A nano-infrared measurement method and device for polar group orientation and evolution

Abstract

The present invention discloses a nano-infrared measurement method and device for polar group orientation and evolution, the method comprising: using a control circuit to make the probe tip contact with a sample and maintain a stable state; irradiating the sample surface based on an excitation pulse to make the sample and the probe in a tuned resonance state; generating a first voltage signal based on a signal generator and acting on the sample; determining the polar group orientation of the sample based on a second amplitude response signal and the first voltage signal; generating a second voltage signal based on a signal generator and acting on the sample; determining the polar group evolution result of the sample based on a third amplitude response signal and the second voltage signal. The device comprises a signal generation module and a signal processing module. The present invention can be used to perform chemical group orientation and dynamic evolution analysis and measurement of a sample at a nanometer scale. The present invention can be widely used in the fields of nanomechanical measurement and spectral measurement technology.

Description

Technical Field

[0001] The invention relates to the technical field of nano-mechanical measurement and spectral measurement, and in particular to a nano-infrared measurement method and device for polar group orientation and evolution. Background Art

[0002] Atomic force microscopy infrared spectroscopy is a new method developed in recent years to characterize infrared absorption on the surface of materials. It can measure chemical information at the nanoscale by combining atomic force microscopy with infrared spectroscopy. Infrared spectroscopy is a powerful method for analyzing organic substances. Chemical groups with different structures and compositions have different spectral absorption bands. In organic matter, its spectral absorption is richer in the infrared band, and different chemical groups can be distinguished by different infrared absorption peaks. This unique characteristic enables infrared spectroscopy to identify unknown materials and lock a certain group based on chemical specificity. However, traditional infrared spectroscopy is affected by the diffraction limit. Since the wavelength of infrared light is at the micron level, the spatial resolution is also limited to the micron scale. Atomic force microscopy infrared spectroscopy technology realizes nanoscale infrared spectroscopy measurement by combining atomic force probes with infrared spectroscopy.

[0003] The existing atomic force microscope infrared spectroscopy technology characterizes the sample orientation information by relying on the polarization dependence of infrared absorption. Under a linearly polarized light source, the more the transition dipole moment orientation of the chemical group coincides with the orientation of the electric field vector of the linearly polarized light, the stronger the infrared absorption of the chemical group. The existing technology can only distinguish whether the orientation of the chemical group is along the direction of polarized light. For the case where the transition dipole is positively parallel and antiparallel to the direction of the electric field vector of the optical light, the infrared absorption intensity is consistent, and it cannot be distinguished only from the absorption intensity. In addition, in the existing atomic force microscope infrared spectroscopy technology, the information of driving and observing the dynamic evolution of chemical groups cannot be well realized. Due to the lack of external field loading methods and configurations to drive the sample to evolve and synchronously analyze the probe response, for samples that need to observe dynamic evolution, the dynamic evolution of the sample can only be driven by changing the force applied by the probe to the sample. However, the mechanical loading method is not completely applicable. In the standard implementation, the change in the contact force between the probe and the sample itself affects the sensitivity of the probe cantilever beam deflection signal. In addition, the method of inducing evolution through mechanical loading only has a unidirectional force loading, and the tensile force loading cannot be achieved. For some samples, their response to mechanics is not sensitive and cannot induce corresponding evolution. For example, it may be particularly challenging to observe the correlation between the dynamic evolution of ferroelectricity and chemical composition. In such samples, mechanical loading may only induce the dynamic evolution of the sample in one direction, but cannot induce bidirectional dynamic evolution information like electric field.

[0004] Other microscopic characterization techniques based on external field loading can also be used to observe the dynamic evolution of samples, such as piezoelectric force microscopy, Fourier change infrared spectroscopy, and transmission electron microscopy, but these techniques cannot achieve chemical correlation measurements of dynamic evolution of samples at the nanoscale. In standard implementation, piezoelectric force microscopy can characterize the polar orientation of samples and their evolution information under electric fields. Typically, it indicates the orientation information of the polarity of samples by the vibration phase of the probe driven by voltage. However, what is obtained is the macroscopic polar orientation of the sample, and the polar orientation information of specific chemical groups cannot be obtained based on the selection of specific wavelengths, let alone the evolution information of specific chemical polar groups driven by voltage. Fourier change infrared spectroscopy mainly relies on far-field spectral measurement, which cannot provide information on nanoscale samples due to the diffraction limit. Transmission electron microscopy can analyze the chemical composition of samples at the atomic level and infer polar orientation information. However, in standard implementation, its sample preparation process usually includes thinning and destruction of samples, which is less applicable than atomic force microscopy characterization technology.

