Dual-probe tunneling electron beam transmission detection device and alignment and transmission detection method

Abstract

The application discloses a double-probe tunneling electron beam transmission detection device and an alignment and transmission detection method in the field of nano detection technology, which comprises a bottom plate, a first probe assembly and a second probe assembly are symmetrically arranged on the bottom plate, and a sample conveying mechanism is arranged between the two probe assemblies; the first probe assembly comprises a first nano probe with a first tip; the second probe assembly comprises a second nano probe with a second tip, the second tip is arranged opposite to the first tip, and a tunneling gap is formed between the two tips; a bias power supply is connected between the first nano probe and the second nano probe, and is used for applying a bias between the two probes to generate a tunneling electron beam in the tunneling gap; the device can be used for transmission imaging, cross-section profile measurement and three-dimensional topography reconstruction of nano-scale material structures, and can also be used for measuring tunneling electron characteristics in basic physical research, alignment locking is realized by searching for a maximum value of a tunneling current through XY plane scanning, and the tips of the two probes are accurately aligned in the nano scale.

Description

Technical Field

[0001] This invention relates to a dual-probe tunneling electron beam transmission detection device and its alignment and transmission detection method in the field of nanotechnology. Background Technology

[0002] Scanning tunneling microscopy (STM) is a landmark technology in the field of nanoprobes. Its basic principle is to bring a conductive probe close to the surface of a conductive sample and apply a bias voltage between the probe and the sample. When the distance between the probe and the sample is less than about 1 nm, a tunneling current is generated. By measuring the tunneling current, information about the surface morphology and electronic density of states of the sample can be obtained. STM and its derivative technologies (such as electrochemical STM and scanning tunneling spectroscopy) have achieved great success in the field of surface science.

[0003] However, existing STM technology has the following inherent limitations: (1) Reflective detection mode. STM adopts a probe-sample reflective configuration, where tunneling current is generated between the probe and the sample surface. It can only acquire information from the outermost surface of the sample and cannot directly detect the internal structure of the material. This is similar to being able to see the reflected light of an object but not to perform transmission observation.

[0004] (2) Tunneling current is only a signal. In all existing technologies, tunneling current is only used as a measurement signal for distance or conductance, that is, the probe-sample spacing or sample surface electronic state is inferred from the current magnitude, and the tunneling electrons themselves are not given any functional role.

[0005] (3) The electron beam is uncontrollable. The path of the tunneling electron in STM is determined by the geometric relationship between the probe tip and the sample surface. It is impossible to manipulate the electron beam in space (such as focusing, deflecting, scanning), so it does not have the ability to actively scan and detect in three-dimensional space.

[0006] (4) The sample must be conductive. STM relies on the formation of a tunneling junction between the probe and the sample. The sample must be conductive or have a conductive layer on its surface. Non-conductive samples (such as biological tissues and insulators) cannot be measured directly; the conductive layer will change the micro-nano scale sample structure.

[0007] (5) Probe physical contact with the sample. Although atomic force microscopy (AFM) can measure non-conductive samples, its tapping mode causes irreversible damage to soft samples such as biological tissues, and the measurement accuracy is limited by the radius of curvature of the probe tip and the contact mechanics.

[0008] Chinese patent CN120446536A discloses a tip-to-tip scanning probe measurement device, in which two tips are positioned opposite each other to form a tunneling junction. However, the purpose of this patent is to solve the signal aliasing problem caused by the mismatch between the tip and sample scale in traditional STM. Its tunneling current is still only used as a measurement signal; it does not use the tunneling electron beam as a detection tool, nor does it propose a technical solution for allowing material to pass between the two probes for transmission detection. In the technical solution of this patent, the sample is located outside the two probes, and the tunneling electron beam needs to remain stable and undisturbed to achieve high-precision surface imaging—if the sample is placed between the two probes, it would precisely disrupt the stable imaging conditions it seeks.

[0009] Therefore, there is an urgent need in the field for a technical solution that can transform the tunneling electron beam from a passive signal into an active detection tool, so as to achieve transmission detection of the internal structure of nanoscale materials without being limited by the conductivity of the sample or having physical contact with the sample.

[0010] Furthermore, in the field of fundamental physics, the tunneling time problem has remained unresolved since the Hartman effect was proposed. Theoretical predictions state that the effective time for tunneling electrons to pass through a potential barrier tends to saturate as the barrier thickness increases, implying that the effective speed may exceed the speed of light. However, this prediction has lacked direct experimental verification for ninety years. In current technologies, tunneling electrons are only used as signals, and the tunneling electron beam cannot be independently manipulated and measured, thus making it impossible to directly measure the velocity of tunneling electrons. Summary of the Invention

[0011] The purpose of this invention is to provide a dual-probe tunneling electron beam transmission detection device and an alignment and transmission detection method, which can be used for transmission imaging of nanoscale material structures, cross-sectional profile measurement and three-dimensional morphology reconstruction. Furthermore, the device provided by this invention can also be used for measuring the tunneling electron properties in fundamental physics research.

