Microwave impedance microscope

Abstract

The invention discloses a microwave impedance microscope, which relates to the technical field of scanning probe microscopes and comprises an antenna module, a probe module, a scanning tube and a displacement module. The probe module adopts an STM probe, and an insulating layer and a metal coating are sequentially arranged on the outer side of a tungsten tip of the STM probe to form a coaxial structure so as to localize signals. The antenna module is arranged on the periphery of the STM probe and can maintain relatively stable output power within a predetermined frequency band. Through cooperative work of the broadband antenna and the STM probe, broadband measurement can be achieved without repeated hardware matching, it is ensured that data references of different frequencies are consistent, and quantitative comparison analysis is supported. The STM probe structure effectively eliminates stray capacitance of a traditional AFM cantilever, so that the signal height is localized to the tip, and the spatial resolution and the measurement accuracy are remarkably improved.

Description

Technical Field

[0001] This invention relates to the field of scanning probe microscopy, and in particular to a microwave impedance microscope. Background Technology

[0002] Microwave Impedance Microscopy (MIM) is a key scanning probe technique that characterizes the electrical properties of materials at the nanoscale and is widely used in modern materials research. A typical MIM system couples a microwave signal to the sample using a metallized probe and detects the amplitude and phase of the reflected signal, thereby generating a two-dimensional image corresponding to the sample's resistance and capacitance characteristics.

[0003] However, existing systems are typically optimized for specific frequencies, resulting in limited effective operating bandwidth. When performing broadband measurements, impedance matching needs to be re-performed for different frequencies, a cumbersome and inefficient process that makes direct quantitative comparison of data from different frequencies difficult. Furthermore, existing MIM systems generally use AFM (atomic force microscope) probes as the carrier of microwave signals, which inherently limit their spatial resolution. The metallized conical tip and cantilever structure of the AFM probe introduce significant parasitic capacitances. These nonlocal electromagnetic couplings "drowsed" local signals from the tip region, leading to a decrease in the spatial resolution of the final image. Summary of the Invention

[0004] The main objective of this invention is to provide a microwave impedance microscope that aims to improve resolution and adapt to a wider frequency range.

[0005] To achieve the above objectives, the present invention provides a microwave impedance microscope comprising: The antenna module and probe module, wherein the probe module includes an STM probe, the antenna module is located around the STM probe, and the antenna module maintains a relatively stable output power within a predetermined frequency band; The STM probe includes a tungsten tip, and an insulating layer and a metal plating layer are sequentially provided on the tungsten tip outwards. The insulating layer is used to isolate the tungsten tip and the metal plating layer. The probe module is fixedly connected to the scanning tube; The displacement module is connected to the scanning tube and is used to adjust the position of the STM probe relative to the sample.

[0006] In one embodiment, the antenna module includes a substrate, a feed port, a feed line, and a plurality of antenna elements; The feed port is used to connect a coaxial cable; Multiple antenna elements are arranged on the substrate according to a planar logarithmic periodic pattern. The feed line is used for signal transmission and impedance matching is performed between the antenna elements and the feed port.

[0007] In one embodiment, the probe module further includes a PCB board, a probe tip holder, and a connecting part; The PCB board is electrically connected to the STM probe and the antenna module, and the probe tip holder is used to mount the STM probe and the PCB board. The needle tip holder and the connecting part are fixedly connected, and the needle tip holder is fixedly connected to the scanning tube through the connecting part.

[0008] In one embodiment, the microwave impedance microscope further includes a sample tray and a scanning head tray, the sample tray and the scanning head tray being fixedly connected; The displacement module includes a Z-direction adjustment component, an X-direction adjustment component, and a Y-direction adjustment component; The displacement module is fixedly connected to the scanning head tray, and the scanning tube is connected to the Z-direction adjustment component to drive the scanning tube to adjust in the Z-direction. The Y-direction adjustment component is fixedly connected to the sample stage, and the Y-direction adjustment component is fixedly connected to the X-direction adjustment component. The X-direction adjustment component is fixedly connected to the sample tray, so as to drive the sample stage to be adjusted in the X and Y directions.

[0009] In one embodiment, the X-direction adjustment assembly includes a first base, a first sliding stage, and a first piezoelectric ceramic stack; The first base is fixedly connected to the sample tray, and the first sliding stage is connected to the first base through the first piezoelectric ceramic stack to drive the first sliding stage to move relative to the first base in the X direction; The Y-direction adjustment assembly includes a second base, a second sliding stage, and a second piezoelectric ceramic stack. The second base is fixedly connected to the first sliding stage, and the second sliding stage is connected to the first base through the second piezoelectric ceramic stack to drive the second sliding stage to move relative to the second base in the Y direction. The sample stage is fixedly connected to the second sliding stage.