[0005] In nano-infrared technology, represented by atomic force microscope infrared spectroscopy, it is usually not equipped with external field loading settings, and there is no systematic analysis method for voltage loading under atomic force microscope infrared spectroscopy. In polar characterization, represented by piezoelectric force microscope technology, although it has the ability to measure polar orientation and polarity reversal at the nanoscale, the simple use of voltage makes it impossible to perform infrared characterization of its components while measuring. Therefore, the existing technology has the problem that nano-infrared characterization and polar orientation evolution characterization cannot be achieved at the same time. Summary of the invention

[0006] In order to solve the above technical problems, the object of the present invention is to provide a nano-infrared measurement method and device for polar group orientation and evolution, which can perform chemical group orientation and dynamic evolution analysis and measurement of samples at the nanoscale.

[0007] The first technical solution adopted by the present invention is: a nano-infrared measurement method for polar group orientation and evolution, comprising the following steps:

[0008] Using a control circuit to make the probe tip contact with the sample and maintain a stable state;

[0009] Based on the excitation pulse, the sample surface is irradiated to put the sample and the probe into a tuned resonance state, and a first amplitude response signal is obtained;

[0010] A first voltage signal satisfying the polar group orientation measurement condition is generated based on a signal generator, and a second amplitude response signal is obtained by acting on the sample through the probe and the excitation pulse;

[0011] determining the polar group orientation of the sample based on the second amplitude response signal and the phase direction of the first voltage signal;

[0012] A second voltage signal with a variable amplitude and a specific waveform is generated by a signal generator, and acts on the sample through the probe and the excitation pulse to obtain a third amplitude response signal;

[0013] The polar group evolution result of the sample is determined based on the third amplitude response signal and the second voltage signal.

[0014] Furthermore, the polar group orientation measurement conditions specifically include:

[0015] The frequency of the voltage signal satisfies the conditions for the sample to establish stable polarization and photothermal amplitude;

[0016] The amplitude of the voltage signal is lower than the polarity reversal voltage of the sample.

[0017] Further, the step of determining the polar group orientation of the sample based on the second amplitude response signal and the phase direction of the first voltage signal specifically includes:

[0018] Demodulating the second amplitude response signal based on the first voltage signal to obtain a phase difference value;

[0019] The polar group orientation of the sample is determined based on the phase difference value.

[0020] Further, the step of determining the polar group orientation of the sample based on the phase difference value specifically includes:

[0021] If the phase difference value is 0, the polar groups of the sample are oriented downward;

[0022] If the phase difference value is π, the polar groups of the sample are oriented upward.

[0023] The second technical solution adopted by the present invention is: a nano-infrared measuring device for polar group orientation and evolution, including a signal generating module and a signal processing module, wherein:

[0024] The signal generating module comprises a probe handle end, a probe tip, a sample platform, a probe cantilever beam, a reflected light beam, a deflection detector, an emission source, a scanner, a pulse excitation light source, an excitation light beam, a crystal oscillator, an optical device and a signal generator;

[0025] The signal processing module includes a first processor, a second processor, a first comparison circuit, a second comparison circuit, a first PID gain control circuit and a second PID gain control circuit.

[0026] Furthermore, the first processor and the second processor include a lock-in amplifier and a data acquisition module.

[0027] Furthermore, the first processor is used to filter and demodulate the electrical signal of the deflection detector to obtain the amplitude and phase information of the first output; the second processor is used to filter and demodulate the amplitude information of the first output to obtain the amplitude and phase information of the second output; the first comparison circuit is used to compare the low-frequency probe deflection and the deflection setting value to obtain the first error; the second comparison circuit is used to compare the probe vibration phase and the phase setting value to obtain the second error; the first PID gain control circuit is used to adjust the Z-axis extension and contraction amount of the scanner according to the first error; the second PID gain control circuit is used to adjust the crystal oscillator frequency according to the second error.