[0012] To achieve the above objectives, the present invention provides a dual-probe tunneling electron beam transmission detection device, including a base plate, on which a first probe assembly and a second probe assembly are symmetrically arranged, and a sample delivery mechanism is arranged between the two probe assemblies. The first probe assembly includes a first nanoprobe having a first tip; The second probe assembly includes a second nanoprobe with a second tip, the second tip being disposed opposite to the first tip, and a tunneling gap being formed between them; A bias power supply is connected between the first nanoprobe and the second nanoprobe to apply a bias voltage between the two probes to generate a tunneling electron beam in the tunneling gap. A current detector is also connected in series between the first nanoprobe and the second nanoprobe to detect the tunneling current flowing between the first nanoprobe and the second nanoprobe. The current detector is connected to the signal processor and is used to obtain the internal structure information of the sample under test based on the changes in the on / off state of the tunneling current. The changes in the on / off state of the tunneling current include the interruption of the current when the tunneling electron beam is blocked by the sample under test and the normal flow of the current when it is not blocked.

[0013] As a further improvement of the present invention, the first probe assembly further includes a first probe three-dimensional coarse adjustment stage, a first probe three-dimensional fine adjustment stage is provided on the first probe three-dimensional coarse adjustment stage, a first probe support base is provided on the first probe support base, a first probe support is provided on the first probe support base, a first nanoprobe is installed at the end of the first probe support, a first locking device is provided on the first probe support, and the first locking device is provided on the first locking device base. The second probe assembly also includes a second probe three-dimensional coarse adjustment stage, a second probe three-dimensional fine adjustment stage, a second probe support base, a second probe support on the second probe support base, a second nanoprobe installed at the end of the second probe support, and a second locking device on the second probe support, which is located on the second locking device base.

[0014] As a further improvement of the present invention, the sample conveying mechanism includes a first sample three-dimensional coarse adjustment worktable and a second sample three-dimensional coarse adjustment worktable, a first sample three-dimensional fine adjustment worktable is provided on the first sample three-dimensional coarse adjustment worktable, and a first rotating device is provided on the first sample three-dimensional fine adjustment worktable. The second sample three-dimensional coarse adjustment worktable is equipped with a second sample three-dimensional fine adjustment worktable, and a second rotating device is provided on the second sample three-dimensional fine adjustment worktable. The first rotating device and the second rotating device are symmetrically arranged, and the first rotating device and the second rotating device cooperate with each other to clamp the same sample to be tested.

[0015] As a further improvement of the present invention, the first probe assembly, the second probe assembly, the sample delivery mechanism, and the base plate are all located in an environmental isolation chamber, and the medium in the environmental isolation chamber is any one of vacuum, non-conductive gas, or non-conductive liquid.

[0016] As a further improvement of the present invention, when the medium is a non-conductive gas, its conductivity is not greater than 10. -10 S / m; when the medium is a non-conductive liquid, its conductivity is not greater than 10. -6 S / m; The medium is vacuum, and the vacuum level inside the environmental isolation chamber is no greater than 10. -4 Pa.

[0017] As a further improvement of the present invention, the environmental isolation cavity is installed on the vibration isolation platform, and the natural frequency of the vibration isolation platform is not greater than 5Hz.

[0018] As a further improvement of the present invention, the radius of curvature of the first tip and the second tip is no greater than 50 nm, and the distance between the first tip and the second tip is 1 nm to 20 nm.

[0019] As a further improvement of the present invention, both the first locking device and the second locking device are magnetic powder brakes.

[0020] To achieve the above objectives, the present invention also provides a dual-probe tunneling electron beam alignment and transmission detection method, comprising the following contents: S1. The first tip of the first nanoprobe and the second tip of the second nanoprobe are positioned opposite each other so that the two tips are roughly facing each other. S2. Drive the second nanoprobe to scan point by point in the XY plane, where the Z-axis direction is the direction of the line connecting the two tips. Detect the tunneling current between the two probes at each scanning point and record the XY position corresponding to the maximum value of the tunneling current. S3. Lock the second nanoprobe at the XY position corresponding to the maximum value of the tunneling current to complete the alignment of the two tips in the XY plane; S4. Adjust the distance between the two tips to the target working distance via Z-axis feed, and lock the Z-axis position; S5. Apply a bias voltage between the two probes to generate a stable tunneling electron beam between the two tips and detect the initial tunneling current. S6. The sample to be tested is transported to the tunneling gap between the first tip and the second tip, so that the sample to be tested is placed on the transmission path of the tunneling electron beam. The sample to be tested does not participate in the conductive circuit, but only acts as a shield for the tunneling electron beam. When the tunneling electron beam is shielded by the sample to be tested, the tunneling current is interrupted. When the tunneling electron beam is not shielded, the tunneling current flows normally. S7. Detect the change in the on / off state of the tunneling current. When the current drops sharply from the normal value to zero, record the position as the shielding boundary of the sample. When the current returns to normal from zero, record the position as the other side boundary of the sample. The distance between the two jump points is the radial dimension of the sample under test in that direction. S8. Drive the sample to be tested to rotate around its own axis by a fixed angle through the first rotating device and the second rotating device. Perform Z-direction scanning detection again at this rotation angle, that is, repeat the operation of step S7 to obtain the radial dimension of the sample to be tested at this rotation angle. S9. Repeat step S8 until the sample under test has rotated a total of 360 degrees. Summarize the radial dimension data corresponding to all rotation angles, mark each measuring point in the coordinate system, and connect all measuring points with a smooth curve to reconstruct the cross-sectional profile of the sample under test.

[0021] As a further improvement of the present invention, after the measurement of a single cross-sectional profile is completed, the sample is moved by a set step distance along the length direction of the sample to be measured, and steps S8 and S9 are repeated to obtain the cross-sectional profile of the next position; the cross-sectional profiles corresponding to all step distances within the specified length are collected in sequence, and all cross-sectional profiles are spliced ​​together in three-dimensional space to reconstruct the three-dimensional morphology of the sample to be measured.