[0010] In one embodiment, the X-direction adjustment assembly further includes a first adjustment part, which and the first piezoelectric ceramic stack together clamp the first sliding stage; The first adjustment part is connected and fixed to the first base through the first connector. Adjusting the first connector can make the first adjustment part move closer to or further away from the first piezoelectric ceramic stack, so as to adjust the preload of the first sliding table on the first piezoelectric ceramic stack. The Y-direction adjustment assembly further includes a second adjustment part, which and the second piezoelectric ceramic stack together clamp the second sliding stage; The second adjustment part is connected and fixed to the second base through the second connector. Adjusting the second connector can make the second adjustment part move closer to or further away from the second piezoelectric ceramic stack, so as to adjust the preload of the second sliding table on the second piezoelectric ceramic stack.

[0011] In one embodiment, the first base is provided with two first support surfaces that are inclined to each other, and the two first piezoelectric ceramic stacks are respectively vertically disposed on the two first support surfaces; Both of the first support surfaces are parallel to the X direction to prevent the first sliding table from moving along the Y direction; The second base has two mutually inclined second support surfaces, and the two second piezoelectric ceramic stacks are respectively vertically arranged on the two second support surfaces; Both of the second support surfaces are parallel to the Y direction to prevent the first sliding stage from moving along the X direction.

[0012] In one embodiment, the Z-direction adjustment assembly includes a support housing and a third piezoelectric ceramic stack; The support housing is fixedly connected to the scanning head tray, the scanning tube is located inside the support housing, and a plurality of third piezoelectric ceramic stacks are spaced apart around the scanning tube to clamp and fix the scanning tube. The third piezoelectric ceramic stack is fixedly connected to the support housing to drive the scanning tube to move along the Z direction.

[0013] In one embodiment, the Z-direction adjustment assembly further includes a third adjustment section, and at least one of the third piezoelectric ceramic stacks is fixedly connected to the support housing through the third adjustment section; The third adjustment section is used to adjust the preload of the scanning tube on the third piezoelectric ceramic stack.

[0014] In one embodiment, a plurality of copper parts and magnets are spaced apart around the sample tray, and the copper parts and magnets cooperate to achieve magnetic damping and shock absorption; The scanning head tray is fixedly connected to multiple shock-absorbing springs to suspend the scanning head tray and reduce the transmission of external vibrations.

[0015] The technical solution of this invention constructs a wideband signal coupling and detection platform by combining the antenna module, which maintains relatively stable output power within a predetermined frequency band, with the STM probe. This allows the system to perform measurements directly over a wide frequency range without hardware readjustment, ensuring that data acquired at different frequency points have a consistent benchmark. This enables direct and reliable quantitative comparison and analysis. The special structure of the STM probe eliminates the nonlocal electromagnetic coupling caused by the AFM cantilever. The signal mainly interacts with the sample through the extremely localized region at the very tip of the STM probe, maximally suppressing the interference of parasitic capacitance to improve resolution. Attached Figure Description

[0016] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on the structures shown in these drawings without creative effort.

[0017] Figure 1 A schematic diagram of a structure of an embodiment of the microwave impedance microscope provided by the present invention; Figure 2 This is a schematic diagram of the STM probe structure; Figure 3 This is a schematic diagram of the antenna module. Figure 4 Figure 1 A magnified view of a section at point A in the middle; Figure 5 This is a schematic diagram of the assembly structure of the X-direction adjustment component and the Y-direction adjustment component; Figure 6 This is a schematic diagram of the assembly structure of the first adjustment section; Figure 7 This is a schematic diagram of the Z-direction adjustment component; Figure 8 This is a simulation diagram of the reflection coefficient.

[0018] Explanation of icon numbers: 11. Substrate; 12. Feed port; 13. Feed line; 14. Antenna vibrator; 2. Probe module; 21. STM probe; 211. Tungsten tip; 212. Insulating layer; 213. Metal plating; 22. PCB board; 23. Tip holder; 24. Connector; 3. Scan tube; 41. Z-direction adjustment assembly; 411. Support housing; 4111. Limiting groove; 412. Third piezoelectric ceramic stack; 413. Third adjustment part; 4131. Third spring; 4132. Mounting block; 4133. Fifth sapphire ball; 414. Central prism; 4141. Limiting arm; 415. Cover plate; 42. X-direction adjustment assembly; 421. First 422. Base; 423. First sliding stage; 424. First piezoelectric ceramic stack; 425. First adjustment part; 4241. First spring; 4242. First sliding plate; 4243. First sapphire ball; 4244. Second sapphire ball; 425. First support surface; 43. Y-direction adjustment assembly; 431. Second base; 432. Second sliding stage; 433. Second piezoelectric ceramic stack; 434. Second adjustment part; 4341. Second spring; 4342. Second sliding plate; 435. Second support surface; 44. Sample stage; 5. Sample tray; 51. Copper part; 6. Scanning head tray; 61. Shock-absorbing spring; 7. Sapphire sheet; 8. Hub.

[0019] The realization of the objective, functional features and advantages of the present invention will be further explained in conjunction with the embodiments and with reference to the accompanying drawings. Detailed Implementation

[0020] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0021] It should be noted that if the embodiments of the present invention involve directional indicators (such as up, down, left, right, front, back, etc.), the directional indicators are only used to explain the relative positional relationship and movement of the components in a specific posture. If the specific posture changes, the directional indicators will also change accordingly.

