the first side, exciting and detecting the NV ensemble of the DMC may be performed from the second side of the base transparent substrate.

[0023] In embodiments, the transparent substrate has no polymer adhesion layer and has not undergone plasma treatment or annealing in the portion of the slide where the polymer is disposed prior to the polymer being disposed on the slide. In embodiments, the sample to be studied may be the DMC, and the procured image of the sample is used for localizing a nuclear recoil track within the DMC.

[0024] BRIEF DESCRIPTION OF THE DRAWINGS

[0025] FIG. 1 is a schematic drawing of an exemplary NV- WFM apparatus.

[0026] FIG. 2 is a schematic drawing of an exemplary DMC disposed on a sample on an exemplary NV-WFM apparatus.

[0027] FIGS. 3A-3E are schematic drawings illustrating an exemplary method for placement of a DMC in a sample location. FIGS. 3F-3L are photographic images illustrating the exemplary method for placement of a DMC in a first sample location.

[0028] FIG. 3M is a photographic image illustrating recycling of the DMC shown in FIGS. 3F-3L onto a second sample location.

[0029] FIG. 4A is a schematic cross-sectional view of a method for detaching a DMC onto a substrate.

[0030] FIG. 4B is a photographic image showing a DMC after separation from an array, showing part of a bridge optically visible.

[0031] FIGS. 4C and 4D are schematic figures depicting a method for bulk preparation of DMCs for use in applications as described herein.

[0032] FIGS. 5A and 5B illustrate Mzprofiles of two exemplary DMCs.

[0033] FIGS. 5C and 5D illustrate histograms of Mzgenerated from the DMCs shown in FIGS. 5A and 5B, respectively.

[0034] FIG. 6A is a graph showing exemplary optically detected magnetic resonance of (111)-oriented NVs in a DMC.

[0035] FIGS. 6B1 and 6B2 show Ramsey interferometry measurements of dephasing time, with 6B1 showing the Ramsey pulse sequence (laser, MW, and readout signals), and 6B2 showing a graph of the resulting measurements obtained.

[0036] FIGS. 6C1 and 6C2 show Hahn spin-echo measurements, with 6C1 showing the laser, MW, and readout signals, and 6C2 showing a graph of measurements obtained.

[0037] FIGS. 6D1 and 6D2 depict a relaxometry measurement obtaining a longitudinal relaxation time with 6D1 showing the laser, MW, and readout signals, and 6D2 showing a graph of measurements obtained.

[0038] FIG. 7A is a photographic image showing exemplary placement of a DMC on a fabricated wire.

[0039] FIG. 7B depicts a Simulated stray-field Bz.

[0040] Fig. 7C depicts a measured magnetic field map measured with current in the wire network.

[0041] Fig. 7D1 depicts localized strain features in a DMC that allow benchmarking of optical resolution, showing two localized strain features near each other.

[0042] Fig.7D2 depicts a linecut of selected data along a dashed line shown in FIG. 7D1.

[0043] FIGS. 8A-8C schematically illustrate an exemplary WIMP detection technique. FIG. 9 schematically illustrates an exemplary microfluidics device built over a DMC as described herein.

[0044] DETAILED DESCRIPTION OF THE INVENTION

[0045] Use of a diamond micro-chip (DMC) in NV-WFM provides a high-quality interface with an arbitrary solid-state sample. In embodiments, the NVs may also interface with liquid-phase materials via microfluidics. Other embodiments include methods for attaching a DMC to a transparent substrate, and subsequently creating a microfluidics device on top of the substrate, as described in more detail below with respect to FIG. 9. This approach enables integration of NVs with microfluidics that utilize well-established fabrication procedures, instead of requiring interfacing microfluidics with bulk diamond, which has a more complex fabrication process.

[0046] Characterization of a diamond micro-chips (DMC) containing a (111)- oriented NV ensemble, as discussed herein, demonstrate its utility for high-resolution quantum microscopy. Strain imaging reveals the absence of detrimental strain profile. Spin coherence properties of the NVs are also characterized herein. Embodiments have been demonstrated for use in wide-field microscopy of electrical current. Diffraction-limited imaging has also been achieved. Aspects include deterministic transfer of DMCs with multiple materials of interest for next-generation electronics and spintronics, including a polymer-based technique for DMC placement. The embodiments discussed herein demonstrate DMC’s potential to expand the application of NV quantum sensing in materials, device, geological, biomedical, and chemical sciences.

[0047] The methods as described herein include use of DMCs containing an (111)- oriented NV ensemble for high-resolution quantum microscopy using a polymer-based technique for DMC placement. The DMCs may be placed on multiple novel spintronic and quantum materials and devices. Strain imaging shows an absence of a detrimental strain profile, establishing DMC’s utility for WFM. Spin coherence properties of the NVs are found to be consistent with expected NV depth. Aspects of the invention include demonstration of WFM of electrical current and diffraction-limited imaging. The methods as described herein may have applications for diamond-based dark matter detection.

[0048] An aspect of the invention thus relates to a method for performing wide-field microscopy (WFM) using nitrogen vacancy (NV) centers in diamond. Method steps include providing a wide-field microscopy (WFM) apparatus, such as is depicted in FIG. 1 . The exemplary WFM apparatus includes a holder (not shown) for receiving a sample 10 to be imaged. In the embodiments as described herein, a DMC 12 is disposed on top of and in contact with the sample. The DMC comprises an NV ensemble 14 (comprising a plurality of NV centers 13) therein. The WFM apparatus includes an objective (lens) for viewing optically with a camera 30, wherein the optical path also includes a lens 32 (e.g. a tube lens), and filter 34, a mirror 36, and dichroic beamsplitter 24, as shown. A laser 20 (e.g. 532 nm) sends a beam to the sample via a path passing through beam expansion lens 22, reflecting from the dichroic beamsplitter 24 through the objective to the DMC 12 on the sample 10. A microwave (MW) generation system, including generator 40, amplifier 42, and waveguide 44 sends MW energy to the sample. A specific embodiment of such a system is described in more detail below in the Examples.

