Nonlinear dielectric constant measuring system based on scanning nonlinear dielectric microscope

Abstract

The invention discloses a nonlinear dielectric constant measuring system based on a scanning nonlinear dielectric microscope, comprising: a probe, one end of which forms a micro capacitance Cs with the upper surface of a sample to be tested; the low-frequency signal module applies a low-frequency signal to the lower surface of the to-be-tested sample; the other end of the probe is connected with an LC resonance circuit in the probe module; the output end of a signal amplifier in the probe module is connected with a frequency modulation demodulator; the frequency modulation demodulator demodulates the frequency signal modulated by the probe module, removes a high-frequency carrier signal, inputs the demodulated signal into the lock-in amplifier, and detects, separates and amplifies a high-signal-to-noise-ratio signal by taking the frequency of a low-frequency signal applied to the sample to be tested as a reference frequency; according to the measurement system, the detection speed, the service life of the probe and the multi-material applicability can be remarkably improved, meanwhile, the thermal disturbance effect is inhibited, and a reliable solution is provided for accurate characterization of nano electronic devices.

Description

Technical Field

[0001] This invention relates to the field of traffic safety technology, specifically to a nonlinear dielectric constant measurement system based on a scanning nonlinear dielectric microscope. Background Technology

[0002] Scanning nonlinear dielectric microscopy (SNDM) is a highly sensitive and high-resolution tool for characterizing nanoscale dielectric materials. It adopts the principle of nonlinear dielectric response detection, which excites the second or higher harmonic signals of the material by applying a high-frequency electric field and combines it with lock-in amplification technology to achieve sub-nanometer resolution. This technology is widely used in fields such as domain structure observation of ferroelectric materials and carrier distribution analysis of semiconductor devices.

[0003] Traditional SNDM technology employs the following techniques: 1. High-frequency LC oscillator design: By optimizing the capacitive coupling between the probe and sample, the detection sensitivity is increased to 10⁻⁶. 22 F / √Hz; 2. Non-contact probe (NC-SNDM): Utilizing the cantilever resonance characteristics of atomic force microscopy (AFM) probes to reduce mechanical contact damage; 3. Time-resolved SNDM (tr-SNDM): Achieving nanosecond-level transient capacitance detection through femtosecond laser synchronous triggering technology; It is evident that traditional SNDM systems mostly use microwave frequency bands (1-10GHz) for signal processing, and their bandwidth limitations result in insufficient real-time data acquisition speed, making it difficult to capture ultrafast dynamic processes. Secondly, metal probes are prone to oxidation and wear under prolonged high-frequency electric fields, significantly shortening probe lifespan and affecting measurement stability. In addition, existing systems have low detection sensitivity for low dielectric constant materials (such as two-dimensional semiconductors and organic ferroelectrics), making it difficult to achieve accurate quantitative analysis.

[0004] Traditional SNDM technology solutions lead to the following technical problems: (1) Insufficient signal bandwidth: The signal processing capability of microwave band is limited, making it difficult to support GHz-level real-time imaging and restricting ultrafast process research; (2) Short probe life: Metal probes are prone to oxidation and wear under high-frequency electric fields, and their lifespan is usually less than 200 hours, resulting in increased maintenance costs; (3) Difficulty in detecting low dielectric materials: The signal-to-noise ratio for two-dimensional materials (such as MoS2) is less than 5dB, making it difficult to accurately analyze the carrier distribution; (4) Significant impact of thermal disturbance: Local temperature rise leads to a decrease in the stability of ferroelectric domains, and the long-term measurement error can reach more than 10%.

[0005] Moreover, as nanoelectronic devices develop towards higher frequencies and smaller sizes, the limitations of traditional SNDM in terms of signal processing speed, probe stability, and adaptability to multiple materials are becoming increasingly apparent.

[0006] Based on this, the purpose of this invention is to address the shortcomings of the prior art by providing a nonlinear dielectric constant measurement system based on scanning nonlinear dielectric microscopy. This system aims to overcome the technical bottlenecks of traditional SNDM and significantly improve detection speed, probe life, and applicability to multiple materials by integrating millimeter-wave signal processing and thermally assisted readout technology. At the same time, it suppresses thermal disturbance effects and provides a reliable solution for the accurate characterization of nanoelectronic devices. Summary of the Invention

[0007] To address the shortcomings of existing technologies, the present invention aims to provide a nonlinear dielectric constant measurement system based on scanning nonlinear dielectric microscopy. By integrating millimeter-wave signal processing and thermally assisted readout technology, it significantly improves detection speed, probe lifespan, and applicability to multiple materials, while suppressing thermal disturbance effects. This provides a reliable solution for the accurate characterization of nanoelectronic devices, thereby overcoming the limitations of traditional SNDM in terms of signal processing speed, probe stability, and applicability to multiple materials.