[0022] Furthermore, if the embodiments of this invention involve descriptions such as "first" or "second," these descriptions are for descriptive purposes only and should not be construed as indicating or implying their relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined with "first" or "second" may explicitly or implicitly include at least one of those features. Additionally, the use of "and / or" or "and / or" throughout the text includes three parallel solutions. For example, "A and / or B" includes solution A, solution B, or a solution where both A and B are satisfied simultaneously. Furthermore, the technical solutions of the various embodiments can be combined with each other, but this must be based on the ability of those skilled in the art to implement them. When the combination of technical solutions is contradictory or impossible to implement, it should be considered that such a combination of technical solutions does not exist and is not within the scope of protection claimed by this invention.

[0023] Microwave Impedance Microscopy (MIM) is a key scanning probe technique that characterizes the electrical properties of materials at the nanoscale and is widely used in modern materials research. A typical MIM system couples a microwave signal to the sample using a metallized probe and detects the amplitude and phase of the reflected signal, thereby generating a two-dimensional image corresponding to the sample's resistance and capacitance characteristics.

[0024] However, existing systems are typically optimized for specific frequencies, resulting in limited effective operating bandwidth. When performing broadband measurements, impedance matching needs to be re-performed for different frequencies, a cumbersome and inefficient process that makes direct quantitative comparison of data from different frequencies difficult. Furthermore, existing MIM systems generally use AFM (atomic force microscope) probes as the carrier of microwave signals, which inherently limit their spatial resolution. The metallized conical tip and cantilever structure of the AFM probe introduce significant parasitic capacitances. These nonlocal electromagnetic couplings "drowsed" local signals from the tip region, leading to a decrease in the spatial resolution of the final image.

[0025] It should be noted that the MIM system mainly consists of a microwave probe, a microwave signal source, an RF matching circuit, a microwave detection module, and a control and imaging system. The microwave probe is used to transmit and receive microwave signals and requires impedance matching with the vacuum. The RF matching circuit is used to connect the microwave signal source and the microwave probe to realize the injection of microwave signals and the extraction of reflected signals. The microwave detection module is used to demodulate the amplitude and phase of the reflected signals and output them to the data acquisition system. The control and imaging system is used to synchronously control the scanning, acquisition, and generation of two-dimensional electrical images.

[0026] Microwave signals are transmitted to a microwave probe via an RF cable and coupled to the sample surface. A local microwave impedance network is formed between the microwave probe and the sample. The conductivity and dielectric constant of different regions of the sample affect the reflection characteristics of the microwave signal. The reflected signal is decomposed into real and imaginary parts by a detector, corresponding to the resistive and capacitive properties of the sample. By scanning, the system can obtain a two-dimensional electrical distribution map of the sample surface.

[0027] Most existing commercial MIM devices are based on AFM tips. However, the parasitic capacitance of the tip cone and cantilever of AFM inevitably affects the microwaves, resulting in a decrease in resolution. Compared with the mechanical contact / near-field capacitive coupling of AFM, the tunneling current between the STM tip and the sample surface has higher lateral resolution and more localized coupling.

[0028] This invention proposes a microwave impedance microscope.

[0029] Please see Figures 1 to 8 In one embodiment of the present invention, the microwave impedance microscope includes: The antenna module and probe module 2, wherein the probe module 2 includes an STM probe 21, the antenna module is located around the STM probe 21, and the antenna module maintains a relatively stable output power within a predetermined frequency band. The STM probe 21 includes a tungsten tip 211, and the tungsten tip 211 is provided with an insulating layer 212 and a metal plating layer 213 in sequence. The insulating layer 212 is used to isolate the tungsten tip 211 and the metal plating layer 213. The probe module 2 is fixedly connected to the scanning tube 3; The displacement module is connected to the scanning tube 3 and is used to adjust the position of the STM probe 21 relative to the sample. The technical solution of this invention constructs a wideband signal coupling and detection platform by combining the antenna module, which maintains a relatively stable output power within a predetermined frequency band, with the STM probe 21. This allows the system to perform measurements directly within a wide frequency range without hardware readjustment, ensuring that data acquired at different frequency points have a consistent benchmark. This enables direct and reliable quantitative comparison and analysis. The special structure of the STM probe 21 eliminates the nonlocal electromagnetic coupling caused by the AFM cantilever. The signal mainly interacts with the sample through the extremely localized region at the very tip of the STM probe 21, maximally suppressing the interference of parasitic capacitance to improve resolution.

[0030] The predetermined frequency band range is a frequency band range greater than 2 GHz, and within the frequency band range greater than 2 GHz, the antenna module maintains a relatively stable output power.

[0031] Furthermore, using tunneling current as a feedback signal, since tunneling current is more localized than atomic force, the antenna module can be closer to the sample surface, improving the localization of microwave coupling and thus increasing resolution.