[0028] The beneficial effects of the method and device of the present invention are as follows: the present invention uses a signal generator to apply electric field control to the sample while using a pulse excitation light source to apply an infrared excitation signal to the sample, which can induce the sample to evolve, and feed back the evolution results of the polar groups of the sample through the response signal of the probe. The evolution types include ferroelectric polarity evolution, molecular re-orientation arrangement and chemical correlation of evolution; in addition, when a low-amplitude AC voltage is applied to the sample, the infrared absorption evolution of the sample is observed, the orientation of the organic polar groups can be analyzed, and the chemical group orientation and dynamic evolution analysis and measurement of the sample at the nanoscale can be realized. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 It is a schematic flow chart of the steps of a nano-infrared measurement method for polar group orientation and evolution of the present invention;

[0030] Figure 2 is a schematic diagram of a nano-infrared measuring device for polar group orientation and evolution according to the present invention;

[0031] Figure 3 It is a schematic diagram of the principle of judging the change of polar orientation based on the change of amplitude;

[0032] Figure 4 It is an implementation flow chart of a nano-infrared measuring device for polar group orientation and evolution of the present invention;

[0033] Figure 5 It is a curve diagram showing the relationship between the probe amplitude and phase and the demodulator crystal frequency in the tuned resonance state;

[0034] Figure 6 It is a schematic diagram of the change of probe amplitude under the action of AC voltage when the polar group orientation is different;

[0035] Figure 7This is the imaging result diagram of the piezoelectric force microscopy technique characterizing the macroscopic polar direction;

[0036] Figure 8 This is the imaging result diagram of the existing atomic force microscope infrared spectroscopy technology characterizing the direction of polar groups;

[0037] Fig. 9 This is an imaging result diagram of a nano-infrared measurement method for polar group orientation and evolution of the present invention, which characterizes the polar group direction;

[0038] Fig.10 is a graph of the probe amplitude and applied voltage signal versus time;

[0039] Fig.11 is a schematic diagram of the evolution process of the polar groups of polyvinylidene fluoride in a specific embodiment;

[0040] Fig.12 is a voltage modulation signal used in a specific embodiment of the present invention;

[0041] Fig.13 It is a graph of the relationship between infrared absorption and voltage under different wavelengths;

[0042] Description of the drawings: 1. Probe handle end; 2. Probe tip; 3. Sample platform; 4. Probe cantilever beam; 5. Reflected light beam; 6. Deflection detector; 7. Emission source; 8. Scanner; 9. Pulse excitation light source; 10. Excitation light beam; 11. Crystal oscillator; 12. Second PID gain control circuit; 13. Optical device; 14. Signal generator; 15. First processor; 16. First comparison circuit; 17. Second comparison circuit; 18. Second processor; 19. First PID gain control circuit. DETAILED DESCRIPTION

[0043] The present invention is further described in detail below in conjunction with the accompanying drawings and specific embodiments. The step numbers in the following embodiments are only provided for the convenience of explanation and description, and the order between the steps is not limited in any way. The execution order of each step in the embodiment can be adaptively adjusted according to the understanding of those skilled in the art.

[0044] The feature of the present invention is that the measured results have available chemical specificity by loading infrared pulses and voltage excitation at the same time. In traditional piezoelectric force microscopes, polarity measurement is usually carried out by voltage loading, but the results do not have the specificity of infrared absorption. Simply measuring the piezoelectric force microscope signal under infrared pulse excitation cannot obtain specific polarity orientation and evolution information through the inverse piezoelectric effect. The testing principle of the piezoelectric force microscope is to use alternating current to excite the sample to produce the inverse piezoelectric effect. The inverse piezoelectric effect causes the probe to vibrate, and the amplitude and phase of the probe reflect the polarity strength and direction. After simply superimposing the infrared pulse excitation, the phase of the probe will be disturbed, and the direction of the polarity cannot be directly analyzed.