[0049] The sample and DMC are shown in more detail in FIG. 2. Sample 10 to be studied with the WFM apparatus is disposed on holder 11 . DMC 12 having a (111)-oriented NV ensemble 13 is disposed on the sample in the path of the laser and optical beams of the WFM apparatus. In an exemplary method, the method of depositing the DMC on the sample includes the steps of providing a transparent substrate having a polymer microstructure on one surface thereof, contacting the DMC with the polymer microstructure on the transparent substrate, causing the DMC to temporarily adhere to the polymer microstructure, then approaching, with the transparent substrate and DMC adhered to the polymer microstructure, a position vertically above a placement location for of the DMC, and tilting the transparent substrate until the DMC detaches from the polymer microstructure and lands in a position in a vicinity of the placement location. If the landing position of the DMC is unacceptable, position of the DMC is fine tuned into an acceptable position relative to the placement location. Then an image of the sample is obtained using NV WFM through the DMC.

[0050] In accordance with one method, using a sharp tip, a DMC is broken off from the diamond sample onto a substrate (which may be a separate substrate from the target sample). A patterned polymer micro-structure on a transparent thin glass slide is then used to pick up the chip and subsequently bring it to the desired location on the target sample. To release the chip, the slide is tilted so the chip is gradually detached from the polymer micro-structure. Lastly, a tip can be used for fine-tuning of the chip placement. Because there is no need for the chip to traverse a long distance, little movement is required for the tip, and hence, there is minimal risk to the sample, the tip, and the DMC.

[0051] An exemplary polymer-assisted dry-transfer process is illustrated schematically in Figs. 3A-E. A DMC 300 is first broken off (e.g. with a tip 302) from a platform 304 holding an array of DMCs (discussed in more detail herein later) and lands on an intermediate substrate 306, as depicted in FIG. 3A. A transparent substrate 310 (e.g. a glass plate) with a polymer microstructure (e.g. a photoresist having an area that is smaller than the area of the chip) approaches the chip, as depicted in FIG. 3B. The polymer assembly picks up the DMC, as illustrated in FIG. 3C, and places it on (in contact with) or disposed above a sample of interest 317 (which is shown disposed on a sample holder 316 in FIG. 3D), such as by tilting the slide 310 to release the DMC from the polymer. A docking structure 315 having adhesive properties (e.g. comprising gold) that contacts the DMC may also further facilitate the release. Docking structure 315 is representative of a desired location to place the chip, such as a material with electrodes (e.g. wherein 315 represents the Ti / Au leads of an RuO2 altermagnet device as illustrated in FIGS. 3L and 3M), or a structure that defines a well for containing a liquid sample, or a structure that provides support for disposing the NVs a desired distance from a non-planar surface of the sample. As shown in FIG. 3E, the polymer assembly is pulled off, leaving the DMC on the sample. FIGS. 3F-3L are optical images of a polymer DMC deposition in action applied to depositing a 50 pm DMC 300 on a RuO2 altermagnet device 350 with Ti / Au leads. FIG. 3F shows a DMC 300 after being broken off, sitting on the intermediate substrate 306. In the image one also sees a glass slide 310 with a polymer micro-structure 312. FIG. 3G depicts the polymer assembly approaching and coming in contact with the DMC. The polymer assembly picks up the DMC, as depicted in FIG. 3H, which shows the optical image when the substrate is still in focus, meaning that the now out-of-focus DMC has been picked up, and FIG. 3I, which shows the DMC in focus and the substrate no longer in focus.

[0052] As shown in FIG. 3J, the polymer assembly brings the DMC on top of a RuO2 altermagnet Hall-bar device and deposits the DMC on the sample. The polymer assembly exits, while the DMC remains on the sample, as depicted in FIG. 3K As depicted in FIG. 3L, a tip can be used to further fine-tune the position. FIG. 3M shows the DMC from FIG. 3L after it has been picked up and transferred to another RuO2 Hall-bar device 352. The technique can also selectively transfer individual chips from a collection of closely- spaced chips.

[0053] One aspect of the techniques as described herein using DMC includes the methods for placing the chip at a desired location. When a chip detaches, it is not possible to control precisely where it lands; hence, most often the chip will land at some distance away from the desired location. The common prior art approach to position a chip is to subsequently push or drag it to the right place using a sharp tip. However, this has high probability of damaging the sample or rendering the tip / DMC unusable (picking up dirt, DMC stuck, etc). Hence, the fully tip-based method is not commensurate with high- throughput characterization. FIG. 4 shows a side / cross-sectional view of an exemplary process for DMC deposition on a substrate, such as sample 316. Detaching a DMC and subsequently positioning it at a location of interest, employs a sharp tip 302 (e.g. on a micro-positioner). The diamond-containing DMC array, with the NV surface 313 facing toward the surface of the sample 316 (or other intermediate substrate), is attached to a 3D translational I tilt stage 330, which enables the DMC array to get close to the substrate; ensuring the NV surface remains facing down (toward the sample) when the DMC is detached. When a DMC is broken off platform 304 holding an array of DMCs (see FIG. 3A), part of the bridge 305A remains on the platform, and part of the bridge 305B (FIG. 4B) remains on the chip. The off-center position of the bridge relative to a lateral centerline (CL) of the edge of the DMC introduces chirality, and once a chip has landed, confirmation that the NV surface is down can be ensured by looking at the location of the bridge and comparing it to the image of the chip prior to detachment, as illustrated in FIG. 4B.