[0008] Specifically, the technical problem to be solved by the present invention is to address the shortcomings of the prior art. The present invention provides a nonlinear dielectric constant measurement system based on a scanning nonlinear dielectric microscope, comprising: a probe, a probe module, a low-frequency signal module, a frequency modulation demodulator, and a lock-in amplifier.

[0009] A tiny capacitor C is formed between one end of the probe and the upper surface of the sample to be tested. s .

[0010] The low-frequency signal module applies a low-frequency signal to the lower surface of the sample to be tested.

[0011] The probe module consists of an LC resonant circuit and a signal amplifier connected in series, and the other end of the probe is connected to the LC resonant circuit in the probe module.

[0012] The output of the signal amplifier in the probe module is connected to the frequency modulation demodulator; the output of the frequency modulation demodulator is connected to the lock-in amplifier.

[0013] The frequency demodulator demodulates the frequency signal modulated by the probe module, removes the high-frequency carrier signal, inputs the demodulated signal into the lock-in amplifier, and uses the frequency of the low-frequency signal applied to the sample under test as the reference frequency for detection, separating and amplifying to generate a high signal-to-noise ratio signal.

[0014] In one embodiment of the nonlinear dielectric constant measurement system based on scanning nonlinear dielectric microscopy according to the present invention, the probe is a gallium nitride (GaN) probe.

[0015] In one embodiment of the nonlinear dielectric constant measurement system based on scanning nonlinear dielectric microscopy according to the present invention, the surface of the probe has a diamond coating.

[0016] In one embodiment of the nonlinear dielectric constant measurement system based on scanning nonlinear dielectric microscopy according to the present invention, an oxide film is formed on the surface of the probe, which can directly form a MOS structure with the sample to be tested.

[0017] In one embodiment of the nonlinear dielectric constant measurement system based on scanning nonlinear dielectric microscopy according to the present invention, the frequency of the high-frequency radio frequency signal generated by the LC resonant circuit is 0.5 GHz to 3.0 GHz.

[0018] In one embodiment of the nonlinear dielectric constant measurement system based on scanning nonlinear dielectric microscopy according to the present invention, the signal amplifier is a negative feedback amplifier.

[0019] In one embodiment of the nonlinear dielectric constant measurement system based on scanning nonlinear dielectric microscopy according to the present invention, a high signal-to-noise ratio signal is used as the output signal. The output signal can be used for the observation of strong dielectric polarization distribution, the ultra-high sensitivity measurement of charge distribution and impurity distribution in semiconductor devices, and the visualization of atomic bipolar torque using non-contact SNDM (scanning nonlinear dielectric microscopy).

[0020] In one embodiment of the nonlinear dielectric constant measurement system based on scanning nonlinear dielectric microscopy according to the present invention, a probe is installed at the end of a cantilever beam. When the probe approaches the sample surface, interatomic forces are generated, controlling the movement of the sample under test in the x and y directions to achieve scanning. A laser irradiates the back of the cantilever beam and is then reflected onto a four-quadrant photodetector to detect minute bending or deflection of the cantilever.

[0021] In one embodiment of the nonlinear dielectric constant measurement system based on scanning nonlinear dielectric microscopy according to the present invention, a high-frequency small signal is applied to the probe end, and the sample bottom electrode is grounded; a tiny MOS structure is formed between the probe and the sample; the nonlinear dielectric response of the ferroelectric material causes the capacitance to be slightly modulated with the bias voltage, and the signal generated by the above-mentioned slight modulation is extracted by a frequency demodulator and a lock-in amplifier; at each scanning point, the R (amplitude) or θ (phase) output of the lock-in amplifier is acquired, and the scanning position is saved one-to-one with the corresponding signal value; the two-dimensional signal intensity matrix is ​​mapped into a grayscale image or a pseudo-color image using software.