[0045] Reference Figure 1 , a nano-infrared measurement method for polar group orientation and evolution, comprising the following steps:

[0046] S1. Use the control circuit to make the probe tip contact with the sample and maintain a stable state;

[0047] Specifically, since the probe cantilever beam actually used in the specific embodiment of the present invention is usually a few microns to tens of microns in length, and the tip radius is usually tens of nanometers, in order to achieve the stability of the contact state between the probe and the sample and maintain a stable contact force, the processor circuit needs to perform fine-grained regulation and processing of the contact situation.

[0048] S2, irradiating the sample surface based on the excitation pulse, so that the sample and the probe are in a tuned resonance state, and obtaining a first amplitude response signal;

[0049] Specifically, the excitation pulse light source includes but is not limited to visible light, infrared light and terahertz light sources. The specific embodiment of the present invention uses an infrared excitation pulse to irradiate the sample surface. After the sample absorbs the infrared excitation pulse, local thermal expansion occurs. The thermal expansion causes the probe in contact with it to deflect and oscillate. When the frequency of the infrared excitation pulse matches the contact resonance frequency of the sample, the sample and the probe are in a tuned resonance state, and the deflection vibration of the probe is obtained as a first amplitude response signal. The first amplitude response signal can be demodulated by the excitation pulse signal to reflect the infrared absorption intensity of the sample.

[0050] Reference Figure 3 In a specific embodiment of the present invention, a light beam with a vertical linear polarization direction is used to reflect the rotation information of a specific chemical group of the sample. Due to the polarization-dependent characteristics of infrared absorption, the infrared absorption intensity of the sample depends on the relationship between the transition dipole moment direction and the polarization direction of the target group. When the angle between the transition dipole moment direction and the polarization direction of the light beam is smaller, the more the two overlap, and the stronger the infrared absorption response. When the angle between the transition dipole moment direction and the polarization direction of the light beam is larger, the infrared absorption response is smaller.

[0051] Reference Figure 5 , the crystal oscillator sends out a TTL level pulse trigger signal through the circuit every time it oscillates one cycle, and the level pulse trigger signal triggers the pulse laser to emit an infrared excitation pulse. The duty ratio of the infrared excitation pulse is set to 10% or 100ns. There is no fixed requirement for the pulse time, and it can be adjusted to the state with the best signal-to-noise ratio according to the test sample and conditions. Because the infrared pulse excites the sample to produce thermal expansion deformation of the same frequency, the impact probe produces deflection vibration of the same frequency. Using the AC signal generated by the crystal oscillator as a reference signal, the amplitude of the probe deflection can be demodulated by the first processor. As the frequency of the crystal oscillator changes, the probe amplitude will be amplified. The frequency of this amplification enhancement is usually the contact resonance frequency between the probe and the sample, that is, f1.

[0052] After the contact resonance frequency f1 is determined, the phase-locked loop is used to keep the probe vibrating at the contact resonance frequency during the test. Specifically, the vibration phase of the probe obtained by demodulation by the first processor is input as an input signal to the second comparison circuit and compared with the phase reference value. The second error obtained by the comparison is used as a parameter and input into the second PID gain control circuit to adjust the increase or decrease of the laser pulse frequency.

[0053] S3, generating a first voltage signal satisfying the polar group orientation measurement condition based on a signal generator, and obtaining a second amplitude response signal by acting on the sample through the probe and the excitation pulse;

[0054] Specifically, the polar group orientation measurement conditions include:

[0055] The frequency of the voltage signal satisfies the conditions for the sample to establish stable polarization and photothermal amplitude;

[0056] The amplitude of the voltage signal is lower than the polarity reversal voltage of the sample.

[0057] When the first voltage signal that meets the polar group orientation measurement condition acts on the sample in a coordinated resonance state through the probe, the deflection vibration of the probe changes, and a second amplitude response signal is obtained.

[0058] S4, determining the polar group orientation of the sample based on the second amplitude response signal and the phase direction of the first voltage signal;

[0059] S4.1. Demodulate the second amplitude response signal based on the first voltage signal to obtain a phase difference value;

[0060] S4.2. Determine the polar group orientation of the sample based on the phase difference value.