[0032] like Figure 2 As shown, by sequentially wrapping the insulating layer 212 and the metal plating layer 213 around the tungsten tip 211, the tungsten tip 211, the insulating layer 212, and the metal plating layer 213 constitute a miniature coaxial antenna, forming a continuous impedance transmission structure from a macroscopic coaxial cable to a nanoscale tip. This coaxial structure provides an efficient, shielded transmission path for microwave signals from the antenna to the localized region at the very tip of the tip, greatly reducing spatial diffusion and energy loss during transmission. It also eliminates the large parasitic capacitance introduced by the metallized cantilever in traditional AFM-MIM. This allows the detection signal to originate almost entirely from the extremely localized interaction between the tip of the STM probe 21 and the sample, thereby improving spatial resolution.

[0033] Preferably, the insulating layer 212 is aluminum oxide and the metal plating layer 213 is gold.

[0034] like Figure 3 As shown, the antenna module includes a substrate 1, a feed port 12, a feed line 13, and multiple antenna elements 14; The feed port 12 is used to connect a coaxial cable; Multiple antenna elements 14 are arranged on the substrate 1 according to a planar logarithmic periodic pattern. The feed line 13 is used for signal transmission and impedance matching is performed between the antenna elements 14 and the feed port 12.

[0035] It should be noted that the antenna module adopts a planar log-periodic antenna array design, integrating multiple antenna elements 14 on the substrate 1 according to a specific pattern to form a mature broadband antenna, ensuring relatively stable output power and forming a continuous and wide operating bandwidth.

[0036] It is understood that the feed port 12 is the connection port between the antenna element 14 and the coaxial cable of the signal source, and simultaneously performs impedance matching between the antenna element 14 and the coaxial cable.

[0037] The antenna element 14 converts the microwave signal input from the feed port 12 into electromagnetic wave radiation space.

[0038] Furthermore, this allows the antenna module to achieve stable impedance matching with the vacuum without any external tuning over an extremely wide frequency range greater than 2 GHz, while maintaining relatively stable output power. This solves the problem of traditional MIM systems requiring repeated impedance matching at different frequency points, not only improving the efficiency of broadband measurements by several orders of magnitude but also ensuring that all data across the entire frequency band is based on the same stable signal reference, thus enabling direct and reliable quantitative comparison and analysis.

[0039] like Figure 8 As shown, Figure 8 The graph shows the reflection coefficient. The horizontal axis represents the signal source output frequency, and the vertical axis represents the reflection coefficient. The smaller the reflection coefficient, the stronger the transmission and reception. It can be seen that microwave signals can be received over a wide range (greater than 2 GHz).

[0040] Optionally, the substrate 1 is made of ceramic.

[0041] like Figure 4 As shown, the probe module 2 also includes a PCB (Printed Circuit Board), a probe tip holder 23, and a connecting part 24; The PCB board 22 is electrically connected to the STM probe 21 and the antenna module, and the probe tip holder 23 is used to mount the STM probe 21 and the PCB board 22. The needle tip holder 23 and the connecting part 24 are fixedly connected, and the needle tip holder 23 is fixedly connected to the scanning tube 3 through the connecting part 24.

[0042] It is understood that the tip holder 23 provides a mounting reference for the STM probe 21 and the PCB board 22. The antenna module is integrated on the PCB board 22, ensuring that the relative position between the STM probe 21 and the antenna module remains accurate and stable. Furthermore, the connecting part 24 rigidly fixes the tip holder 23 and the scanning tube 3.

[0043] Optionally, the needle tip support 23 is fixedly connected to the connecting part 24 by screws, and the PCB board 22 is used to transmit microwave and tunneling current signals.

[0044] like Figure 1 and Figure 5 As shown, the microwave impedance microscope also includes a sample tray 5 and a scanning head tray 6, which are fixedly connected. The displacement module includes a Z-direction adjustment component 41, an X-direction adjustment component 42, and a Y-direction adjustment component 43; The displacement module is fixedly connected to the scanning head tray 6, and the scanning tube 3 is connected to the Z-direction adjustment component 41 to drive the scanning tube 3 to adjust in the Z-direction. The Y-direction adjustment component 43 is fixedly connected to the sample stage 44, and the Y-direction adjustment component 43 is fixedly connected to the X-direction adjustment component 42. The X-direction adjustment component 42 is fixedly connected to the sample tray 5, so as to drive the sample stage 44 to be adjusted in the X and Y directions.

[0045] It is understandable that the X, Y, and Z directions are three mutually perpendicular directions. Figure 5 The lower right corner is a reference coordinate added for easier explanation. This directional indicator is only used to explain the relative positional relationship and movement of the components in a specific posture. If the specific posture changes, the directional indicator will also change accordingly.

[0046] It is understood that the sample tray 5 and the scanning head tray 6 are rigidly fixedly connected to form a unified main frame, establishing a common and stable mechanical reference benchmark. The Z-direction adjustment component 41 is used to adjust the distance between the SMT probe and the sample, and the X-direction adjustment component 42 and the Y-direction adjustment component 43 are used to adjust the sample detection area.