[0022] Compared with the prior art, the beneficial effects of the present invention are as follows: (1) For the first time, the tunneling electron beam is transformed from a passive signal into an active detection tool. In the prior art, the tunneling current is only used as a measurement signal for distance or conductance. This invention compares the tunneling electron beam to X-rays, making it a transmission detection tool that irradiates through matter. When the electron beam is blocked by matter, the current drops to zero. When the electron beam path is unobstructed, the current flows normally. This "on-off" switching characteristic is used to realize the detection of material structure, realizing a paradigm shift from "reflection detection" to "transmission detection".

[0023] (2) Extremely high on / off detection accuracy and strong noise resistance. This invention does not estimate structural information based on the current gradient, but rather detects sharp current jump points—the current suddenly drops from its normal value to zero or recovers from zero to normal. This digital 0 / 1 jump detection has higher accuracy and noise resistance than analog gradient estimation, and does not depend on the stability of the absolute value of the current, but only on the change in the on / off state. Existing tip-to-tip imaging devices are limited by the accuracy of current gradient estimation (typical spatial resolution on the order of 0.1 nm). This invention uses sharp jumps in the on / off state for detection. Theoretically, its resolution depends only on the positioning accuracy of the displacement stage (up to 0.01 nm), and does not depend on the stability of the absolute value of the current. Therefore, it has higher measurement accuracy and repeatability.

[0024] (3) Achieving transmission detection of the internal structure of materials at the nanoscale. Existing technologies such as STM can only obtain information about the sample surface. This invention allows the sample to pass between two probes. When the tunneling electron beam is blocked by the sample, the current is interrupted, and when it is not blocked, the current is restored. Information about the internal structure of the material can be directly obtained, with a spatial resolution of up to 0.01 nm.

[0025] (4) No sample conductivity is required; insulating samples can be measured directly. In this invention, the tunneling electron beam is generated between the two probe tips. The sample to be measured only acts as a shield in the electron beam path and does not participate in the conductive circuit. Therefore, it can be measured directly regardless of whether the sample is conductive or not, without the need to coat the insulating sample with a conductive layer, thus avoiding changes to the micro / nano structure and measurement errors caused by the coating. This effect is something that those skilled in the art could not reasonably foresee after reading the prior art—the technical routes of the prior art (including STM and tip-to-tip imaging devices) all require the sample to be conductive or to be coated with a conductive layer. This invention completely breaks through this limitation.

[0026] (5) No physical contact with the sample. This invention utilizes the shielding effect of the electron beam for detection. The electron beam is an electron probability flow and does not apply physical contact force to the sample. Therefore, it does not cause damage to fragile samples such as biological tissues and flexible materials, thus overcoming the problem of irreversible damage to biological tissues caused by the tapping mode of AFM.

[0027] (6) Obtain the complete cross-sectional profile by rotation measurement. The sample is rotated 360 degrees around its own axis by a rotating device. The radial dimension is measured sequentially at multiple rotation angles, which can reconstruct the complete cross-sectional profile of the sample. This method is applicable not only to circular cross-sections but also to any irregular cross-sectional shape.

[0028] (7) Reconstruct the three-dimensional morphology by scanning each section. By measuring each section along the length of the sample and stitching together the contours of all sections, the complete three-dimensional surface morphology and all geometric dimensions of the sample can be reconstructed.

[0029] (8) Double-sided clamping improves stability. Two rotating devices work together to clamp the same fibrous sample from both ends, preventing the long fiber from swaying or falling off during rotation and movement, thus improving measurement accuracy and repeatability.

[0030] (9) Gradual locking of magnetic powder brake. Gradual locking is achieved by gradually applying current, and with the dynamic feedback control of the fine-tuning table, impact and displacement during the locking process are avoided, ensuring the final locking accuracy of the probe position.

[0031] (10) Alignment locking is achieved by scanning the XY plane to find the maximum value of the tunneling current, ensuring that the tips of the two probes are precisely aligned at the nanoscale. Alignment is a prerequisite for the stable operation of the tunneling electron beam—the tunneling electron beam has the maximum current density and the highest spatial resolution only when the two tips are aligned at the closest distance. This method uses the exponential sensitivity of the tunneling current itself as the alignment criterion, and achieves self-alignment without the need for an external optical alignment system. Attached Figure Description

[0032] Appendix Figure 1 This is a schematic diagram of the main structure of the dual-probe tunneling electron beam transmission detection device of the present invention.

[0033] Appendix Figure 2 This is a schematic diagram of the tunneling electron beam transmission detection principle of the present invention, wherein (a) shows the electron beam is directly connected and the current is normal when there is no sample, and (b) shows the electron beam is blocked and the current is interrupted when there is a sample.

[0034] Appendix Figure 3 This is a schematic diagram of the probe assembly structure of the present invention, wherein (a) is the first probe assembly and (b) is the second probe assembly.

[0035] Appendix Figure 4 This is a schematic diagram of the prototype device of the present invention.

[0036] Appendix Figure 5 This is a schematic diagram of the rotating cross-section measurement method of the present invention.

[0037] Appendix Figure 6 The diagram shows three working media of the environmental isolation cavity of the present invention, where (a) is a vacuum environment, (b) is a non-conductive gas environment, and (c) is a non-conductive liquid environment.

[0038] Appendix Figure 7 This is a schematic diagram showing the layout of the main body of the device of the present invention within the environmental isolation cavity and vibration isolation platform.