[0061] Specifically, refer to Figure 6, the voltage is set to sinusoidal alternating current. The frequency is much lower than the frequency of the probe contact resonance. Because under sinusoidal alternating current, the polarity of the group will swing slightly with the voltage amplitude. The purpose of low voltage change frequency is to make the swing of the group polarity smooth so as to leave enough demodulation time to demodulate the probe amplitude. The voltage uses a small amplitude voltage to only disturb the polarity direction of the sample without inducing it to flip. Under vertically polarized light, when the polar group of the sample is oriented upward, the phase difference between the first voltage signal and the second amplitude response signal is π; when the polar group of the sample is oriented downward, the phase difference between the first voltage signal and the second amplitude response signal is 0.

[0062] According to the phase direction of the first voltage signal and the second amplitude response signal, the polar group orientation of the sample can be reflected, and the technical principle is as follows:

[0063] Under vertical polarized light, when the polar group of the sample is oriented upward, if the first voltage signal input is a positive voltage, the polarity direction will be deflected downward, deviating from the vertical polarization direction, and the probe amplitude will be reduced; if the first voltage signal input is a negative voltage, the polarity direction will be deflected upward, more closely aligned with the vertical polarization direction, and the probe amplitude will be increased. Therefore, the demodulation phase value of the first voltage signal and the second amplitude response signal is π.

[0064] Under vertical polarized light, when the polar group of the sample is oriented downward, if the first voltage signal input is a positive voltage, the polarity direction will be deflected downward, more closely aligned with the vertical polarization direction, and the probe amplitude will increase; if the first voltage signal input is a negative voltage, the polarity direction will be deflected upward, deviating from the vertical polarization direction, and the probe amplitude will decrease. Therefore, the demodulation phase value of the first voltage signal and the second amplitude response signal is 0.

[0065] Typically, the second amplitude response signal of the probe is modulated by the first voltage signal. The second amplitude response signal of the probe can be used as a second processor input signal, and the amplitude is demodulated with the first voltage signal of the AC frequency f2 applied as a reference signal to obtain phase information of the second amplitude response signal relative to the first voltage signal, and the phase information reflects the orientation of the polar group.

[0066] The sample used in the specific embodiment of the present invention is a typical ferroelectric polymer P (VDF-TrFE) thin film with a thickness of about 100 nm. The sample was previously mapped with a special pattern of polar domain structure using piezoelectric force microscopy technology. Figure 7 Phase and amplitude images of the piezoelectric force microscope in Figure 1. It shows that the sample was written with a nested "U"-shaped polar domain structure with opposite polarity orientation by a voltage of 25V positive and 25V negative. The comparative example was set up with a 1289cm -1The band used existing atomic force microscopy infrared spectroscopy technology to image and map the area, referring to Figure 8 It can be found that due to the difference in electronegativity between CF and CH, the directions of the positive and negative polarity domain structures are basically consistent in amplitude intensity in the existing atomic force microscope infrared spectroscopy technology, and it is impossible to distinguish the difference in polarity direction between the positive and negative polarity domain structures. -1 The band was used to draw the phase imaging of the region by the method of the present invention, referring to Fig. 9 It can be found that after loading with alternating current and performing the above-mentioned phase analysis on the change of the probe amplitude under the action of alternating current, the phase obtained has the same nested polarity domain structure, and the polarity domain structures in different directions have a phase difference of about 180 degrees in imaging, which can distinguish the positive and negative directions of the polarity.

[0067] S5, generating a second voltage signal of a variable amplitude with a specific waveform based on a signal generator, and acting on the sample through the probe and the excitation pulse to obtain a third amplitude response signal;

[0068] Specifically, the specific waveform includes but is not limited to a triangular wave and a square wave pulse modulated by a triangular wave. The second voltage signal is transmitted to the probe tip through the conductive coating on the probe in contact with the sample and acts on the sample. After being modulated by the second voltage signal, the polarity orientation in the organic sample is changed by the voltage and evolves with the driving of the second voltage signal, and the deflection vibration of the probe changes, thereby obtaining a third amplitude response signal.

[0069] S6. Determine the polar group evolution result of the sample based on the third amplitude response signal and the second voltage signal.

