Resonance enhancement detection method using scanning probe microscopy and modulation frequency range

Abstract

Scanning probe microscopy and resonance enhancement detection methods using scanning probe microscopy employ a light source modulated within a frequency range to illuminate the interface between the microscope's probe tip and the sample, which receives electromagnetic radiation modulated by the self-source light source. Then, at the probe tip-sample interface, in response to the modulated electromagnetic radiation, the vibrational response of the driven cantilever is measured. The amplitude of the cantilever's vibrational response is measured across the entire modulation frequency range to derive photo-induced force microscopy (PiFM) values.

Description

Technical Field

[0001] This application may benefit from U.S. Provisional Patent Application No. 62 / 949,404, filed on December 17, 2019, which is incorporated herein by reference. Background Technology

[0002] In scanning probe microscopy (SPM), the resonance of the cantilever probe is often preferred to amplify the signal from the force being measured. This typically involves providing a tip-sample force interaction modulated at the resonant frequency, which increases energy over several cycles to produce a larger deflection than could be achieved with the same force modulation at a non-resonant frequency. However, the probe's resonant frequency and Q can shift as the probe interacts with the sample. In particular, the resonant frequency can shift due to different local material properties of the sample surface and imperfect maintenance of the tip-sample distance. When using specialized versions of SPM (e.g., photo-induced force microscopy, PiFM), light absorption due to localized regions of the sample also affects the tip-sample force interaction, thus shifting the resonant frequency and Q. When using a static excitation frequency, this fixed frequency deviates from the peak frequency, resulting in a non-constant amplification factor in the cantilever's response. These varying amplification factors mean that measurement sensitivity can differ depending on time, position on the sample surface, or the wavelength and intensity of light applied to the interface. The resulting variation in response due to this resonance can introduce errors into the reported data, which are not easily corrected in the acquired data. Summary of the Invention

[0003] Scanning probe microscopy and resonance-enhanced detection methods using scanning probe microscopy employ a light source modulated within a frequency range to illuminate the interface between the microscope probe tip and the sample, which emits electromagnetic radiation modulated by the self-source light source. Then, at the probe tip-sample interface, in response to the modulated electromagnetic radiation, the vibrational response of the driven cantilever is measured. The amplitude of the cantilever's vibrational response is measured across the entire modulation frequency range to derive photo-induced force microscopy (PiFM) values.

[0004] A resonance enhancement detection method using a scanning probe microscope according to an embodiment of the present invention includes the steps of: driving a cantilever to vibrate with the probe tip of the scanning probe microscope; modulating a light source within a frequency range to illuminate the interface between the probe tip and a sample having electromagnetic radiation modulated by the light source; detecting the vibration response of the cantilever at the interface between the probe tip and the sample in response to the modulated electromagnetic radiation; and measuring the amplitude of the vibration response of the cantilever over the entire modulation frequency range to derive a photo-induced force microscope (PiFM) value.

[0005] A scanning probe microscope according to an embodiment of the present invention includes: a cantilever having a probe tip; a dither drive unit coupled to the cantilever to drive the cantilever to vibrate; a light source illuminating the interface between the probe tip and the sample; a signal generator coupled to the light source modulating the light source within a frequency range to illuminate the interface between the probe tip and the sample having electromagnetic radiation modulated by the light source; a detector detecting the vibration response of the cantilever at the interface between the probe tip and the sample in response to the modulated electromagnetic radiation; and an amplitude measurement system measuring the amplitude of the vibration response of the cantilever over the entire modulation frequency range to derive photo-induced force microscope (PiFM) values.

[0006] Other aspects and advantages of the invention will become clearer from the following detailed description, which is illustrated in conjunction with the accompanying drawings, which serve as examples of the principles of the invention. Attached Figure Description

[0007] Figure 1 Examples of three resonance curves obtained from different locations on a non-homogeneous sample are shown.

[0008] Figure 2 A scanning probe microscope according to an embodiment of the present invention is shown.