[0022] Compared with the prior art, the positive effects of the present invention are: the nonlinear dielectric constant measurement system based on scanning nonlinear dielectric microscopy proposed in this invention breaks through the resolution and sensitivity limits of traditional characterization methods by combining high-frequency nonlinear dielectric response detection with atomic-level probe technology.

[0023] The use of gallium nitride (GaN) probes with diamond coating extends probe life and expands signal processing bandwidth, enabling stronger real-time data acquisition capabilities. The GaN probes have a lifespan of over 1000 hours, which is significantly improved compared to traditional Pt probes (200 hours).

[0024] To address the issue that high-frequency electric fields may cause localized heating of the sample, leading to polarization state drift in ferroelectric materials, this invention employs laser pulses to locally heat the sample, increasing the nonlinear dielectric constant to 1000 times that of room temperature, while simultaneously triggering signal acquisition to avoid the accumulation of thermal disturbances.

[0025] The use of millimeter-wave signal processing enables imaging speeds of up to 3Gbps, which is 30 times faster than traditional SNDM (100Mbps).

[0026] To improve the detection sensitivity of low dielectric constant materials (such as two-dimensional semiconductors), an oxide film is formed on the probe surface, which directly forms a MOS structure with the sample to be tested, resulting in a wider range of measurable materials and greater ease of use. Attached Figure Description

[0027] Figure 1 This is a block diagram of the SNDM system structure in an embodiment of the present invention.

[0028] Figure 2 This is a schematic diagram illustrating the measurement of nonlinear dielectric constant in an embodiment of the present invention.

[0029] Figure 3 This is a schematic diagram illustrating the dielectric polarization measurement principle in an embodiment of the present invention.

[0030] Figure 4 This is a measurement example diagram of the probe in an embodiment of the present invention.

[0031] Figure 5 The image shows the SNDM measurement results when VPP=5mV in an embodiment of the present invention.

[0032] Figure 6 This is a graph showing the SNDM measurement results when VPP=10mV in an embodiment of the present invention.

[0033] Figure 7 This is a graph showing the SNDM measurement results when VPP=50mV in an embodiment of the present invention.

[0034] Figure 8This is a graph showing the SNDM measurement results when VPP=200mV in an embodiment of the present invention.

[0035] Figure 9 The graph shows the measurement results obtained by the AFM method.

[0036] Figure 10 This is a comparison chart of the measurement results obtained by the AFM method and the ferroelectric polarization distribution measurement results of the SNDM in the embodiments of the present invention. Detailed Implementation

[0037] Hereinafter, exemplary embodiments according to this application will be described in detail with reference to the accompanying drawings. Obviously, the described embodiments are merely some embodiments of this application, and not all embodiments of this application. It should be understood that this application is not limited to the exemplary embodiments described herein.

[0038] It is understood that the term "a" should be understood as "at least one" or "one or more," meaning that in one embodiment, the number of an element can be one, while in another embodiment, the number of the element can be multiple. The term "a" should not be construed as a limitation on the quantity. "Multiple" means two or more.

[0039] While ordinal numbers such as “first,” “second,” etc., will be used to describe various components, there is no limitation on which components are used herein. The term is used only to distinguish one component from another. For example, a first component may be referred to as a second component, and similarly, a second component may be referred to as a first component, without departing from the teachings of this application. The term “and / or” as used herein includes any and all combinations of one or more of the associated listed items.

[0040] The terminology used herein is for the purpose of describing various embodiments only and is not intended to be limiting. As used herein, the singular form also includes the plural form, unless the context clearly indicates otherwise. It will also be understood that the terms “comprising” and / or “having” as used in this specification specify the presence of the described features, numbers, operations, components, elements or combinations thereof, without excluding the presence or addition of one or more other features, numbers, operations, components, elements or combinations thereof.

[0041] The following is combined with Figure 1-4 The present invention will be further described with reference to specific embodiments.

[0042] Figure 1 shows a block diagram of the nonlinear dielectric constant measurement system based on scanning nonlinear dielectric microscopy in this invention, which includes: a probe, a probe module, a low-frequency signal module, a frequency modulation demodulator, and a lock-in amplifier.

[0043] A tiny capacitor C is formed between one end of the probe and the upper surface of the sample to be tested. s.

[0044] The low-frequency signal module applies a low-frequency signal to the lower surface of the sample to be tested.