[0054] As shown in Figs. 4C and 4D, the use of a patterned polymer microstructure 312 (i.e. disposed on only a discrete, intended portion of a transparent slide 310, but not completely covering it) enables picking up a specifically targeted chip (i.e. chip 300A) without affecting other chips in the neighborhood on substrate 306. This enables a high-throughput and highly-efficient process for deploying DMCs. A plurality of DMCs are detached from platform 304 onto intermediate substrate 306, as depicted in Fig. 4C. Then, each chip can be subsequently picked up from the intermediate substrate using the slide 310 and polymer 312, as shown in Fig. 4D, for later placement on the sample. The advantage of this process is two-fold. First, detachment can be done just once, instead of having to be done each time a chip is to be positioned, enabling greater efficiency. Second, this allows one to have chips detached and stored on a substrate, instead of remaining attached on the mainframe. The latter is risky for storage and transportation because chips can be easily detached with accident in handling; and if a chip is not detached in a controlled manner, it most likely cannot be retrieved. Hence, detaching many chips on a substrate for storage allows one to safely store the chips for transportation and handling; and can reduce costs associated with having to fabricate DMCs again due to an accident.

[0055] The transfer techniques as described herein differ from the method described by Ghiasi in a number of ways. The techniques as described herein deposit the chip directly on a substrate without Polydimethylsiloxane (PDMS). Risks of the diamond chip flipping upside down can be miminized as long as the gap between the chip and substrate is close enough (e.g. less than the lateral dimension of the DMC). Picking up a chip from a clean substrate is easier than that from sticky PDMS. The Ghiasi method requires preparation of a stamp comprising PDMS and polymethyl methacrylate (PMMA), which involves multiple polymer coating steps and a transfer to glass. The method as described herein includes direct deposit of photoresists on the glass without a transfer step and avoids additional fabrication procedures. The method as described herein directly uses the adhesion force between the photoresist and diamond chip to overcome the weight of the diamond to pick it up. The Ghiasi method requires heating the whole sample to 180C degrees to release the PMMA / diamond part from the stamp and then deposit it on the target sample, whereas such heating is not required in the method disclosed herein. Heating to 180C is not friendly to 2D samples, especially air sensitive samples, such as magnetic 2D flake. Moreover, the high temperature may also lead to irreversible change in the crystalline phases or magnetic properties of the sample. In addition, if the PMMA on top of the chip has to be removed, e-beam lithography is required to get rid of the PMMA. The Ghiasi method increases the difficulty of reusing the diamond chip, because eventually the chip is sealed by the melted PMMA on the sample position. In the method as described herein, the chip is reusable and can be reused indefinitely. The vdW forces between the diamond chip and the contact surface can seal the chip on the plane firmly without strong vibration. This re-usability enables a high-throughput process where one can first break off all the chips onto a substrate for storage, and when one needs to transfer a chip, one simply needs to perform the transfer from the storage substrate to the target sample.

[0056] In one aspect of the invention, DMCs were fabricated (Qnami) using protocol reported by Riedel et al. See, e.g., Riedel, D. et al., “Low-Loss Broadband Antenna for Efficient Photon Collection from a Coherent Spin in Diamond.” Phys. Rev. Appl. 2014, 2 (6), 064011 ; Riedel, D. et al., “Cavity-Enhanced Raman Scattering for In Situ Alignment and Characterization of Solid-State Microcavities.” Phys. Rev. Appl. 2020, 13 (1), 014036; Riedel, D., “Deterministic Enhancement of Coherent Photon Generation from a Nitrogen-Vacancy Center in Ultrapure Diamond.” Phys. Rev. X 2017, 7 (3), 031040, all incorporated herein by reference for all purposes. An array of DMCs were created having a range of lateral dimensions: 10*10, 20*20, and 50*50 pm2, with a thickness of ~1-2 pm. Each chip was attached to the mainframe via a small bridge. Nitrogen implantation at an energy of 10 keV with appropriate dosage created a quasi-2D NV ensemble with a density [NV]~1000 pm-2. DMCs were fabricated from single-crystal diamond substrate with (111) orientation, creating a class of NVs with a quantization axis set by the substitutional nitrogen and the vacancy along the vertical (z) direction.

[0057] DMCs can be integrated with a diverse range of materials of interest for next generation electronics and spintronics, including but not limited to: yttrium iron garnet grown via liquid phase epitaxy, a magnetic insulator with low magnon damping; magnetically-doped topological insulator hosting quantum anomalous Hall effects, grown via molecular beam epitaxy; altermagnet RuO2 Hall-bar device; a thin flake (<10 nm thick) of 50% Co-substituted Fe5GeTe2, which is a room-temperature van der Waals antiferromagnet; and a superconducting Josephson junction which provides a building block of a qubit.