[0070] Specifically, the third amplitude response signal of the probe under the second voltage signal of different amplitudes can reflect how the polar group evolves under the action of voltage. If the probe amplitude response becomes smaller, it means that the orientation of the polar group deviates from the polarization direction of the light. Otherwise, it means that it is approaching the polarization direction of the light.

[0071] Reference Fig.10 , the specific embodiment of the present invention adopts a DC square wave in the form of a triangular wave with a large amplitude. Under the induction of a DC voltage of sufficient intensity, the sample undergoes ferroelectric reversal evolution of polarity. The initial sample is polarized by a 30V voltage. As the electric field decreases and increases negatively to reach a negative coercive voltage, the polarity begins to reverse and experiences an intermediate state in which the polarity is almost perpendicular to the polarization direction of the light. At this time, the probe amplitude decreases and reaches a minimum value. Subsequently, the polarity continues to reverse and reaches a reverse vertical orientation. At this time, the probe amplitude gradually resumes growth. And then, as the negative voltage decreases, the positive voltage increases and reaches a positive coercive field, the polarity undergoes reversal again, and the amplitude undergoes a process of decreasing and then increasing again.

[0072] The specific embodiment of the present invention uses a ferroelectric polymer film P (VDF-TrFE) as a sample and adopts a 1289 cm -1 band, can reflect CF 2 Symmetric stretching vibration mode v s (CF 2 ), the direction of its transition dipole moment is referenced to Fig.11 ; Using 1183cm -1 band, can reflect CF 2 Antisymmetric stretching vibration mode v as (CF 2 ), whose transition dipole moment direction is similar to that of 1289cm -1 The transition dipole moments of the bands are perpendicular to each other. In the process of voltage-induced macroscopic polar rotation, 1289cm -1 During the evolution process, the angle between the transition dipole moment direction of the band and the polarization direction of the beam line will go through a process of increasing and then decreasing. Due to the polarization dependence of infrared absorption, the infrared response will go through a process of decreasing and then increasing.

[0073] The specific embodiment of the present invention further studies the influence of voltage modulation on infrared absorption response at a fixed wavelength. The voltage modulation signal used can refer to Fig.12 ,exist Fig.12 The curve of the relationship between infrared absorption and voltage under the voltage modulation signal is shown in the figure below. Fig.13 It can be found that under voltage modulation, 1289cm -1 The change of infrared absorption (amplitude) in the band shows a special butterfly pattern evolution. The dots are the sampling points of the experimental results, and the solid line is the fitting curve. In the voltage cycle from positive 35V to negative 35V, the polarity experienced two ferroelectric reversals from up to down and from down to up. The reversal of macroscopic polarity comes from the rotational evolution of the polarity of microscopic functional groups. -1 The butterfly pattern of the band reflects the CF 2 The group undergoes a flip of the transition dipole moment at around 20 V. Since the flip has ferroelectric hysteresis characteristics, it presents a butterfly pattern. -1 The transition dipole moment direction of the band is similar to that of 1289cm -1 Perpendicular to each other, when one direction is close to parallel to the polarization direction of light and reaches a maximum value, the other direction is close to perpendicular and reaches a minimum value. -1 The band also shows a butterfly pattern evolution, and compared with 1289cm -1 The patterns of the bands are inverted; the infrared loops of both reflect Fig.11 The polarity evolution process in .

[0074] Reference Figure 2, a nano-infrared measuring device for polar group orientation and evolution, comprising a signal generating module and a signal processing module, wherein:

[0075] The signal generating module comprises a probe handle end 1, a probe tip 2, a sample platform 3, a probe cantilever beam 4, a reflected light beam 5, a deflection detector 6, an emission source 7, a scanner 8, a pulse excitation light source 9, an excitation light beam 10, a crystal oscillator 11, an optical device 13 and a signal generator 14;

[0076] The signal processing module includes a first processor 15 , a second processor 18 , a first comparison circuit 16 , a second comparison circuit 17 , a first PID gain control circuit 19 and a second PID gain control circuit 12 .

[0077] The reflected light beam 5 and the deflection detector 6 use an optical lever to realize probe deflection detection. The reflected light beam 5 is guided to the probe cantilever beam 4 via the emission source 7 and reflected to the deflection detector 6. The deflection detector 6 detects the strength of the light beam signal in each quadrant to determine the deflection information of the probe.