[0045] The probe module consists of an LC resonant circuit and a signal amplifier connected in series, and the other end of the probe is connected to the LC resonant circuit in the probe module.

[0046] The output of the signal amplifier in the probe module is connected to the frequency modulation demodulator; the output of the frequency modulation demodulator is connected to the lock-in amplifier.

[0047] The frequency demodulator demodulates the frequency signal modulated by the probe module, removes the high-frequency carrier signal, inputs the demodulated signal into the lock-in amplifier, and uses the frequency of the low-frequency signal applied to the sample under test as the reference frequency for detection, separating and amplifying to generate a high signal-to-noise ratio signal.

[0048] The signal amplifier mentioned is a negative feedback amplifier.

[0049] like Figure 4 As shown, the probe is mounted at the end of a very flexible cantilever beam. When the probe approaches the sample surface, it generates interatomic forces. The movement of the sample in the x and y directions is controlled to achieve scanning. The laser shines on the back of the cantilever beam and is then reflected onto a four-quadrant photodetector to detect the minute bending or deflection of the cantilever.

[0050] A high-frequency small signal is applied to the probe tip, and the sample bottom electrode is grounded; a tiny MOS structure is formed between the probe and the sample; the nonlinear dielectric response of the ferroelectric material causes the capacitance to be slightly modulated with the bias voltage; these signals are extracted by a frequency modulation demodulator and a lock-in amplifier. At each scan point, the output R (amplitude) or θ (phase) of the lock-in amplifier is acquired, and the scan position (x, y) is saved one-to-one with the corresponding signal value; the two-dimensional signal intensity matrix is ​​mapped to a grayscale image or pseudo-color image using software (such as LabVIEW, Gwyddion, Igor Pro, WSxM).

[0051] The measurement steps include: 1. Probe-sample capacitive coupling: A small capacitance C is formed between the probe and the sample surface. s Its value is affected by the sample's dielectric constant, polarization state, and carrier distribution. A low-frequency signal with frequency ω is applied to the sample from its back side. m The system generates high-frequency radio frequency signals (0.5GHz~3.0GHz) through an LC resonant circuit (L is the inductor, C0 is the reference capacitor). When C s When a small shift occurs due to changes in sample properties (such as polarization reversal or carrier migration), the nonlinear dielectric response of the sample causes a frequency shift in the circuit.

[0052] 2. Signal modulation and amplification: The frequency modulation demodulator demodulates the modulated frequency signal, removes the high-frequency carrier signal, and inputs the demodulated signal into the amplifier. The signal frequency applied to the sample is used as the reference frequency for detection, and a high signal-to-noise ratio signal is separated and amplified.

[0053] 3. As Figure 2 , Figure 3 shown, the output signal can be used for the observation of the polarization distribution of strong dielectrics, the ultra-high sensitivity measurement of the charge distribution and impurity distribution in semiconductor devices, and the visualization of the atomic dipole moment using non-contact SNDM (scanning non-linear dielectric microscopy). It adopts the principle of dielectric polarization measurement. The formula for the change of capacitance with an alternating electric field is as follows: ; ΔC - change in alternating capacitance; C s - static capacitance value formed by the probe and the sample; ε - non-linear dielectric constant; E P - applied electric field strength; ω P - angular frequency of the applied low-frequency signal.

[0054] Example: As Figure 5-10 shown is a case of specific measurement, a case of measuring the ferroelectric polarization distribution using the non-linear dielectric constant measurement system based on scanning non-linear dielectric microscopy in the present invention.

[0055] Test material: BTO material (barium titanate).

[0056] 1. Mechanical integration of the probe head and AFM.

[0057] Select a metal tip probe with a ring-shaped ground electrode (225 µm long, 75 kHz, 2.8 N / m).

[0058] Install it on the AFM scanning head and set the force feedback parameters in contact or intermittent contact mode.

[0059] 2. Construction of the LC resonant circuit.

[0060] Connect a variable inductor L in series with a fixed capacitor C0 and tune it to 1 GHz.

[0061] Parallel the probe-sample capacitance C s into the circuit.

[0062] 3. Bias and harmonic excitation.

[0063] Apply a DC bias voltage V_dc (5 V) to determine the operating point.

[0064] Superimpose a small-signal AC bias voltage V_ac (5 mV < VPP < 2 V, 10 kHz) to drive the non-linear response.

[0065] 4. Signal demodulation and acquisition.