[0009] Figure 3 A scanning probe microscope according to an alternative embodiment of the invention is shown.

[0010] Figure 4 A scanning probe microscope according to another embodiment of the present invention is shown.

[0011] Figure 5 This is a flowchart of a resonance enhancement detection method using a modulation frequency range according to an embodiment of the present invention. Detailed Implementation

[0012] The need to monitor and correct resonance variations in a cantilever motor resonance (SPM) has been recognized in the past, and various types of solutions have been reported in existing literature and patents. One type of solution involves periodically or continuously measuring the frequency response of the cantilever resonant frequency or the phase of the cantilever oscillation and adjusting the appropriate modulation frequency in the SPM to track the changing resonant frequency. Another solution is to apply a frequency range covering (by sweeping or band excitation) the expected variation of the resonant frequency and measure the response as a function of the modulation frequency to determine the peak frequency and report the signal amplitude at the peak. The main drawback of both methods is that the frequency response of a particular cantilever resonant often exhibits a degree of complexity that makes identifying individual peak frequencies difficult or impossible. Resonant frequency response curves can have a variety of characteristics, ranging from an ideal Lorentzian-shaped single peak with a clearly defined Q to complex response curves with multiple maximum and minimum values, and even an overall shape far removed from the ideal Lorentzian shape. In such cases, the problem arises in determining the "peak frequency" to track or report the response.

[0013] Figure 1 Example three resonance curves obtained from different locations on a non-homogeneous sample are shown. As can be seen from these three curves, the peak frequency of the resonance and the overall structure of the curves both vary between the three locations. Of the three curves, curve C is closest to the expected peak shape, while curve B is particularly problematic because it has multiple maximum values ​​that can lead to errors when identifying a specific resonance peak. The phase of the vibration is not shown. Figure 1 However, it is also complex, making it impossible for the phase-locked loop to automatically select and fix a precise resonant peak.

[0014] Existing peak tracking methods include those described below: (1) R.Arinero el al, "Imageprocessing for resonance frequency mapping in atomic force modulationmicroscopy," Rev.Sci.Instrum.78,023703(2007), (2)G.Ramer et al, "Implementation of Resonance Tracking for Assuring Reliability in Resonance EnhancedPhotothermal Infrared Spectroscopy and Imaging,"Appl.Spectrosc.71,2013-2020(2017),(3)C.Prater and K.Kjoller,USPatent Number8,680,467,"High frequencydeflection measurement of IR absorption with a modulated IR source,"filed 9 / 19 / 11,issued 3 / 25 / 14,and (4)Prater and K.Kjoller,USPatent Number 10,228,388,“Method and apparatus for resolution "and sensitivity-enhanced atomic force microscope based on infrared spectroscopy," filed 11 / 10 / 16, issued 3 / 12 / 19. This reference focuses on finding and reporting the peak frequencies of resonance curves, as well as reporting the response amplitude at those peak frequencies.

[0015] Another existing approach includes the band excitation method described in S. Jesse et al., “The band excitation method inscanning probe microscopy for rapid mapping of energy dissipation on nanoscale,” Nanotechnology 18 435503 (2007). This reference shares essentially the same focus on finding the peak frequency and the response within that frequency range; the band excitation method simply applies a frequency range simultaneously and measures the response as a function of frequencies within that range. While the band excitation method offers certain advantages over peak tracking methods that scan or track frequencies, its output is not integrated over the range of interest, thus exhibiting the same drawbacks as peak tracking methods when the resonant frequency response becomes complex to operate on.

[0016] Embodiments of the present invention address this drawback by solving the problem in a different way. Instead of tracking changing resonant frequencies or searching for a suitable frequency range for the purpose of finding a response at a single "peak" frequency, the response is integrated and reported over the frequency range. This has the effect of summing the responses over all frequencies within the range of interest, which is not particularly advantageous when the frequency response curve runs well at a single Lorentz peak. The frequency range can be achieved by scanning a single frequency within the target range or by simultaneously applying a band excitation of the frequency components. When using a scanned frequency, typical lock-in signal detection can be used with an integrator at the output. For band excitation, a single amplitude envelope measurement can be implemented.