[0078] The scanner 8 is used to generate the mutual movement between the sample and the probe, so that the probe tip 2 scans the sample surface to obtain various characteristics of the sample surface. The scanner 8 includes an xyz three-axis displacement device such as a piezoelectric ceramic tube. Alternatively, the scanner can also be a plurality of separate displacement devices, such as an independent xy displacement device to move the sample, and in this way and an independent z-axis displacement device to control the interaction between the probe and the sample. By maintaining the probe deflection degree at a set value, the interaction between the probe and the sample during the relative movement can be maintained constant. Usually, the adjustment displacement in the z-axis direction is recorded as a measured value of the height of the sample surface.

[0079] The pulse excitation light source 9 emits an excitation light beam 10 which is focused through an optical device 13 to an interaction area between the probe tip 2 and the test sample on the sample platform 3 ; the excitation light beam 10 is obtained by frequency modulation of a crystal oscillator 11 .

[0080] The first processor 15 includes a phase-locked amplifier and a data acquisition module. The data acquisition module can collect the probe deflection vibration information reflected by the deflection detector 6. The deflection vibration information is demodulated by the phase-locked amplifier to obtain an amplitude signal.

[0081] The signal generator 14 is used to generate a voltage signal with a variable waveform and amplitude, which is applied to the test sample on the sample platform 3 below the probe tip through the probe cantilever 4 and the conductive metal coating attached to the probe tip 2. The voltage signal will induce the sample to undergo a dynamic evolution of polarity, including but not limited to polarity rotation, chemical structure deformation, chemical composition redistribution, etc. The light beam pulse and the voltage signal are applied simultaneously during the measurement process.

[0082] The first processor 15 is used to filter and demodulate the electrical signal of the deflection detector 6 to obtain the amplitude and phase information of the first output; the second processor 18 is used to filter and demodulate the amplitude information of the first output to obtain the amplitude and phase information of the second output; the first comparison circuit 16 is used to compare the low-frequency probe deflection and the deflection setting value to obtain the first error; the second comparison circuit 17 is used to compare the probe vibration phase and the phase setting value to obtain the second error; the first PID gain control circuit 19 is used to adjust the Z-axis extension and contraction amount of the scanner according to the first error; the second PID gain control circuit 12 is used to adjust the crystal oscillator frequency according to the second error.

[0083] Reference Figure 4 , the operation process of the device is as follows:

[0084] Step 1: The probe tip 2 is brought into surface contact with the test sample on the sample platform 3. The contact force is controlled by the scanner 8 and the feedback system and maintained at a set value.

[0085] Step 2: Tune the light source to the target wavelength to be tested.

[0086] Step 3: Tune the pulse frequency of the light source to the contact resonance frequency.

[0087] Specifically, after determining the contact resonance frequency, the probe vibration phase is obtained by demodulating the phase-locked amplifier in the first processor 15, and the probe vibration phase is input as an input signal into the second comparison circuit 17 for comparison with the reference value; the second error obtained by comparison is further used as a parameter and input into the second PID gain control circuit to adjust the increase or decrease of the laser pulse frequency.

[0088] Step 4: Use the excitation light source 9 to emit an excitation light beam 10 to illuminate the sample area near the probe tip through the optical device 13.

[0089] Step 5: The voltage signal is tuned to the target intensity to be tested and the target test waveform through the signal generator 14 .

[0090] Step 6: The voltage signal is transmitted to the probe with conductive coating through the transmission line conductor and acts on the sample under the probe tip.

[0091] Step 7: The deflection detector 6 detects the oscillation signal of the probe and transmits the detection signal to the first processor 15 and the second processor 18 for demodulation processing.

[0092] Step 8: The measurement parameters including the infrared wave number, voltage magnitude, and the amplitude and phase of the probe oscillation signal are collected and recorded.

[0093] Step 9: Repeat the measurement at different wavelengths to achieve the measurement of different characteristic chemical substances during the voltage-induced evolution process, and return to step 7 after repeating.