[0047] Optionally, the X-direction adjustment assembly 42 includes a first base 421, a first sliding stage 422, and a first piezoelectric ceramic stack 423; The first base 421 is fixedly connected to the sample tray 5, and the first sliding stage 422 is connected to the first base 421 through the first piezoelectric ceramic stack 423 to drive the first sliding stage 422 to move relative to the first base 421 in the X direction. The Y-direction adjustment component 43 includes a second base 431, a second sliding stage 432, and a second piezoelectric ceramic stack 433; The second base 431 is fixedly connected to the first sliding stage 422. The second sliding stage 432 is connected to the first base 421 through the second piezoelectric ceramic stack 433 to drive the second sliding stage 432 to move relative to the second base 431 in the Y direction. The sample stage 44 is fixedly connected to the second sliding stage 432.

[0048] It should be noted that piezoelectric ceramic stacks, as the driving core, utilize their "stick-slip" working principle to achieve cross-scale motion. Within a single step, it can achieve fine stepping at the nanometer or even sub-nanometer level to meet the positioning requirements of high-resolution scanning; by continuously accumulating a large number of steps, it can also achieve large-scale movement at the millimeter or even centimeter level.

[0049] Understandably, the piezoelectric ceramic stack is directly integrated between the base and the sliding stage, forming a highly integrated electromechanical drive module. Compared to systems requiring external motors, drive belts, or long screws, this reduces intermediate transmission links, avoids errors, backlash, and wear, and improves displacement reliability and long-term repeatability. It also simplifies assembly and calibration processes.

[0050] It is understood that the X-direction adjustment component 42 and the Y-direction adjustment component 43 are stacked and connected, realizing the mechanical decoupling of the two horizontal directions of movement. Furthermore, the precision adjustment characteristics of the first piezoelectric ceramic stack 423 and the second piezoelectric ceramic stack 433 are utilized to improve the positioning accuracy.

[0051] Furthermore, a sapphire sheet 7 is provided between two adjacent piezoelectric ceramics in the piezoelectric ceramic stack. The sapphire sheet 7 can provide a suitable coefficient of friction, causing the adjacent piezoelectric ceramics to undergo "stick-slip" displacement, so as to achieve electronically controlled fine displacement.

[0052] Optionally, the X-direction adjustment component 42 further includes a first adjustment part 424, which together with the first piezoelectric ceramic stack 423 clamps the first sliding stage 422; The first adjustment part 424 is connected and fixed to the first base 421 through the first connector. Adjusting the first connector can make the first adjustment part 424 move closer to or further away from the first piezoelectric ceramic stack 423, so as to adjust the preload of the first sliding table 422 on the first piezoelectric ceramic stack 423. The Y-direction adjustment component 43 further includes a second adjustment part 434, which and the second piezoelectric ceramic stack 433 together clamp the second sliding stage 432. The second adjustment part 434 is connected and fixed to the second base 431 through the second connector. Adjusting the second connector can make the second adjustment part 434 move closer to or further away from the second piezoelectric ceramic stack 433, so as to adjust the preload of the second sliding table 432 on the second piezoelectric ceramic stack 433.

[0053] It should be noted that the first sliding stage 422 and the first piezoelectric ceramic stack 423 are in surface contact and are relatively fixed by static friction. If the friction is too small, the first sliding stage 422 will slide relative to the first piezoelectric ceramic stack 423, affecting the adjustment accuracy. The friction between the two can be adjusted by adjusting the preload of the first sliding stage 422 on the first piezoelectric ceramic stack 423. However, if the preload is too large, the first piezoelectric ceramic stack 423 may not be able to be driven.

[0054] To address this, adjustable first adjustment unit 424 and second adjustment unit 434 are provided, enabling the operator to actively and precisely control the preload between the piezoelectric ceramic stack and the sliding stage. This solves the core problem of extreme sensitivity to friction in "stick-slip" piezoelectric drives. By adjusting the preload, the coefficient of friction can be precisely set within the region of highest driving efficiency, ensuring that the piezoelectric ceramic stack can stably and reliably generate "stick-slip" motion. This avoids slippage (failure to drive) due to insufficient preload, as well as jamming or slow response due to excessive preload, ensuring that the displacement system always operates at its optimal state.

[0055] It is understandable that the relationship between the second sliding stage 432 and the second piezoelectric ceramic stack 433 is the same as above, and will not be repeated here.

[0056] Furthermore, the first adjustment part 424 includes a first spring 4241. Both ends of the first spring 4241 are fixed to the first base 421 through the first connector (not shown in the figure). The first connector is threaded to the first base 421 and abuts against the first spring 4241. The distance between the first spring 4241 and the first base 421 can be adjusted by rotating the first connector to adjust the preload. The first connector can be a bolt or the like. This embodiment does not impose any specific limitations on this.