[0058] A simplified Hamiltonian for NV spin is expressed in Equation 1 : where Dg=2.87 GHz is the ground-state zero-field splitting, Mzis the component of the effective electric field associated with strain (which we will call effective strain field) coupling to the (S2zterm, ye=28 GHz / T the gyromagnetic ratio, B the magnetic field, and S=(SX, SY, SZ) the S=1 spin operator. Here, the Z- axis corresponds to the quantization axis set by the nitrogen and vacancy. This Hamiltonian ignores higher-order contributions from strain which are negligible in the context of magnetometry. To leading order, the spin resonance corresponding to the ms= 0 <-> ±1 transitions are expressed by Equation 2: v±= D + yeBz+ 3ye2Bf / (2D)

[0059] [2] where the effective zero-field splitting (ZFS) DE Dg + Mzand B± is the off-axis field. In NV magnetometry, one typically applies an external bias field Boalong a particular NV axis so to be sensitive to the component of the target stray field parallel to this axis. Because off- axis field can lead to diminished spin-dependent PL contrast and worse spin coherence mediated by nearby13C, it is desirable to align Bowith an NV axis, in which case one is primarily sensitive to the component of the stray field along this axis. NV magnetometry has predominantly been performed with diamonds having (100) orientation, including previous works that have employed DMC, which has all the NV axes oriented at 54.7° with respect to the vertical. Aspects of our invention use DMC with an (111) orientation, where one NV axis is along the vertical direction. This is advantageous as it is the preferred direction for a large number of material science applications, and one can perform microscopy of vertical component of the stray field Bz, which is more optimal for interpretation and analysis. There is some concern that the fabrication process for DMCs may lead to modification of the local strain environment, and that inhomogeneous strain is a detriment to NV magnetometry. Accordingly, the spatial profile of the effective strain field Mz(x,y) of the (111)-oriented NVs (NVs with axis along the z- direction) was mapped, and strain microscopy was performed using known techniques. See, e.g., Marshall, M. C. et al., “High-Precision Mapping of Diamond Crystal Strain Using Quantum Interferometry,” Phys.Rev. Appl. 2022, 17 (2), 024041 ;Kehayias, P. et al., “Imaging Crystal Stress in Diamond Using Ensembles of Nitrogen-Vacancy Centers,” Phys. Rev. B 2019, 100 (17), 174103, both of which are incorporated herein by reference for all purposes. Figs. 5A-D, depicting the Mzprofile of two characteristic 10*10 pm2 chips, shows the absence of detrimental inhomogeneous strain. Distribution of axial strain field Mzas depicted in FIGS. 5A-2D show variation of local strain experienced by (111)-oriented NVs. FIG. 5A and 5B correspond to Mzfrom two different DMCs with the dimension (10 pm)2. The dashed edges show the boundary of the DMCs. FIGS. 5C and 5D are histograms of Mzgenerated from the DMC shown in FIGS. 5A and 5B respectively. Mean and standard deviation are -0.2 MHz and 0.1 MHz, respectively, for the DMC shown in FIG. 5A, and -0.55 MHz and 0.033 MHz for the DMC shown in FIG. 5B. Mean and one standard deviation are shown in the histograms as solid and dashed lines.

[0060] Two observations were immediately apparent. First, the variation of Mzis generally below 1 MHz within the bulk of the DMC. Furthermore, the dramatic strain profile associated with lattice dislocations, such as observed by Kehayias, supra, were absent. A more quantitative assessment of the strain characteristics is provided by the statistics of the histogram of Mz, as depicted in FIGS. 5C and 5D, which show a mono-modal distribution with a spread approximately given by standard deviation. The mean values may differ because of a difference in an overall, homogeneous strain environment or a difference in temperature. What is more important is that the spread of the Mzis small, with the standard deviations corresponding to a fractional strain of 3x106and 1 *10'6, respectively, comparable to the state-of-the-art value of 1 xiosfound in the quiet area of a bulk diamond single-crystal. This result demonstrates that fabricated DMC has favorable strain profile not too different from that of a bulk single-crystal diamond.

[0061] These results have implications for a proposed directional detection scheme of weakly interacting massive particle (WIMP), a candidate of dark matter (DM), via strain microscopy. To reconstruct the DM-induced strain tracks with nm-resolution while avoiding aberration, a typical mm-scale diamond needs to be thinned such that the DM impact site is close to the surface. A key feasibility question for detection of WIMPs is whether this fabrication process may introduce a strain feature that masks the strain signal induced by WIMPs. The standard deviation of strain of ~1-3x106is comparable to the expected WIMP signal of ~106. Hence, fabrication of small diamond structures a with a low strain variation that retains sensitivity to WIMP permits characterizing background strain features at nm scale.

[0062] The spin coherence properties of the (111)-oriented NVs in DMC were also characterized, as shown in Fig. 6A-6D2, which depict the optically-detected magnetic resonance (ODMR) spectrum of the NVs. Figs. 6A-6D2 illustrate coherent properties of (111)-oriented NVs in DMCs. The schematics of the measurement sequence are shown in the top of each panel. FIGS. 6A depicts optically detected magnetic resonance showing that hyperfine splitting is resolved and linewidth (half width half maximum) is 1.18(6) MHz. Figs. 6B1 and 6B2 show that Ramsey interferometry measures dephasing time T2* = 121 ns. Figs. 6C1 and 6C2 shows that Hahn spin-echo measures T2=2.3(3) ps. Fig. 6D1 and 6D2 depict a relaxometry measurement obtaining a longitudinal relaxation time Ti = 0.46(4) ms.