[0017] Then, refer to Figure 2 The illustration shows a photoluminescence microscopy (PiFM) apparatus 200 as an embodiment of a scanning probe microscope according to the present invention. The PiFM apparatus 200 includes: a probe tip 202 coupled to a cantilever 204; a light source 206 modulated into a tunable laser 206 for illuminating the interface between the probe tip and the sample 208 with electromagnetic radiation; a jitter control system 210 for setting a fixed distance between the probe tip and the sample; and a laser modulation control system 212 for modulating the tunable laser within a modulation frequency range to output an amplitude value integrated over the entire modulation frequency range as PiFM data usable for imaging the sample. In one embodiment, the modulated tunable laser 206 is an infrared (IR) laser.

[0018] The jitter control system 210 of the PiFM device 200 includes a jitter drive unit 214, a jitter piezoelectric device 216 coupled to the cantilever 204, a position feedback laser 218, an optical position detector 219, a first lock detector or amplifier 220, a sample Z servo controller 222, and a sample Z piezoelectric device 224. For an example of amplitude modulation (AM) detection (also known as “gradient detection”), the jitter drive unit 214 is configured to provide a signal with a desired drive frequency to the jitter piezoelectric device 216, causing the cantilever 204 to vibrate. The optical position detector 219 uses light from the position feedback laser 218 reflected from the cantilever to optically measure the vibration of the cantilever 204. The signal from the optical position detector 219 is input to the first lock detector 220, which provides an amplitude error signal to the sample Z servo controller 222. The amplitude error signal indicates that the distance between the tip 202 and the sample 208 deviates from the desired distance. In response, the sample Z servo controller 222 provides a control signal to the sample Z piezoelectric device 224 to adjust the distance between the tip 202 and the sample 208. Specifically, the jitter frequency is fixed at a slightly higher position than the resonant frequency of the jitter vibration mode of the cantilever 204. When the tip-sample distance decreases below the target value, the jitter mode frequency shifts downward, effectively moving the jitter drive frequency above resonance to reduce the jitter amplitude (and vice versa). The sample Z servo controller 222 applies a correction to the voltage on the sample Z piezoelectric device 224 to determine the amplitude error and return the tip-sample distance to the target value. As the sample 208 is raster-scanned relative to the tip 202, topography data is acquired in the output of the sample Z servo controller 222, and mechanical phase data (related to the sample's mechanical stiffness and damping) is provided in the phase output of the lock detector 220.

[0019] The jitter control system 210 can be replaced by frequency modulation (FM) detection without affecting the rest of the PiFM device 200. When operating with a very high cantilever Q, FM may be preferred in AM mode because the control loop response speed and imaging speed may be too slow.

[0020] The laser modulation control system 212 of the PiFM device 200 includes a scan frequency generator 226, an electronic mixer 228, a second lock detector or amplifier 230, and an integrator 232. The scan frequency generator 226 generates a modulation drive signal for the tunable laser 206 within a scan modulation frequency range that includes the resonant frequency. The scan frequency range can be +5% or -5% or more of the resonant frequency of the cantilever 204. As an example, in... Figure 1In this configuration, when the resonant frequency is 247 kHz, the scan frequency range can be 230 kHz to 260 kHz, corresponding to +6% / -6% (or a 12% range). Electronic mixer 228 is used to mix the jitter drive signal from the first frequency of jitter drive device 214 and the modulation drive signal from the second frequency of scan frequency generator 226 to generate an output signal in the sum frequency that matches the cantilever resonant frequency. Second lock detector 230 uses the sum frequency signal from mixer 228 as a reference to the cantilever vibration response signal from optical position detector 219 to generate an output representing the amplitude of the cantilever vibration relative to the current modulation frequency. As the modulation frequency suitable for tunable laser 206 is scanned through the modulation frequency range, integrator 232 operates to integrate the output of second lock detector 230. The output of integrator 232 is PiFM data for each position measured on the sample, which can be used to image sample 208. Since the mixer 228, the second lock detector 230, and the integrator 232 are used to measure the integral amplitude value, this component can be considered as part of the amplitude measurement system.