[0094] Step 10: Repeat the measurement at different voltages to achieve the measurement of different polarity evolution states during the voltage-induced evolution process, and return to step 6 after repetition.

[0095] Step 11: Repeat the measurement at different locations and return to step 7 if repeated.

[0096] Step 12: Generate a voltage evolution component map or a polar orientation map.

[0097] The contents of the above-mentioned device embodiments are all applicable to the present method embodiments. The functions specifically implemented by the present method embodiments are the same as those of the above-mentioned device embodiments, and the beneficial effects achieved are also the same as those achieved by the above-mentioned method embodiments.

[0098] The above is a specific description of the preferred implementation of the present invention, but the invention is not limited to the embodiments. Those skilled in the art may make various equivalent modifications or substitutions without violating the spirit of the present invention. These equivalent modifications or substitutions are all included in the scope defined by the claims of this application.

Claims

1. A nano-infrared measurement method for polar group orientation and evolution, characterized in that: The following steps are involved: Using a control circuit to make the probe tip contact with the sample and maintain a stable state; Based on the excitation pulse, the sample surface is irradiated to put the sample and the probe into a tuned resonance state, and a first amplitude response signal is obtained; A first voltage signal satisfying the polar group orientation measurement condition is generated based on a signal generator, and a second amplitude response signal is obtained by acting on the sample through the probe and the excitation pulse; determining the polar group orientation of the sample based on the second amplitude response signal and the phase direction of the first voltage signal; A second voltage signal with a variable amplitude and a specific waveform is generated by a signal generator, and acts on the sample through the probe and the excitation pulse to obtain a third amplitude response signal; The polar group evolution result of the sample is determined based on the third amplitude response signal and the second voltage signal.

2. A nano-infrared measurement method for polar group orientation and evolution according to claim 1, characterized in that: The polar group orientation measurement conditions specifically include: The frequency of the voltage signal satisfies the conditions for the sample to establish stable polarization and photothermal amplitude; The amplitude of the voltage signal is lower than the polarity reversal voltage of the sample.

3. A nano-infrared measurement method for polar group orientation and evolution according to claim 1, characterized in that: The step of determining the polar group orientation of the sample based on the second amplitude response signal and the phase direction of the first voltage signal specifically includes: Demodulating the second amplitude response signal based on the first voltage signal to obtain a phase difference value; The polar group orientation of the sample is determined based on the phase difference value.

4. A nano-infrared measurement method for polar group orientation and evolution according to claim 3, characterized in that: The step of determining the polar group orientation of the sample based on the phase difference value specifically includes: If the phase difference value is 0, the polar groups of the sample are oriented downward; If the phase difference value is π, the polar groups of the sample are oriented upward.

5. A nano-infrared measuring device for polar group orientation and evolution, applied to a nano-infrared measuring method for polar group orientation and evolution as claimed in any one of claims 1 to 4, characterized in that: It includes a signal generation module and a signal processing module, wherein: The signal generating module comprises a probe handle end, a probe tip, a sample platform, a probe cantilever beam, a reflected light beam, a deflection detector, an emission source, a scanner, a pulse excitation light source, an excitation light beam, a crystal oscillator, an optical device and a signal generator; The signal processing module includes a first processor, a second processor, a first comparison circuit, a second comparison circuit, a first PID gain control circuit and a second PID gain control circuit.

6. A nano-infrared measuring device for polar group orientation and evolution according to claim 5, characterized in that: The first processor and the second processor include a lock-in amplifier and a data acquisition module.

7. A nano-infrared measuring device for polar group orientation and evolution according to claim 5, characterized in that: The first processor is used to filter and demodulate the electrical signal of the deflection detector to obtain the amplitude and phase information of the first output; the second processor is used to filter and demodulate the amplitude information of the first output to obtain the amplitude and phase information of the second output; the first comparison circuit is used to compare the low-frequency probe deflection and the deflection setting value to obtain the first error; the second comparison circuit is used to compare the probe vibration phase and the phase setting value to obtain the second error; the first PID gain control circuit is used to adjust the Z-axis extension and contraction amount of the scanner according to the first error; the second PID gain control circuit is used to adjust the crystal oscillator frequency according to the second error.

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