[0063] FIGS. 6A is a graph illustrating that hyperfine-splitting due to 14N nuclear spins is resolved and a linewidth (half width half maximum) of 1.22(7) MHz is obtained. This is comparable to a linewidth 1.5-2 MHz observed for NVs generated at similar density and implantation energy. The linewidth suggests that dephasing time T* should be a fraction of a ps. Ramsey interferometry (FIGS. 6B1 illustrating the Ramsey pulse sequence, and 6B2 showing results) showed T2* =121 ns. The dephasing time T * can be enhanced via, Hahn-echo sequence which shows T2=2.3(3) ps. Longitudinal relaxation time was found to be 7) = 0.46(4) ms. For shallow NV with d~10s nm, T2and Ti are closely tied to d. For a standard (100)-oriented diamond, Stopping Range of Ions in Matter (SRIM) estimates an average stopping range of the nitrogen ion to be ~15 nm with an implantation energy of 10 keV. However, for (111)-oriented diamond, SRIM finds that the stopping range can be reduced by as much as a factor of 2 55; hence, an average d on the order of 10 nm or below may be expected. To estimate d, we referred to published measurements forT) and T2of several NVs of various d. See, Sangtawesin, S. et al., “Origins of Diamond Surface Noise Probed by Correlating Single-Spin Measurements with Surface Spectroscopy,” Phys. Rev. X2019, 9 (3), 031052, incorporated herein by reference for all purposes. A value for d of ~8 nm best corresponds to the combination of Ti ~0.5 ms and T2~2 ps. This is consistent with measurements reported elsewhere, where for an NV ensemble finding T2~2.5 ps for d ~10 nm. See, Tetienne, J.-P.; et al., “Spin Properties of Dense Near-Surface Ensembles of Nitrogen-Vacancy Centers in Diamond.” Phys. Rev. B 2018, 97 (8), 085402, incorporated herein by reference for all purposes. Hence, we conclude that the spin coherence properties of the NV ensemble in a DMC is consistent with those at similar depth and density in standard bulk diamond single-crystal.

[0064] Figs. 7A-7D2 illustrates wide-field magnetic field imaging of stray-field Bzgenerated by current in a fabricated wire with a (111)-oriented NVs in (20 pm)2DMC samples. Fig. 7B illustrates a simulated stray-field Bz. Fig. 7C is a magnetic field map measured with current in the wire network. The overall pattern matches that of the simulation depicted in Fig. 7B, with some difference around the corners due to complexity in current flow not captured by the simulation. Fig. 7D1 depicts localized strain features that allow benchmarking of optical resolution, showing two localized strain features near each other. Mz is fitted to two Gaussians, with the contour of the two-dimensional fit shown. A linecut of the data (along dashed line 750 in FIG. 7D1) is shown in Fig.7D2 as points, with a fitted curve. The extracted spatial resolution is 450(30) nm.

[0065] Magnetic microscopy with DMC was performed using a 20x20 pm2DMC deposited on a fabricated meandering phantom wire, through which DC current was sent to generate a target magnetic field, as depicted in FIG. 7A. The availability of (111)-oriented diamond enabled direct measurement of Bz(the z-component of the stray-field). Fig. 7B shows a simulated Bzbased on a model of current flow. The stray-field Bzis shown in Fig. 7C, which clearly displays a distribution anticipated for z-component of magnetic field generated by a wire, other than for a small area around the corners where additional complexity in the real current flow is likely present and not captured by the simple model.

[0066] To characterize spatial resolution o, one approach is to fabricate a signal source with a spatial scale significantly smaller than o. Given the expected o ~100s nm, this approach would have required fabrication of a signal source significantly smaller than 100 nm, which is rather difficult. Instead, a small feature in the strain profile Mzwas identified and the size of the profile extracted. Fig. 7C shows one such profile used for characterizing resolution. The image shows two small point-like features in proximity to each other. Mz was fitted to the two Gaussian profiles and the size of the smaller feature extracted. Assuming the actual strain feature is much smaller than the spatial resolution, from the size of the feature, a spatial resolution of 450(30) nm was obtained, consistent with the expected resolution -440 nm due to the diffraction limit. This illustrates that magnetic microscopy at diffraction-limited resolution can be performed using DMC.

[0067] In one embodiment depicted in FIG. 9, a DMC 900 is disposed on a first surface on a first side (e.g. the top surface) of a base transparent substrate 902 and a microfluidics device 904 comprising a microfluidic channel 906 (with an inlet and outlet) is built on top of the DMC and first surface of the base transparent substrate. Exciting and detecting the NV ensemble of the DMC (e.g. with a WFM apparatus 910 as described herein) is then conducted from the opposite side (e.g. from the back side) of the base transparent substrate. As depicted, the NV ensemble faces up into the liquid sample flowing through the channel, as the NV ensemble is typically disposed as close to the sample to be analyzed as possible.

[0068] EXAMPLES

[0069] Robustness of DMC-sample interface

[0070] Once a DMC is properly placed on a sample, the sample can be transported between different locations and the DMC remains in place without being disturbed. A DMC also remain in its place after a wire bonding process. Generally, the DMC is deposited first, before wire bonding, as the bonding wires may otherwise be in the way for the diamond sample containing the DMC array to approach the sample of interest. Likewise, polymer- assisted transfer generally takes place prior to wire bonding. Experiments found that DMCs can also be held against gravity even without specialized surface preparation or adhesive material. For example, DMCs deposited on YIG or quartz substrates were shown to remain in place when the substrate was flipped over (e.g., in a measurement setup where the sample has to face down).

[0071] Experimental setup.