[0066] A lock-in amplifier is used to connect to the low-frequency excitation source of the reference, and the output signal is frequency-modulated and demodulated.

[0067] FPGA / MCU samples in real time and outputs frequency offset and phase data.

[0068] 5. Main control software and scanning control.

[0069] Run the scanning path planning module on the PC to generate X–Y–Z control commands.

[0070] PID control is used to adjust the Z-axis force control parameters to ensure constant force sliding of the probe.

[0071] Data buffering and parallel display of the original harmonic amplitude curve.

[0072] 6. Image reconstruction and quantification.

[0073] For 3ω P The signal undergoes bandpass filtering and phase correction to map the ε3 intensity.

[0074] Based on the standard calibration curve, the grayscale values ​​are converted to absolute ε3 units.

[0075] Supports image domain recognition and statistical interfaces.

[0076] 7. Calibration and verification.

[0077] The dC / dV response was calibrated using a linear dielectric standard sample.

[0078] The accuracy of third harmonic imaging was verified using a ferroelectric thin film with a known ε3.

[0079] Regularly check the loop Q value and probe grounding integrity.

[0080] Figure 5 , Figure 6 , Figure 7 , Figure 8 The results were obtained at VPP = 5mV, 10mV, 50mV, and 200mV, respectively. The measured voltage was obtained by processing the original signal frequency through a lock-in amplifier, and the frequency change was obtained by the capacitance formed by the sample. Therefore, its ferroelectricity can be measured. The specific calculation process is as follows: ;in The frequency is GHz. After FM demodulation, the following is obtained: After processing with lock-in detection, the following is obtained: The overall calculation and processing flow is as follows: .

[0081] Figure 9 This is a topographic image; that is, an image obtained from AFM testing, which only shows the surface morphology of the material. Figure 10 A comparison chart of ferropolar polarization distribution measurement results for AFM and SNDM.

[0082] Compared with the prior art, the positive effects of the present invention are: the nonlinear dielectric constant measurement system based on scanning nonlinear dielectric microscopy proposed in this invention breaks through the resolution and sensitivity limits of traditional characterization methods by combining high-frequency nonlinear dielectric response detection with atomic-level probe technology.

[0083] The use of gallium nitride (GaN) probes with diamond coating extends probe life and expands signal processing bandwidth, enabling stronger real-time data acquisition capabilities. The GaN probes have a lifespan of over 1000 hours, which is significantly improved compared to traditional Pt probes (200 hours).

[0084] To address the issue that high-frequency electric fields may cause localized heating of the sample, leading to polarization state drift in ferroelectric materials, this invention employs laser pulses to locally heat the sample, increasing the nonlinear dielectric constant to 1000 times that of room temperature, while simultaneously triggering signal acquisition to avoid the accumulation of thermal disturbances.

[0085] The use of millimeter-wave signal processing enables imaging speeds of up to 3Gbps, which is 30 times faster than traditional SNDM (100Mbps).

[0086] To improve the detection sensitivity of low dielectric constant materials (such as two-dimensional semiconductors), an oxide film is formed on the probe surface, which directly forms a MOS structure with the sample to be tested, resulting in a wider range of measurable materials and greater ease of use.

[0087] Finally, it should be noted that the above descriptions are merely preferred embodiments of the present invention and are not intended to limit the present invention. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments or make equivalent substitutions for some of the technical features. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

[0088] It should be noted that the various embodiments in this specification are described in a progressive manner, with each embodiment focusing on the differences from other embodiments. Similar or identical parts between embodiments can be referred to interchangeably. For the systems or apparatus disclosed in the embodiments, since they correspond to the methods disclosed in the embodiments, the descriptions are relatively simple, and relevant parts can be referred to the method section.

[0089] It should be understood that in this invention, "at least one (item)" refers to one or more, and "more than one" refers to two or more. "And / or" describes the relationship between related objects, indicating that three relationships can exist. For example, "A and / or B" can represent three cases: only A exists, only B exists, and both A and B exist simultaneously, where A and B can be singular or plural. The character " / " generally indicates that the preceding and following related objects are in an "or" relationship. "At least one (item) of the following" or similar expressions refer to any combination of these items, including any combination of single or plural items. For example, at least one (item) of a, b, or c can represent: a, b, c, "a and b", "a and c", "b and c", or "a and b and c", where a, b, and c can be single or multiple.