[0039] Among them, 1 is the base plate, 101 is the unshielded tunneling electron beam, 102 is the tunneling current, 103 is the shielded tunneling electron beam, 104 is the current detector, 105 is the bias power supply, and 106 is the signal processor. 2 First probe assembly, 201 First probe three-dimensional coarse adjustment stage, 202 First probe three-dimensional fine adjustment stage, 203 First probe support base, 204 First probe support, 205 First locking device, 206 First nano probe, 207 First locking device base. 3 Sample conveying mechanism, 301 First sample three-dimensional coarse adjustment worktable, 302 First sample three-dimensional fine adjustment worktable, 303 First rotating device, 304 Sample to be tested, 305 Second rotating device, 306 Second sample three-dimensional fine adjustment worktable, 307 Second sample three-dimensional coarse adjustment worktable. 4 Second probe assembly 401 Second probe three-dimensional coarse adjustment stage, 402 Second probe three-dimensional fine adjustment stage, 403 Second probe support base, 404 Second probe support, 405 Second locking device, 406 Second nano probe, 407 Second locking device base. 5. Environmental isolation cavity; 6. Vibration isolation platform. Detailed Implementation

[0040] The present invention will be further described below with reference to the accompanying drawings: like Figure 1-7 The dual-probe tunneling electron beam transmission detection device shown includes a base plate 1, on which a first probe assembly 2 and a second probe assembly 4 are symmetrically arranged, and a sample delivery mechanism 3 is arranged between the two probe assemblies. The first probe assembly 2 includes a first nanoprobe 206 having a first tip; The second probe assembly 4 includes a second nanoprobe 406 having a second tip, the second tip being disposed opposite to the first tip, and a tunneling gap being formed between them; A bias power supply 105 is connected between the first nanoprobe 206 and the second nanoprobe 406 to apply a bias voltage between the two probes to generate a tunneling electron beam in the tunneling gap. A current detector 104 is connected in series between the first nanoprobe 206 and the second nanoprobe 406 to detect the tunneling current 102 flowing between the first nanoprobe 206 and the second nanoprobe 406. The current detector 104 is connected to the signal processor 106 and is used to obtain the internal structure information of the sample 304 under test based on the on / off state changes of the tunneling current 102. The on / off state changes of the tunneling current 102 include the interruption of the current when the tunneling electron beam is blocked by the sample 304 under test and the normal flow of the current when it is not blocked.

[0041] The first probe assembly 2 also includes a first probe three-dimensional coarse adjustment stage 201, a first probe three-dimensional fine adjustment stage 202 is provided on the first probe three-dimensional coarse adjustment stage 201, a first probe support base 203 is provided on the first probe support base 203, a first probe support 204 is provided on the first probe support base 203, a first nanoprobe 206 is installed at the end of the first probe support 204, a first locking device 205 is provided on the first probe support 204, and the first locking device 205 is provided on the first locking device base 207. The second probe assembly 4 also includes a second probe three-dimensional coarse adjustment stage 401, a second probe three-dimensional fine adjustment stage 402 is provided on the second probe three-dimensional coarse adjustment stage 401, a second probe support base 403 is provided on the second probe support base 402, a second probe support 404 is provided on the second probe support base 403, a second nanoprobe 406 is installed at the end of the second probe support 404, a second locking device 405 is provided on the second probe support 404, and the second locking device 405 is provided on the second locking device base 407.

[0042] The sample conveying mechanism 3 includes a first sample three-dimensional coarse adjustment worktable 301 and a second sample three-dimensional coarse adjustment worktable 307. A first sample three-dimensional fine adjustment worktable 302 is provided on the first sample three-dimensional coarse adjustment worktable 301, and a first rotating device 303 is provided on the first sample three-dimensional fine adjustment worktable 302. The second sample three-dimensional coarse adjustment worktable 307 is provided with a second sample three-dimensional fine adjustment worktable 306, and the second sample three-dimensional fine adjustment worktable 306 is provided with a second rotating device 305. The first rotating device 303 and the second rotating device 305 are symmetrically arranged, and the first rotating device 303 and the second rotating device 305 cooperate with each other to clamp the same sample 304 to be tested.

[0043] The first probe assembly 2, the second probe assembly 4, the sample delivery mechanism 3, and the base plate 1 are all located inside the environmental isolation chamber 5. The medium inside the environmental isolation chamber 5 is any one of vacuum, non-conductive gas, or non-conductive liquid.

[0044] When the medium is a non-conductive gas, its conductivity is no greater than 10. -10 S / m; when the medium is a non-conductive liquid, its conductivity is not greater than 10. -6 S / m; The medium is vacuum, and the vacuum level inside the environmental isolation chamber 5 is no greater than 10. -4 Pa.

[0045] The environmental isolation cavity 5 is installed on the vibration isolation platform 6, and the natural frequency of the vibration isolation platform 6 is no greater than 5Hz.

[0046] The radius of curvature of the first and second tips is no greater than 50 nm, and the distance between the first and second tips is 1 nm to 20 nm.

[0047] Both the first locking device 205 and the second locking device 405 are magnetic powder brakes.