[0072] The setup for wide-field microscopy of strain (as shown in Fig. 1) and stray magnetic field as described herein is generally known, and not limited to any particular embodiment. See, e.g., Chen, H. et al., “Revealing Room Temperature Ferromagnetism in Exfoliated Fe5GeTe2 Flakes with Quantum Magnetic Imaging,” 2D Mater. 2022, 9 (2), 025017; and Chen, H.; et al., “Above-Room-Temperature Ferromagnetism in Thin van Der Waals Flakes of Cobalt-Substituted Fe5GeT 2." ACS Appl. Mater. Interfaces 2023, 15 (2), 3287-3296, both of which are incorporated herein by reference. A 532 nm laser 20 (Coherent Verdi 2G) provided excitation. In one suitable embodiment, the light was sent through a Kohler-illumination system consisting of a beam expansion lens 22 and a 0.9 NA air objective 16, which expanded the beam to illuminate an area of up to ~ 50x50 m2 on the sample. NV photoluminescence (PL) is collected by the same objective 16. The collected light is separated from the excitation via a 552 nm edge dichroic beamsplitter 24 (Semrock LM01-552-25). As the beam expansion lens 22 is located between the laser and the dichroic beamsplitter; the collected light does not pass through lens 22. After the dichroic beamsplitter 24, another 570 nm long-pass filter 34 (Semrock BLP01-647R-25) further removed light not in the PL wavelength range. The collected light was imaged via a tube lens 32 (focal length f = 200 mm) onto a CMOS camera 30 (Basler acA1920-155um). 2 * 2 binning was applied during data analysis, with each pixel corresponding to 140 nm on the sample. The microwave (MW) signal was sourced by a signal generator 40 (Stanford Research Systems SG384 or Windfreak USB3) and an amplifier 420(Minicircuits ZHL- 16W-43-S+).

[0073] In embodiments, the sample was fixed on a printed circuit board (PCB) with a co-planar waveguide (CPW). The sample substrate had a stripline wirebonded to the CPW of the PCB, to which the MW signal was delivered. The MW circuit ends with an MW terminator. For stray-field microscopy, the CPW also serves to provide the electrical connection between the phantom wire and the current source. The sample and the PCB are mounted on a combined manual translation stage and piezo positioner (Thorlabs NanoMax or Physiklnstrumente P-615.3CD NanoCube XYZ Piezo System). A permanent magnet mounted on a three-axes translational stage was used to provide an external bias magnetic field. Generally, the magnet was placed right beneath the sample to provide a vertical field aligned with (111)-oriented NVs.

[0074] The same system was modified as described below for pulsed measurements as described herein above (FIGS. 5A-5D). Excitation light was modulated with an acousto-optical modulator (AOM) powered by a radiofrequency (RF) driver (Gouch & Housego AOMO 3250-220 532nm and AODR 1250AFP-AD-6.6). Beam expansion light was removed so the excitation was focused onto a tight spot on the sample. The collected PL, instead of going through a tube lens and then imaged onto a camera, was directed into a single-mode fiber for confocal microscopy. The PL was finally detected by a single photon counting module (Excelitas 28252). Photon counting was performed with a Data Acquisition System (National Instrument USB-6361 , X Series DAQ Device with BNC Termination). A MW signal was supplied by Stanford Research Systems SG384 with built- in IQ control, and modulated with a switch. The NV interrogation pulse sequence was generated by a Swabian Instrument Pulse Streamer 8 / 2.

[0075] Strain and stray-field microscopy.

[0076] Wide-field microscopy was performed following known techniques, such as described by Chen et al., supra. An external bias magnetic field was aligned with (111)- oriented NVs. Optically-detected magnetic resonance (ODMR) measurements were performed by continuously illuminating the NVs with the excitation light while driving the NVs with an MW field. The MW frequency v was swept, and an ODMR image was captured at each MW frequency. To improve the signal-to-noise ratio (SNR), this sequence was repeated multiple times to create a set of images PLi,v(x,y). Post-measurement alignment of images was performed to counteract the effect of drift, before summing the images at a given to create a signal-averaged image PLV(x,y). Then, at a given pixel (x,y), an ODMR spectrum PL vs v was created and fit the spectrum to extract the resonance position. This procedure is performed to extract a spatial map of both the upper and lower NV resonances, v ±(x,y), corresponding to the ms= 0 ±1 transitions.

[0077] A simplified Hamiltonian for the NV electronic spin (assuming (111)- orientation) may be expressed as Equation 3:

[0078] H = (Dg+ Mz) Sz2+yeB ■ S [3] where Dg= 2.87 GHz is the ground-state zero-field splitting, Mzis the component of the effective electric field associated with strain (i.e. effective strain field) coupling to the Sz2term, ye=28 GHz / T is the NV gyromagnetic ratio, B is the net magnetic field applied to the NV, and S=(SX, Sy, Sz) is the S=1 spin operator. Here, the z-axis corresponds to the quantization axis set by the nitrogen and vacancy, which is also the vertical axis for (111)- oriented NVs. In writing down this Hamiltonian, we ignore higher-order contributions from strain, which are negligible in the context of magnetometry. To leading order, the spin resonance corresponding to the ms=0 <-> ±1 transitions are v± = D ± yeBz+ 3ye2B±2 / (2D), where the effective zero-field splitting (ZFS) is defined as D = Dg+Mzar\d Bxis the off-axis field.

[0079] For strain microscopy, the spatial map of effective zero-field splitting D = Dg+Mzwas obtained by extracting the common-mode shift, D(x,y)=[v+(x,y ) + v.(x,y)] / 2. Because the external magnetic bias field was aligned with the (111)-oriented NVs and there is no stray-field present, the magnetic field was completely aligned with (111)-oriented NVs and there was no contribution from an off-axis field B±. The effective strain field is then Mz(x,y) = D(x,y) - Dg, where Dg=2.87 GHz.

[0080] Due to a diamond’s high index of refraction, significant NV PL undergoes total internal refraction and exits the diamond at the edges. Hence, edges are generally brighter and often saturate the corresponding camera pixels. Furthermore, PL emitted near the edges contains information from other parts of the diamond. Hence in FIGS. 5A-5D, pixels within 1 pm of the edges as well as pixels with PL level exceeding a threshold value were filtered out.

[0081] For magnetic microscopy (Fig. 7c), differential shift, D v=[ (x,y)- u(x,y)] / 2, was converted to magnetic field via Bz= v / ys. While the stray-field from a current-carrying wire has an off-axis component in general, the leading-order contribution from the off-axis field to i4 is ~ B2and therefore contributes to the common-mode shift but not the differential shift.