[0057] Furthermore, the first adjustment unit 424 also includes a first sliding plate 4242, which is located between the first spring 4241 and the first sliding stage 422 and is held by the first spring 4241 and the first sliding stage 422. A plurality of first sapphire balls 4243 are provided between the first spring 4241 and the first sliding plate 4242, and both the first spring 4241 and the first sliding plate 4242 are provided with grooves for fixing the first sapphire balls 4243. The sapphire balls have small rolling friction to ensure the transmission of large positive pressure. The plurality of first sapphire balls 4243 are spaced apart along the X direction, and the extension direction of the first spring 4241 is perpendicular to the X direction to prevent the first sliding stage 422 from rotating and tilting around the Y direction. This ensures that the sliding stage maintains a strictly horizontal posture when moving in the X direction, avoiding unexpected tilting and shaking, thereby ensuring the stability of the sample stage 44 plane and providing a solid planar reference for high-precision scanning.

[0058] It should be noted that when the first sliding stage 422 moves relative to the first base 421, the first spring 4241, the first sliding plate 4242, and the first base 421 are relatively fixed, while the first sliding plate 4242 moves relative to the first sliding plate 4242.

[0059] like Figure 6 As shown, a second sapphire ball 4244 is provided between the first sliding plate 4242 and the first base 421, and both the first base 421 and the first sliding plate 4242 are provided with corresponding sliding grooves. The extension direction of the sliding groove is parallel to the X direction. The second sapphire ball 4244 is located in the sliding groove, ensuring that the first sliding plate 4242 can move freely while transmitting a large positive pressure.

[0060] It is understood that the second adjustment part 434 also includes a second spring 4341, a second sliding plate 4342, a third sapphire ball and a fourth sapphire ball, and its structure and function are similar to those of the first adjustment part 424, so they will not be discussed again here.

[0061] Optionally, the first reed 4241 and the second reed 4341 are beryllium copper reeds.

[0062] Optionally, the first base 421 is provided with two first support surfaces 425 that are inclined to each other, and the two first piezoelectric ceramic stacks 423 are respectively vertically disposed on the two first support surfaces 425. Both first support surfaces 425 are parallel to the X direction to prevent the first sliding table 422 from moving along the Y direction. The second base 431 is provided with two mutually inclined second support surfaces 435, and the two second piezoelectric ceramic stacks 433 are respectively vertically arranged on the two second support surfaces 435; Both of the second support surfaces 435 are parallel to the Y direction to prevent the first sliding table 422 from moving along the X direction.

[0063] Understandably, by setting two mutually inclined first support surfaces 425 on the first base 421 and vertically mounting two first piezoelectric ceramic stacks 423 on them respectively, a natural "V-shaped" guide mechanism is formed. Since both first support surfaces 425 are parallel to the X direction, the degree of freedom of movement of the first sliding stage 422 in the Y direction is restricted. Similarly, the "V-shaped" layout of the second base 431 prevents the second sliding stage 432 from moving in the X direction. Without the need for additional, complex linear guides or flexible hinges, motion crosstalk between the two horizontal directions is eliminated, ensuring the purity and accuracy of displacement.

[0064] like Figure 7 As shown, the Z-direction adjustment assembly 41 includes a support housing 411 and a third piezoelectric ceramic stack 412; The support housing 411 is fixedly connected to the scanning head tray 6, the scanning tube 3 is located inside the support housing 411, and a plurality of third piezoelectric ceramic stacks 412 are spaced apart on the periphery of the scanning tube 3 to clamp and fix the scanning tube 3. The third piezoelectric ceramic stack 412 is fixedly connected to the support housing 411 to drive the scanning tube 3 to move along the Z direction.

[0065] Understandably, by spaced out multiple third piezoelectric ceramic stacks 412 around the scanning tube 3 and driving the scanning tube 3 in a clamping and fixing manner, a symmetrical, compact, and highly rigid Z-axis driving structure is constructed. This ensures that the driving force is uniformly applied to the scanning tube 3, effectively suppressing any lateral drift or tilting that may occur during the Z-axis movement of the scanning tube 3, and guaranteeing that the distance between the STM probe 21 and the sample can be precisely controlled during the approach and scanning process.

[0066] Furthermore, the Z-direction adjustment assembly 41 also includes a third adjustment part 413, and at least one of the third piezoelectric ceramic stacks 412 is fixedly connected to the support housing 411 through the third adjustment part 413; The third adjustment unit 413 is used to adjust the preload of the scanning tube 3 on the third piezoelectric ceramic stack 412.

[0067] Understandably, the preload of at least one of the third piezoelectric ceramic stacks 412 can be precisely adjusted via the third adjustment unit 413. This allows the operator to perform fine mechanical calibration for the Z-axis drive, which demands the highest precision and stability. Through adjustment, the contact state between the scanning tube 3 and the third piezoelectric stack can be optimized, improving the accuracy, response speed, and stability of the Z-axis stepping.

[0068] Optionally, in some embodiments, multiple third piezoelectric ceramic stacks 412 located on different sides are fixedly connected to the support housing 411 via the third adjusting part.

[0069] In one embodiment, the number of the third piezoelectric ceramic stacks 412 is six, with each pair of the third piezoelectric ceramic stacks 412 forming a group. The three groups of the third piezoelectric ceramic stacks 412 are arranged at 120° intervals around the scanning tube 3. The third piezoelectric ceramic stacks 412 in the same group are arranged at intervals along the axial direction of the scanning tube 3 to ensure effective clamping of the scanning tube 3.