[0048] like Figure 1-7 The dual-probe tunneling electron beam alignment and transmission detection method shown includes the following: S1. The first tip of the first nanoprobe 206 and the second tip of the second nanoprobe 406 are positioned opposite each other so that the two tips are roughly facing each other. S2. Drive the second nanoprobe 406 to scan point by point in the XY plane, where the Z-axis direction is the direction of the line connecting the two tips. Detect the tunneling current 102 between the two probes at each scanning point and record the XY position corresponding to the maximum value of the tunneling current 102. S3. Lock the second nanoprobe 406 at the XY position corresponding to the maximum value of the tunneling current 102 to complete the alignment of the two tips in the XY plane. S4. Adjust the distance between the two tips to the target working distance via Z-axis feed, and lock the Z-axis position; S5. Apply a bias voltage between the two probes to generate a stable tunneling electron beam between the two tips, and detect the initial tunneling current 102. S6. The sample to be tested 304 is transported to the tunneling gap between the first tip and the second tip, so that the sample to be tested 304 is placed on the transmission path of the tunneling electron beam. The sample to be tested 304 does not participate in the conductive circuit, but only acts as a shield for the tunneling electron beam. When the tunneling electron beam is blocked by the sample to be tested 304, the tunneling current 102 is interrupted. When the tunneling electron beam is not blocked, the tunneling current 102 flows normally. S7. Detect the on / off state change of the tunneling current 102. When the current drops sharply from the normal value to zero, record the position as the shielding boundary of the sample. When the current returns to normal from zero, record the position as the other side boundary of the sample. The distance between the two jump points is the radial dimension of the sample 304 under test in this direction. S8. Drive the sample to be tested to rotate around its own axis by a fixed angle through the first rotating device and the second rotating device. Perform Z-direction scanning detection again at this rotation angle, that is, repeat the operation of step S7 to obtain the radial dimension of the sample to be tested at this rotation angle. S9. Repeat step S8 until the sample 304 under test has rotated a total of 360 degrees. Summarize the radial dimension data corresponding to all rotation angles, mark each measuring point in the coordinate system, and connect all measuring points with a smooth curve to reconstruct the cross-sectional profile of the sample 304 under test.

[0049] After the single cross-sectional profile measurement is completed, move along the length direction of the sample 304 to be tested by a set step distance, and repeat steps S8 and S9 to obtain the cross-sectional profile of the next position; sequentially collect the cross-sectional profiles corresponding to all step distances within the specified length, and continuously stitch all cross-sectional profiles in three-dimensional space to reconstruct the three-dimensional morphology of the sample 304 to be tested.

[0050] In this invention, such as Figure 1 As shown, the dual-probe tunneling electron beam transmission detection device includes a base plate 1, on which a first probe assembly 2 and a second probe assembly 4 are symmetrically arranged, and a sample delivery mechanism 3 is arranged between the two probe assemblies.

[0051] As attached Figure 3 As shown, the first probe assembly 2 includes a first probe three-dimensional coarse adjustment stage 201, a first probe three-dimensional fine adjustment stage 202, a first probe support base 203, a first probe support 204, a first locking device 205, a first nanoprobe 206, and a first locking device base 207. The first nanoprobe 206 has a first tip, which is prepared by electrochemical etching of a tungsten wire, with a radius of curvature of approximately 20 nm. The second probe assembly 4 has a symmetrical and identical structure, including a second probe three-dimensional coarse adjustment stage 401, a second probe three-dimensional fine adjustment stage 402, a second probe support base 403, a second probe support 404, a second locking device 405, a second nanoprobe 406, and a second locking device base 407.

[0052] The first nanoprobe 206 and the second nanoprobe 406 are arranged facing each other with collinear axes, forming a tunneling gap between their tips. A bias power supply 105 is connected between the first nanoprobe 206 and the second nanoprobe 406, applying a bias voltage of approximately 100mV to generate a tunneling electron beam in the tunneling gap. Electrons tunnel from the first tip to the second tip, forming a tunneling current 102 of approximately 1nA.

[0053] A current detector 104 is connected in series between the first nanoprobe 206 and the second nanoprobe 406 for real-time detection of the tunneling current 102.

[0054] As attached Figure 4As shown, the sample transport mechanism 3 includes a first three-dimensional coarse adjustment stage 301, a first three-dimensional fine adjustment stage 302, a first rotating device 303, a sample to be tested 304, a second rotating device 305, a second three-dimensional fine adjustment stage 306, and a second three-dimensional coarse adjustment stage 307. The two sets of fine adjustment stages and rotating devices work together to clamp both ends of the same fibrous sample to be tested 304, forming a double-sided clamping structure. The sample to be tested 304 has a diameter of less than 2 nm and is placed in the tunneling gap between the tips of the two probes.

[0055] It should be noted that the sample 304 under test does not participate in the conductive circuit, but only serves as a shield for the tunneling electron beam—this is the fundamental difference between the present invention and the prior art.

[0056] As attached Figure 2 As shown in (a), when there is no sample, the unobstructed tunneling electron beam 101 flows directly from the first tip to the second tip, and the current detector 104 measures the initial tunneling current I0, indicating normal current flow. (See attached diagram.) Figure 2 As shown in (b), when the sample 304 is placed in the electron beam transmission path, the tunneling electron beam is blocked by the sample, i.e., the blocked tunneling electron beam 103. Electrons cannot reach the second tip from the first tip, and the tunneling current 102 drops sharply to zero. The change in current ΔI = I0 - 0 = I0, that is, the change in current is equal to the full value of the initial current. This "on-off" switching characteristic provides a very clear criterion for the detection of material structure—not by estimating on the current gradient, but by detecting sharp current jump points.