[0021] In one embodiment, a tunable infrared (IR) laser 206 of a pulsed or amplitude-modulated PiFM device 200 radiates light onto the interface between the probe tip 202 and the sample 208. In this embodiment, the PiFM device 200 operates in sideband mode, and the laser modulation frequency is the difference frequency between the dithering drive frequency and the resonant frequency of the vibrational mode used for PiFM detection. Instead of a fixed-frequency signal generator, the PiFM device 200 in this embodiment uses a scanning frequency generator 226 that scans a sufficiently wide frequency range to cover the expected shift of the cantilever resonant frequency during the experiment. The nonlinear interaction between the illuminated tip 202 and the sample 208 results in a frequency mixing of the dithering frequency and the laser modulation frequency, producing a sum frequency that matches the cantilever resonant. This identical frequency is generated by an electronic mixer 228 using signals from the dithering drive unit 214 and the scanning frequency generator 226. In the sum-frequency analysis, a cantilever deflection signal from optical position detector 219, including a PiFM component, is applied to the input of a second lock detector 230, whose reference signal is a sum-frequency signal electronically generated by mixer 228. During each frequency scan performed by scan frequency generator 226, the amplitude output of the second lock detector 230 is configured to be integrated to provide an integrated single photomicroscopy (PiFM) value at the end of each scan as a single photomicroscopy (PiFM) data point that can be used for PiFM imaging. In one embodiment, scan frequency generator 226 may be configured to generate an optional trigger output after each frequency scan, which can be used to clear integrator 232 before each frequency scan begins.

[0022] In some embodiments, various experimental factors can be selected to optimize the measured PiFM data. For example, tip-sample position, time, wavelength of applied light, tip-sample distance, sample temperature, intensity of applied light, and / or tip and its coating type can be selected to derive optimized PiFM data. Additionally, in some embodiments, an alternative to using sum frequencies is to use difference frequencies generated by mixer 228. Similarly, in some embodiments, an alternative to using difference frequencies is to use sum frequencies.

[0023] It is important to note that the time constant of the output of the second lock detector 230 should be significantly shorter than the sweep repetition rate, unless the output time constant is intended to be used as an integration mechanism (typically 5X-50X shorter). Furthermore, at PiFM signal frequencies, the sweep repetition rate should be significantly slower than the time constant of the amplitude variation of the cantilever 204, determined by the frequency and Q of the cantilever oscillation (typically 5X-50X shorter). This factor limits the speed of PiFM data acquisition.

[0024] Next, refer to Figure 3 The illustration shows a PiFM device 300 according to an alternative embodiment of the invention. In this embodiment, an envelope detector 340 with a bandpass filter 342 is used instead of a second lock-in detector 230, which ultimately eliminates the need for an electronic mixer 228. All other components of the PiFM device 300 are similar. Figure 2 The PiFM device 200 shown.

[0025] A bandpass filter 342 is used to allow the cantilever vibration response signal from the optical position detector only within a predefined frequency range that matches the scanning frequency range applicable to the tunable laser 206. The signal from the bandpass filter is then applied to the envelope detector 340 to detect the desired amplitude signal. The output of the envelope detector 340 is then sent to an integrator 232 to integrate the amplitude signal during each frequency scan to generate PiFM data.

[0026] Next, refer to Figure 4 According to another embodiment of the invention, a PiFM device 400 using a band-excitation proximity method is shown. In this embodiment, the sweep frequency generator 226 is replaced by a digital signal generator 440 (also called a digital waveform generator) that generates waveform signals by means of an inverse Fourier transform derived from a frequency spectral density function explicitly specified by the user (i.e., covering the frequency range of interest). In this embodiment, a bandpass filter 442 and an amplitude detector 444, such as an envelope detector, are used instead of a second lock-in detector 230, and there is no electronic mixer 228 and integrator 232. The output of the amplitude detector 444 can be continuously sampled to provide PiFM data.