[0070] It is understood that the third piezoelectric ceramic stack 412 is similar to the first piezoelectric ceramic stack 423, and is provided with a sapphire sheet 7, which will not be discussed again here.

[0071] Furthermore, the third adjustment part includes a mounting block 4132 and a third spring 4131. The two ends of the third spring 4131 are fixed to the support housing 411 through a third connector (not shown in the figure). The third piezoelectric ceramic stack 412 is fixedly connected to the mounting block 4132. The third spring 4131 abuts against the side of the mounting block 4132 away from the third piezoelectric ceramic stack 412. The third connector is threaded to the support housing 411. By rotating the third connector, the preload of the scanning tube 3 on the third piezoelectric ceramic stack 412 can be adjusted. Optionally, the third connector is a bolt.

[0072] In some embodiments, a fifth sapphire ball 4133 is provided between the third spring 4131 and the mounting block 4132, and both the third spring 4131 and the mounting block 4132 are provided with grooves for mounting the fifth sapphire ball 4133.

[0073] Optionally, there may be multiple third springs 4131 to ensure the magnitude of the preload.

[0074] In some embodiments, the Z-direction adjustment assembly 41 further includes a central prism 414, which is sleeved on the scanning tube 3 and fixedly connected to the scanning tube 3. The scanning tube 3 is connected to the third piezoelectric ceramic stack 412 through the central prism 414. It can be understood that multiple third piezoelectric ceramic stacks 412 clamp the central prism 414 to indirectly clamp and fix the scanning tube 3.

[0075] Furthermore, the support housing 411 has a limiting groove 4111, and the central prism 414 extends outward with a limiting arm 4141. The limiting arm 4141 cooperates with the limiting groove 4111 to limit the maximum range of movement of the central prism 414 along the Z direction.

[0076] Optionally, the Z-direction adjustment assembly 41 further includes a cover plate 415, which is used to cover the side of the support housing 411 away from the sample stage 44 and can cooperate with the limiting slide groove 4111 to limit the maximum movement distance of the limiting arm 4141 away from the sample stage 44.

[0077] In some embodiments, the support housing 411 is provided with a plurality of hubs 8 spaced apart around its periphery, and each hub 8 is equipped with a plurality of copper electrodes.

[0078] Understandably, the drive circuits for the piezoelectric ceramic stack, the drive circuit for the scanning tube 3, and the microwave signal lines result in a large number of cables being concentrated inside the scanning head, making troubleshooting difficult once an error occurs. The function of the hub 8 is to make the scanning head more modular. If the problem is with the internal circuitry connected to the hub 8, the internal cables can be replaced; if the problem is with the external instrument connected to the hub 8, only the individual cables need to be replaced, not the entire head. Furthermore, the hub 8 itself makes the complex internal cabling easier to identify and manage.

[0079] like Figure 1 As shown, the sample tray 5 is provided with multiple copper parts 51 and magnets (not shown) at intervals around its perimeter. The copper parts 51 and the magnets cooperate to achieve magnetic damping and shock absorption. The scanning head tray 6 is fixedly connected to a plurality of shock-absorbing springs 61, which are used to suspend the scanning head tray 6 and reduce the transmission of external vibrations.

[0080] It should be noted that the copper component 51 arranged around the sample tray 5, combined with the magnet, constitutes an eddy current magnetic damper. When the system is subjected to low-frequency vibrations (such as ground vibrations or people walking), the magnet and the copper component 51 move relative to each other, generating eddy currents, thereby converting the mechanical energy of the vibration into heat energy and dissipating it.

[0081] Furthermore, by suspending the scanning head tray 6 using multiple damping springs 61, high-frequency vibrations from the platform and ground can be effectively isolated and attenuated, preventing them from being transmitted to core components. This reduces the absolute dependence on expensive and bulky external active vibration isolation platforms, improving the deployment flexibility and overall cost-effectiveness of the equipment.

[0082] Furthermore, it should be noted that existing commercial MIM modules are specially designed to achieve low temperatures, often resulting in complex structures, cumbersome operation, and high costs. Once the low-temperature equipment fails, it is difficult to maintain.

[0083] Commercial MIMs often include many low-temperature modules to meet low-temperature requirements, but these modules do not function when measuring at room temperature, only increasing costs and maintenance difficulty.

[0084] This invention simplifies processing costs and assembly difficulty, greatly increases experimental efficiency, and is suitable for room temperature environments. The simplified scanning head, due to its high modularity, also helps to reduce the overall vibration and noise of the instrument, achieving higher resolution.

[0085] The above description is merely an exemplary embodiment of the present invention and does not limit the scope of protection of the present invention. Any equivalent structural transformations made based on the technical concept of the present invention and the contents of the specification and drawings of the present invention, or direct / indirect applications in other related technical fields, are included within the scope of protection of the present invention.