[0057] The signal processor 106 is connected to the current detector 104 and receives the on / off state change signal of the tunneling current 102. It calculates the structural size information of the sample based on the scanning position corresponding to the current jump. The signal processor 106 detects the change in the on / off state of the tunneling electron beam caused by whether or not it is blocked by the sample under test, rather than measuring the distance or conductance between the two tips—this is a concrete manifestation of the present invention transforming the tunneling electron beam from a "passive signal" into an "active detection tool".

[0058] The probe positioning and locking process is as follows: During operation, the positions of the first nanoprobe 206 and the second nanoprobe 406 are first coarsely adjusted in the XYZ directions using the first probe three-dimensional coarse adjustment stage 201 and the first probe three-dimensional fine adjustment stage 202, respectively. Then, the three-axis positions of the first nanoprobe 206 and the second nanoprobe 406 are finely adjusted using the first probe three-dimensional fine adjustment stage 202 and the second probe three-dimensional fine adjustment stage 402, respectively, while simultaneously performing XY-axis scanning. The scanning adopts a method of fixing one probe and moving the other probe for scanning. After the scanning is completed, the spatial position corresponding to the maximum value of the tunneling current 102 is selected—since the tunneling current 102 is exponentially sensitive to the spacing, the maximum current value corresponds to the closest distance between the two tips in the XY direction.

[0059] Once the position is determined, the first probe 3D coarse adjustment stage 201 and the first probe 3D fine adjustment stage 202 are locked in place by the first locking device 205, and the second probe 3D coarse adjustment stage 401 and the second probe 3D fine adjustment stage 402 are locked in place by the second locking device 405. The locking device uses a magnetic powder brake, which achieves gradual locking by progressively applying current, avoiding impact and displacement during the locking process. Throughout the locking process, the two fine adjustment stages continuously perform micro-scans and cooperate with feedback control to complete the final locking of the probe's spatial position.

[0060] The same adjustment, scanning, and locking process is repeated on the other probe, and the two probes are locked together. The probe gap is controlled between 1 nm and 20 nm to form a stable tunneling current 102.

[0061] This alignment method utilizes the exponential sensitivity of the tunneling current 102 itself as the alignment criterion, eliminating the need for an external optical alignment system and achieving nanoscale self-alignment. The progressive locking of the magnetic powder actuator, combined with the feedback from the fine-tuning stage, ensures that the aligned positional accuracy is not lost during the locking process. Example 1

[0062] The fiber single-section profile was inspected as follows: As attached Figure 5 As shown in the figure, this embodiment illustrates a method for detecting the cross-sectional profile of a fiber.

[0063] The sample to be tested, 304, is a fiber with a diameter of less than 2 nm, and is held from both ends by the first rotating device 303 and the second rotating device 305.

[0064] The first sample 3D coarse adjustment stage 301 and the second sample 3D coarse adjustment stage 307 synchronously transport the fiber to its initial position. When the fiber is near the outer edge of the tunneling current 102 region, the tunneling current 102 between the probes remains at a normal value. The first sample 3D fine adjustment stage 302 and the second sample 3D fine adjustment stage 306 move the fiber upward along the Z-axis, and the fiber gradually enters the area between the two probes. When the fiber blocks the tunneling path, the tunneling current 102 returns to zero, and the system records this point. The fiber continues to be moved upward in small increments until it leaves the tunneling area, the tunneling current 102 recovers, and the point is recorded again. The Z-axis movement distance between the two points is the radial dimension of the fiber cross-section at that angle.

[0065] After the measurement in a single direction is completed, the first sample three-dimensional coarse adjustment stage 301, the first sample three-dimensional fine adjustment stage 302, the second sample three-dimensional fine adjustment stage 306, and the second sample three-dimensional coarse adjustment stage 307 remain stationary. The first rotating device 303 and the second rotating device 305 synchronously drive the fiber to rotate at a fixed angle (e.g., 10 degrees). Then, the first sample three-dimensional fine adjustment stage 302 and the second sample three-dimensional fine adjustment stage 306 drive the fiber to move from top to bottom, repeating the current on / off measurement steps, and measuring the radial dimension of the cross section at that rotation angle.

[0066] After each set of measurements, the fiber is rotated by a fixed angle, and the measurement is repeated multiple times. When the fiber has rotated a total of 360 degrees, the measured dimensions corresponding to all angles are summarized, and each measuring point is marked on the coordinate system. The fiber cross-section is not necessarily a standard circle, and each measured value corresponds to a boundary point of the cross-section contour. By connecting all measuring points with a smooth curve, the complete contour of a single cross-section of the fiber can be obtained.

[0067] The core advantage of this method lies in the fact that the sample rotates within the tunneling gap between the two probes, allowing the tunneling electron beam to pass through the sample's interior. This yields the true profile of the sample's internal cross-section, rather than its surface morphology. This is a capability that existing STM and AFM methods cannot achieve—in current technologies, the sample is located outside the probes, making it impossible to perform transmission-type cross-sectional measurements by "rotating through the electron beam."

[0068] Overall measurement of fiber three-dimensional shape After a single cross-section measurement is completed, the first sample 3D fine-tuning stage 302 and the second sample 3D fine-tuning stage 306 move the fiber along its own length by a set step distance (e.g., 0.01 nm), repeating the full-circumference rotation measurement to obtain the cross-sectional profile at the next position. The cross-sectional curves corresponding to all step distances within the specified length of the fiber under test are sequentially acquired, and all cross-sectional profiles are continuously stitched together in three-dimensional space to reconstruct the outer surface of that section of the fiber, thus obtaining the complete three-dimensional morphology and all geometric dimensions of the fiber under test. Example 2

[0069] Device with environmental isolation like Figure 6 and Figure 7 As shown, this embodiment provides a complete dual-probe tunneling electron beam transmission detection device, including an environmental isolation cavity 5 and a vibration isolation platform 6.