[0082] Dark Matter Detection

[0083] One proposal for the directional detection of weakly interacting massive particles (WIMPs), a dark matter (DM) candidate, is via measurement of strain tracks in diamond left by WIMPs. In this multi-stage proposal, a large number of diamond crystals of ~mm3volume are stored in a facility (e.g., deep underground) to interact with WIMPs that pass through the diamond detector (Figs. 8A-C). Occasionally, a WIMP, or background particle such as a neutrino, initiates a nuclear recoil cascade via collision with a carbon nucleus and damages the diamond crystal lattice; the event is first registered and triangulated by photon, phonon, or charge-carrier collection (Fig. 8A). The diamond crystal in which the event is registered is isolated, and one then uses optical and / or x-ray techniques in to look for the associated strain feature, which needs to be eventually located with nm-resolution. The strategy would be to first perform-wide-field strain microscopy to locate the strain feature with pm or sub-pm precision (Fig. 8B), and at last perform microscopy with a super-resolution technique to achieve nm-resolution (Fig. 8c). To accomplish this goal, the diamond is thinned down to avoid aberration; hence, the DMC studied and discussed herein provides a representation of a suitable diamond sample for WIMP detection.

[0084] Fig 8A depicts exemplary schematics of directional WIMP detection. As depicted in Fig. 8A, an event is registered and the particular ~mm3volume of diamond crystal is identified for further measurement. As depicted in Fig. 8B, a registered diamond segment is taken for diffraction-limited microscopy, localizing the nuclear recoil track to a precision better than pm. As depicted in Fig. 8C, microscopy with ~nm resolution (e.g., via optical super resolution or x-ray techniques) is employed to measure the recoil track to nm precision. The incoming direction of the particle that created the nuclear recoil track can then be determined, potentially allowing discrimination of possible WIMPs from other background signals, such as from neutrinos.

[0085] Spatial resolution

[0086] Spatial resolution in optical microscopy is given by the associated point spread function (PSF). The PSF is given by the Airy pattern which has the form PSFAiiy(M)=(2Ji(M) / w)2, where u is some dimensionless spatial scale and is the Bessel function of the first kind of order one. The first zero occurs at u = 3.8317 = 4; the length scale corresponding to this u is the resolution according to the Rayleigh criterion. It is generally more convenient to use a Gaussian profile to approximate the PSF. The Airy pattern, to leading order in u, is PSFAiry = 1 - u2 / 4 + <9(u4). A Gaussian profile of the form exp(-u2 / 4) has the same expansion. Therefore, equation 4 is a suitable Gaussian PSF: and we identify 2a as the spatial resolution.

[0087] Figs. 7D1 , 7D2, show a fit of the two neighboring strain features to a Gaussian profile. The underlying strain features (before being broadened by optical diffraction) may not necessarily be symmetrical. To account for such asymmetry, each feature was fit to the form of Equation 5:

[0088] The larger strain feature has a significant aspect ratio, while the difference in ox and oy is within the error bar for the small feature. We take the smaller of ox and oy of the small feature, and from it extract a spatial resolution of 450(30) nm.

[0089] The diffraction-limited resolution from the Rayleigh criterion expected for an imaging system is A =0.61 A / NA, where A is the wavelength and NA is the numerical aperture of the objective. With a 0.9 NA objective and using A =650 nm as the typical wavelength for NV PL, gives A =440 nm, consistent with the experimentally extracted resolution.

[0090] Polymer-assisted dry-transfer

[0091] The polymer-assisted DMC pickup and drop-off process was accomplished on a homemade deposition apparatus as depicted in Figs. 3A-3M. With the diamond sample held on the translational stage on the left-hand-side, a DMC was first broken off from the diamond with a sharp tip mounted on the motorized translational stage on the right-hand-side. The distance between the diamond and the sample surface is kept as small as possible by adjusting the tilt stage, which eliminates the chance of the DMC flipping upside down during the landing process. Figs. 3A-3E demonstrate the schematic of picking up a DMC and transferring it onto a target sample. A micro-structure of polymer made of 0.7 m thick photoresist LOR5A / AZ-1512 was patterned on a transparent thin glass as shown in Fig. 3F. The polymer was located near the corner of the glass edges, which allows sufficient contact of the polymer to the DMC by slightly tilting the glass substrate. A 50 pm DMC was successfully picked up by the polymer as recorded in Fig. 53D-3I, where the images focuses on the DMC before and after it has been picked-up. Then the glass was moved to a location above the sample of interest. The sample shown in Fig. 3J was a patterned Hall bar structure of RuO2 with four leads made of 2 nm Ti / 100 nm Au. The DMC was vertically aligned to the sample location and gradually lowered down until it touches the Au leads as shown in Fig. 3J-3K. The tilt action and adhesion to the Au surface allowed the release of the DMC from the polymer to the targeted sample in Fig. 3K. Furthermore, a subsequent operation, shown in Fig. 3L, allowed slightly manipulating the DMC to a desired location or orientation using a sharp tip.

[0092] As discussed above, the technique as described herein differs from the reported dry-transfer technique of Ghiasi that uses a PMMA-PDMS stamp. First, the technique does not require thermal-assistance, which is desirable for a temperature or air sensitive material, e.g,. van der Waals magnetic materials. Second, the Ghiasi technique involves a PMMA layer that covers the whole diamond chip after the chip deposition, additionally requiring opening a window in PMMA layer by electron-beam lithography. In the method as disclosed herein, the DMC is directly dropped off on the sample, and no additional fabrication process is needed. Lastly, because the method as described hererin does not have a layer of PMMA that holds down the chip, the chips are recyclable.