Claims

1. A microwave impedance microscope, characterized in that, include: The antenna module and probe module, wherein the probe module includes an STM probe, the antenna module is located around the STM probe, and the antenna module maintains a relatively stable output power within a predetermined frequency band; The STM probe includes a tungsten tip, and an insulating layer and a metal plating layer are sequentially provided on the tungsten tip outwards. The insulating layer is used to isolate the tungsten tip and the metal plating layer. The probe module is fixedly connected to the scanning tube; The displacement module is connected to the scanning tube and is used to adjust the position of the STM probe relative to the sample.

2. The microwave impedance microscope as described in claim 1, characterized in that, The antenna module includes a substrate, a feed port, a feed line, and multiple antenna elements; The feed port is used to connect a coaxial cable; Multiple antenna elements are arranged on the substrate according to a planar logarithmic periodic pattern. The feed line is used for signal transmission and impedance matching is performed between the antenna elements and the feed port.

3. The microwave impedance microscope as described in claim 1, characterized in that, The probe module also includes a PCB board, a probe tip holder, and a connecting part; The PCB board is electrically connected to the STM probe and the antenna module, and the probe tip holder is used to mount the STM probe and the PCB board. The needle tip holder and the connecting part are fixedly connected, and the needle tip holder is fixedly connected to the scanning tube through the connecting part.

4. The microwave impedance microscope as described in claim 1, characterized in that, The microwave impedance microscope also includes a sample tray and a scanning head tray, which are fixedly connected. The displacement module includes a Z-direction adjustment component, an X-direction adjustment component, and a Y-direction adjustment component; The displacement module is fixedly connected to the scanning head tray, and the scanning tube is connected to the Z-direction adjustment component to drive the scanning tube to adjust in the Z-direction. The Y-direction adjustment component is fixedly connected to the sample stage, and the Y-direction adjustment component is fixedly connected to the X-direction adjustment component. The X-direction adjustment component is fixedly connected to the sample tray, so as to drive the sample stage to be adjusted in the X and Y directions.

5. The microwave impedance microscope as described in claim 4, characterized in that, The X-direction adjustment assembly includes a first base, a first sliding stage, and a first piezoelectric ceramic stack. The first base is fixedly connected to the sample tray, and the first sliding stage is connected to the first base through the first piezoelectric ceramic stack to drive the first sliding stage to move relative to the first base in the X direction; The Y-direction adjustment assembly includes a second base, a second sliding stage, and a second piezoelectric ceramic stack. The second base is fixedly connected to the first sliding stage, and the second sliding stage is connected to the first base through the second piezoelectric ceramic stack to drive the second sliding stage to move relative to the second base in the Y direction. The sample stage is fixedly connected to the second sliding stage.

6. The microwave impedance microscope as described in claim 5, characterized in that, The X-direction adjustment assembly further includes a first adjustment part, which and the first piezoelectric ceramic stack together clamp the first sliding stage; The first adjustment part is connected and fixed to the first base through the first connector. Adjusting the first connector can make the first adjustment part move closer to or further away from the first piezoelectric ceramic stack, so as to adjust the preload of the first sliding table on the first piezoelectric ceramic stack. The Y-direction adjustment assembly further includes a second adjustment part, which and the second piezoelectric ceramic stack together clamp the second sliding stage; The second adjustment part is connected and fixed to the second base through the second connector. Adjusting the second connector can make the second adjustment part move closer to or further away from the second piezoelectric ceramic stack, so as to adjust the preload of the second sliding table on the second piezoelectric ceramic stack.

7. The microwave impedance microscope as described in claim 5, characterized in that, The first base is provided with two first support surfaces that are inclined to each other, and the two first piezoelectric ceramic stacks are respectively vertically arranged on the two first support surfaces; Both of the first support surfaces are parallel to the X direction to prevent the first sliding table from moving along the Y direction; The second base has two mutually inclined second support surfaces, and the two second piezoelectric ceramic stacks are respectively vertically arranged on the two second support surfaces; Both of the second support surfaces are parallel to the Y direction to prevent the first sliding stage from moving along the X direction.

8. The microwave impedance microscope as described in claim 4, characterized in that, The Z-direction adjustment assembly includes a support housing and a third piezoelectric ceramic stack; The support housing is fixedly connected to the scanning head tray, the scanning tube is located inside the support housing, and a plurality of third piezoelectric ceramic stacks are spaced apart around the scanning tube to clamp and fix the scanning tube. The third piezoelectric ceramic stack is fixedly connected to the support housing to drive the scanning tube to move along the Z direction.

9. The microwave impedance microscope as described in claim 8, characterized in that, The Z-direction adjustment assembly further includes a third adjustment part, and at least one of the third piezoelectric ceramic stacks is fixedly connected to the support housing through the third adjustment part; The third adjustment section is used to adjust the preload of the scanning tube on the third piezoelectric ceramic stack.

10. The microwave impedance microscope as described in claim 4, characterized in that, The sample tray is provided with multiple copper parts and magnets at intervals around its perimeter. The copper parts and magnets work together to achieve magnetic damping and shock absorption. The scanning head tray is fixedly connected to multiple shock-absorbing springs to suspend the scanning head tray and reduce the transmission of external vibrations.

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