[0070] Depending on the characteristics of the sample to be tested and the measurement requirements, the environmental isolation chamber 5 can be equipped with one of the following three working media: (1) Vacuum environment: The environmental isolation chamber 5 is a stainless steel vacuum chamber, equipped with a molecular pump and an ion pump, with a vacuum degree better than 10⁻ 5 Pa is suitable for transmission detection of solid samples and can minimize the scattering of the tunneling electron beam by gas molecules and the contamination of the probe surface.

[0071] (2) Non-conductive gas environment: The environmental isolation chamber 5 is filled with an inert gas (such as high-purity nitrogen or argon) with a gas conductivity of not more than 10⁻¹. 0 The gas pressure is adjustable from 10⁻² Pa to atmospheric pressure (S / m). The non-conductive gas environment is suitable for scenarios requiring protection against sample oxidation or for detection under near-atmospheric pressure conditions.

[0072] (3) Non-conductive liquid environment: The environmental isolation chamber 5 is filled with a non-conductive liquid (such as high-purity insulating oil or non-polar organic solvent), and the liquid conductivity is not greater than 10⁻ 6 S / m. The non-conductive liquid environment is particularly suitable for in-situ transmission detection of biomolecules (such as DNA and proteins), allowing direct observation of the three-dimensional structure of molecules under near-physiological conditions without the need for sample drying or fixation. Furthermore, the electron beam does not apply physical contact force to the sample, avoiding irreversible damage to biological tissues caused by the AFM tapping mode.

[0073] The vibration isolation platform 6 is an air-floating vibration isolation platform with a natural frequency below 3Hz, which can effectively isolate the influence of external vibration on the stability of the probe spacing. The environmental isolation cavity 5 is installed on the vibration isolation platform 6.

[0074] All electrical connections are introduced to the outside of the environmental isolation chamber 5 through a sealed feedthrough. The bias power supply 105, current detector, and signal processor 106 are located outside the environmental isolation chamber 5. Example 3

[0075] Direct measurement of insulating samples This embodiment illustrates the unique ability of the present invention to directly measure insulating samples without the need for plating.

[0076] The sample to be tested is a polytetrafluoroethylene (PTFE) film, approximately 10 nm thick, a typical insulating material. In existing STM technology, such insulating samples must first be coated with a conductive film (such as a gold film, approximately 5 nm thick) before tunneling measurements can be performed. However, a 5 nm thick coating significantly alters the surface morphology and micro / nano structure of the 10 nm thick PTFE film, and the measurement results cannot reflect the true structure of the sample.

[0077] Using the apparatus of this invention, a PTFE film is placed in the tunneling gap between two probes, acting solely as a shield for the electron beam and not participating in the conductive circuit, thus requiring no conductive coating. When the electron beam is blocked by the PTFE film, the current is interrupted; when it is not blocked, the current flows normally. The signal processor 106 obtains the thickness and cross-sectional information of the film by detecting the current transition position. The measurement results reflect the true structure of the PTFE film and are unaffected by any coating.

[0078] This embodiment demonstrates a significant difference between the present invention and the prior art: existing STM and tip-to-tip imaging devices follow the technical route of STM, requiring the sample to be conductive or have a conductive layer deposited on its surface. The present invention, however, has no requirement for sample conductivity and can directly measure insulating samples. This effect is something that those skilled in the art could not reasonably foresee after reading the prior art.

[0079] This invention addresses the problem of non-contact transmission detection of the internal structure of a material by introducing a shielding mechanism. The sample is actively placed in the electron beam path between two probes, acting as a shield and not participating in the conductive circuit. The tunneling electron beam is the active detection tool, and its shielding by the sample is precisely the working state required for detection. The material boundary is determined by detecting the switching on and off of the current (digital quantity). There are no requirements for the conductivity of the sample, allowing direct measurement of insulating samples. The sample is located in the tunneling gap between the two probes and can be rotated 360 degrees by a rotating device, allowing the sample to pass through the electron beam at different angles and obtain a complete cross-sectional profile of the sample's interior.

[0080] This invention is not limited to the above embodiments. Based on the technical solutions disclosed herein, those skilled in the art can make some substitutions and modifications to some of the technical features without creative effort, and all such substitutions and modifications are within the protection scope of this invention.

Claims

1. A dual-probe tunneling electron beam transmission detection device, characterized in that: It includes a base plate, on which a first probe assembly and a second probe assembly are symmetrically arranged, and a sample delivery mechanism is arranged between the two sets of probe assemblies. The first probe assembly includes a first nanoprobe having a first tip; The second probe assembly includes a second nanoprobe with a second tip, the second tip being disposed opposite to the first tip, and a tunneling gap being formed between them; A bias power supply is connected between the first nanoprobe and the second nanoprobe to apply a bias voltage between the two probes to generate a tunneling electron beam in the tunneling gap. A current detector is also connected in series between the first nanoprobe and the second nanoprobe to detect the tunneling current flowing between the first nanoprobe and the second nanoprobe. The current detector is connected to the signal processor and is used to obtain the internal structure information of the sample under test based on the changes in the on / off state of the tunneling current. The changes in the on / off state of the tunneling current include the interruption of the current when the tunneling electron beam is blocked by the sample under test and the normal flow of the current when it is not blocked.