[0090] It should also be noted that, in this invention, relational terms such as "first" and "second" are used merely to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Without further limitations, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes said element.

[0091] The steps of the methods or algorithms described in conjunction with the embodiments disclosed in this invention can be implemented directly by hardware, a software module executed by a processor, or a combination of both. The software module can be located in random access memory (RAM), main memory, read-only memory (ROM), electrically programmable ROM, electrically erasable programmable ROM, registers, hard disk, removable disk, CD-ROM, or any other form of storage medium known in the art.

[0092] The above description of the disclosed embodiments enables those skilled in the art to make or use the invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined in this invention may be implemented in other embodiments without departing from the spirit or scope of the invention. Therefore, the invention is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A nonlinear dielectric constant measurement system based on a scanning nonlinear dielectric microscope, characterized in that, include: The system comprises a probe, a probe module, a low-frequency signal module, a frequency modulation demodulator, and a lock-in amplifier; a small capacitance C is formed between one end of the probe and the upper surface of the sample to be tested. s The low-frequency signal module applies a low-frequency signal to the lower surface of the sample to be tested; the probe module is composed of an LC resonant circuit and a signal amplifier connected in series, and the other end of the probe is connected to the LC resonant circuit in the probe module. The output of the signal amplifier in the probe module is connected to the frequency modulation demodulator; the output of the frequency modulation demodulator is connected to the lock-in amplifier. The frequency demodulator demodulates the frequency signal modulated by the probe module, removes the high-frequency carrier signal, inputs the demodulated signal into the lock-in amplifier, and uses the frequency of the low-frequency signal applied to the sample under test as the reference frequency for detection, separating and amplifying to generate a high signal-to-noise ratio signal.

2. The nonlinear dielectric constant measurement system based on scanning nonlinear dielectric microscopy as described in claim 1, characterized in that, The probe is a gallium nitride probe.

3. The nonlinear dielectric constant measurement system based on scanning nonlinear dielectric microscopy as described in claim 2, characterized in that, The probe has a diamond coating on its surface.

4. The nonlinear dielectric constant measurement system based on scanning nonlinear dielectric microscopy as described in any one of claims 1-2, characterized in that, The probe has an oxide film on its surface, which can directly form a MOS structure with the sample to be tested.

5. The nonlinear dielectric constant measurement system based on scanning nonlinear dielectric microscopy as described in any one of claims 1-2, characterized in that, The frequency of the high-frequency radio frequency signal generated by the LC resonant circuit is 0.5GHz~3.0GHz.

6. The nonlinear dielectric constant measurement system based on scanning nonlinear dielectric microscopy as described in any one of claims 1-2, characterized in that, The signal amplifier mentioned is a negative feedback amplifier.

7. The nonlinear dielectric constant measurement system based on scanning nonlinear dielectric microscopy as described in any one of claims 1-2, characterized in that, The high signal-to-noise ratio signal is used as the output signal, which can be used to observe the polarization distribution of strong dielectrics, measure the charge distribution and impurity distribution in semiconductor devices with ultra-high sensitivity, and visualize the atomic bipolar torque using a non-contact scanning nonlinear dielectric microscope.

8. The nonlinear dielectric constant measurement system based on scanning nonlinear dielectric microscopy as described in any one of claims 1-2, characterized in that, The probe is installed at the end of the cantilever beam. When the probe approaches the sample surface, it generates interatomic forces, which control the movement of the sample under test in the x and y directions to achieve scanning. The laser shines on the back of the cantilever beam and is then reflected onto the four-quadrant photodetector to detect the minute bending or deflection of the cantilever.

9. The nonlinear dielectric constant measurement system based on scanning nonlinear dielectric microscopy as described in claim 8, characterized in that, A high-frequency small signal is applied to the probe tip, and the sample bottom electrode is grounded; a tiny MOS structure is formed between the probe and the sample; the nonlinear dielectric response of the ferroelectric material causes the capacitance to be slightly modulated with the bias voltage, and the signal generated by the above tiny modulation is extracted by a frequency demodulator and a lock-in amplifier; at each scanning point, the amplitude R or phase θ output by the lock-in amplifier is acquired, and the scanning position is saved one by one with the corresponding signal value; the two-dimensional signal intensity matrix is ​​mapped into a grayscale image or a pseudo-color image using software.

Images