[0093] Other sources report transfer techniques for diamond membranes having a thickness ~100 nm with lateral dimension ~100 pm. See, e.g., Guo, X. et al., “Tunable and Transferable Diamond Membranes for Integrated Quantum Technologies.” Nano Lett. 2021 , 21 (24), 10392-10399; Guo, X. et al., “Direct-Bonded Diamond Membranes for Heterogeneous Quantum and Electronic Technologies.” arXiv June 7, 2023 (collectively, Guo), incorporated herein by reference for all purposes. Differences from Guo include the transfer of significantly smaller structures, with lateral dimensions as small as 10 pm; and no requirement for specialized surface preparation, such as the use of a polymer adhesion layer (although the method as described herein can benefit from such a layer, it does not require it), plasma treatment, or annealing, which can place limitations on the types of samples that can interface with a DMC.

[0094] Thus, DMCs containing (111)-oriented NV ensemble can be used for high- resolution quantum microscopy. The absence of a detrimental strain profile and presence of spin coherence properties are consistent with that of the expected depth. Demonstrations of magnetic microscopy show that diffraction-limited resolution can be achieved when imaging through DMC. The method as described herein enables DMCs to interface with a diverse set of materials and has implications for particle physics applications. Although the invention is illustrated and described herein with reference to specific embodiments, the invention is not intended to be limited to the details shown. Rather, various modifications may be made in the details within the scope and range of equivalents of the claims and without departing from the invention.

Claims

What is Claimed:

1. A method for performing wide-field microscopy (WFM) using nitrogen vacancy (NV) centers in diamond, comprising the steps of: a) providing a wide-field microscopy (WFM) apparatus; b) providing a sample to be studied with the WFM apparatus; c) providing a diamond micro chip (DMC) having a (111)- oriented NV ensemble having an area; d) providing transparent substrate having a polymer microstructure on a portion of one surface thereof covering an area less than the area of the DMC; e) contacting the DMC with the polymer microstructure on the transparent substrate, causing the DMC to temporarily adhere to the polymer microstructure; f) approaching, with the transparent substrate and DMC adhered to the polymer microstructure, a position vertically above a placement location for of the DMC, and tilting the transparent substrate until the DMC detaches from the polymer microstructure and lands in a position in a vicinity of the placement location; g) if the landing position of the DMC is unacceptable, fine tuning position of the DMC into an acceptable position relative to the placement location. h) procuring an image of the sample using NV WFM through the DMC.

2. The method of claim 1 , wherein the step of providing the transparent substrate comprises providing the transparent substrate on a tiltable, 3D translational stage controlled by a micropositioner.

3. The method of claim 1 , comprising performing the fine tuning in step g) using a sharp tip of a micropositioner.

4. The method of claim 1 , comprising viewing the sample, the polymer microstructure, the DMC, or a combination thereof through an objective of the WFM apparatus while performing at least portions of one or more of steps d) - g).

5. The method of claim 4, wherein the step of providing the DMC comprises providing an array of DMCs and detaching a selected one of the DMCs from the array.

6. The method of claim 5, wherein the array of DMCs comprises a plurality of DMCs each attached to an array substrate by a bridge connecting an edge ofeach DMC to an edge of the array substrate, and detaching a selected one of the DMCs from the array comprises using a sharp tip to break off the chip from the array.

7. The method of claim 6, wherein the bridge connecting the edge of each DMC to the array is off-center relative to a lateral centerline of the DMC intersecting the connecting edge, and breaking off the DMC from the array leaves a stub on the edge of the DMC, further comprising in step f), viewing an orientation of a stub on the edge of the DMC through the objective of the WFM apparatus to confirm that a desired face of the DMC is facing the objective.

8. The method of claim 6, comprising detaching the selected one of the DMCs so that it falls onto an intermediate substrate, and then performing step (e) to pick up the DMC from the intermediate substrate using the transparent substrate with the polymer microstructure.

9. The method of claim 1 , wherein the DMC has a thickness ~1-2 pm.

10. The method of claim 8, wherein the DMC has a square geometry with a lateral dimension in the range of 10 - 50 pm.11 . The method of claim 10, wherein the DMC has a variation of Mz below 1 MHz with standard deviations corresponding to a fractional strain in a range of 1x10-6- 3x10-6.

12. The method of claim 1 , comprising using a first DMC to perform steps f)-h) on a first sample, then removing the DMC from the first sample, and performing steps f)-h) on a second sample.

13. The method of claim 1 , wherein the sample comprises a microfluidic channel, wherein steps d)-g) comprise depositing the DMC on a first surface of a base transparent substrate and building a microfluidic channel on top of the front side of the base transparent substrate.

14. The method of claim 13, wherein the base transparent substrate has first and second opposite sides and first surface of the base transparent substrate is disposed on the first side, further comprising exciting and detecting the NV ensemble of the DMC during step h) from the second side of the base transparent substrate.

15. The method of claim 1 , wherein step h) comprises performing strain microscopy.

16. The method of claim 1 , wherein step h) comprises performing microscopy of electrical current, magnetization, or spin relating to the sample.

17. The method of claim 1 , wherein the transparent substrate has no polymer adhesion layer and has not undergone plasma treatment or annealing in theportion of the slide where the polymer is disposed prior to the polymer being disposed on the slide.

18. The method of claim 1 , wherein the sample to be studied is the DMC, and the step of procuring the image of the sample includes locating a strain feature in the DMC with pm or sub-pm precision.

19. The method of claim 18, further comprising determining an incoming direction of a particle involved in a particle collision with the DMC based upon detection of a nuclear recoil track created in the DMC by the particle.

Images