2. The dual-probe tunneling electron beam transmission detection device according to claim 1, characterized in that: The first probe assembly also includes a first probe three-dimensional coarse adjustment stage, a first probe three-dimensional fine adjustment stage is provided on the first probe three-dimensional coarse adjustment stage, a first probe support base is provided on the first probe support base, a first probe support is provided on the first probe support base, a first nanoprobe is installed at the end of the first probe support, a first locking device is provided on the first probe support, and the first locking device is provided on the first locking device base. The second probe assembly also includes a second probe three-dimensional coarse adjustment stage, a second probe three-dimensional fine adjustment stage, a second probe support base, a second probe support on the second probe support base, a second nanoprobe installed at the end of the second probe support, and a second locking device on the second probe support, which is located on the second locking device base.

3. The dual-probe tunneling electron beam transmission detection device according to claim 2, characterized in that: The sample transport mechanism includes a first three-dimensional coarse adjustment worktable and a second three-dimensional coarse adjustment worktable for a sample. A first three-dimensional fine adjustment worktable for a sample is provided on the first three-dimensional coarse adjustment worktable for a sample, and a first rotating device is provided on the first three-dimensional fine adjustment worktable for a sample. The second sample three-dimensional coarse adjustment worktable is equipped with a second sample three-dimensional fine adjustment worktable, and a second rotating device is provided on the second sample three-dimensional fine adjustment worktable. The first rotating device and the second rotating device are symmetrically arranged, and the first rotating device and the second rotating device cooperate with each other to clamp the same sample to be tested.

4. The dual-probe tunneling electron beam transmission detection device according to claim 3, characterized in that: The first probe assembly, the second probe assembly, the sample delivery mechanism, and the base plate are all located within an environmental isolation chamber, and the medium within the environmental isolation chamber is any one of vacuum, non-conductive gas, or non-conductive liquid.

5. The dual-probe tunneling electron beam transmission detection device according to claim 4, characterized in that: When the medium is a non-conductive gas, its conductivity is no greater than 10. -10 S / m; when the medium is a non-conductive liquid, its conductivity is not greater than 10. -6 S / m; The medium is vacuum, and the vacuum level inside the environmental isolation chamber is no greater than 10. -4 Pa.

6. The dual-probe tunneling electron beam transmission detection device according to claim 5, characterized in that: The environmental isolation cavity is installed on the vibration isolation platform, and the natural frequency of the vibration isolation platform is no greater than 5Hz.

7. The dual-probe tunneling electron beam transmission detection device according to claim 1, characterized in that: The radius of curvature of the first and second tips is no greater than 50 nm, and the distance between the first and second tips is 1 nm to 20 nm.

8. The dual-probe tunneling electron beam transmission detection device according to claim 2, characterized in that: Both the first and second locking devices are magnetic powder brakes.

9. A dual-probe tunneling electron beam alignment and transmission detection method, characterized in that: The dual-probe tunneling electron beam transmission detection device according to any one of claims 1-8 includes the following: S1. The first tip of the first nanoprobe and the second tip of the second nanoprobe are positioned opposite each other so that the two tips are roughly facing each other. S2. Drive the second nanoprobe to scan point by point in the XY plane, where the Z-axis direction is the direction of the line connecting the two tips. Detect the tunneling current between the two probes at each scanning point and record the XY position corresponding to the maximum value of the tunneling current. S3. Lock the second nanoprobe at the XY position corresponding to the maximum value of the tunneling current to complete the alignment of the two tips in the XY plane; S4. Adjust the distance between the two tips to the target working distance via Z-axis feed, and lock the Z-axis position; S5. Apply a bias voltage between the two probes to generate a stable tunneling electron beam between the two tips and detect the initial tunneling current. S6. The sample to be tested is transported to the tunneling gap between the first tip and the second tip, so that the sample to be tested is placed on the transmission path of the tunneling electron beam. The sample to be tested does not participate in the conductive circuit, but only acts as a shield for the tunneling electron beam. When the tunneling electron beam is shielded by the sample to be tested, the tunneling current is interrupted. When the tunneling electron beam is not shielded, the tunneling current flows normally. S7. Detect the change in the on / off state of the tunneling current. When the current drops sharply from the normal value to zero, record the position as the shielding boundary of the sample. When the current returns to normal from zero, record the position as the other side boundary of the sample. The distance between the two jump points is the radial dimension of the sample under test in that direction. S8. Drive the sample to be tested to rotate around its own axis by a fixed angle through the first rotating device and the second rotating device. Perform Z-direction scanning detection again at this rotation angle, that is, repeat the operation of step S7 to obtain the radial dimension of the sample to be tested at this rotation angle. S9. Repeat step S8 until the sample under test has rotated a total of 360 degrees. Summarize the radial dimension data corresponding to all rotation angles, mark each measuring point in the coordinate system, and connect all measuring points with a smooth curve to reconstruct the cross-sectional profile of the sample under test.

10. The dual-probe tunneling electron beam alignment and transmission detection method according to claim 9, characterized in that: After the measurement of a single cross-sectional profile is completed, move along the length direction of the sample to be tested by a set step distance, and repeat steps S8 and S9 to obtain the cross-sectional profile of the next position; sequentially collect the cross-sectional profiles corresponding to all step distances within the specified length, and stitch all cross-sectional profiles together in three-dimensional space to reconstruct the three-dimensional morphology of the sample to be tested.

Images