[0027] In operation, the digital signal generator 440 provides a modulation signal to the tunable laser, so that the light from the tunable laser applied to the tip-sample interface is simultaneously modulated in a frequency band matching the target frequency range. Next, the cantilever deflection signal from the optical position detector 219 passes through the bandpass filter 442 and then through the amplitude detector 444. The amplitude output from the amplitude detector 444 is PiFM data that can be used to image the sample 208.

[0028] In the above Figure 2 In the described embodiment, the PiFM device 200 operates in a sideband PiFM mode, wherein the modulation frequency suitable for the light source (e.g., the tunable IR laser 206) is the difference frequency between the expected resonant frequency range of the vibrational mode cantilever 204 excited by the PiFM force and the jitter frequency. In another embodiment, the PiFM device 200 may operate in a direct PiFM mode, wherein the light source is modulated to a frequency range overlapping with the resonant frequency range. This embodiment does not rely on a mixture between the jitter and the light source modulation frequencies, omitting the electronic mixer 228, and the modulation frequency of the light source is used as a reference frequency for the second lock-in detector 230.

[0029] In the embodiments of the PiFM device described herein, the components of the PiFM device may be implemented as a hard disk, and where possible, as software or a partial combination of hard disk and software. Although not described herein, such embodiments may utilize a computer system to control the various components of the PiFM device.

[0030] According to an embodiment of the present invention, referring to Figure 5 The flowchart describes a resonance enhancement detection method using a scanning probe microscope, such as a PiFM device 200, 300, or 400. In block 502, the cantilever of the scanning probe microscope with a probe tip is driven to vibrate. The cantilever may be driven by a jitter drive unit of the scanning probe microscope. In block 504, a light source is modulated within a frequency range to illuminate the interface between the probe tip and the sample using modulated electromagnetic radiation from the light source. In some embodiments, the light source may be modulated using a scanning frequency generator. In another embodiment, the light source may be modulated using a scanning frequency generator. In block 506, the vibration response of the cantilever is detected in response to the modulated electromagnetic radiation at the interface between the probe tip and the sample. The vibration response of the cantilever may be detected using an optical position detector. In block 508, the amplitude of the cantilever's vibration response across the entire modulation frequency range is measured to derive a photo-induced force microscope (PiFM) value. As described herein, the amplitude of the cantilever's vibration response across the entire modulation frequency range may be measured using an amplitude measurement system.

[0031] It is readily understood that, in general, the components of the embodiments described herein and illustrated in the accompanying drawings can be arranged and designed in a variety of different configurations. Therefore, the detailed descriptions of the various embodiments shown in the accompanying drawings represent only various embodiments and are not intended to limit the scope of the invention. Various aspects of the embodiments are shown in the accompanying drawings, but the drawings are not necessarily drawn to scale unless specifically indicated otherwise.

[0032] The invention can be implemented in other specific forms without departing from the spirit or essential characteristics thereof. The described embodiments should be considered in all respects as exemplary rather than limiting. Therefore, the scope of the invention is indicated by the appended claims and not by such detailed description. All equivalents of the claims and all modifications occurring within that scope should be included within that scope.

[0033] References to features, advantages, or similar language throughout this document do not imply that all features and advantages achievable through this invention should be included in any single embodiment of the invention. Rather, language referring to features and advantages is understood to mean that a particular feature, advantage, or characteristic described in connection with an embodiment is included in at least one embodiment of the invention. Therefore, the discussion of features, advantages, and similar language throughout this document may, but does not necessarily, refer to the same embodiments.

[0034] Furthermore, the features, advantages, and characteristics described herein can be combined in any suitable manner in more than one embodiment. Those skilled in the art will recognize from the description herein that the invention can be practiced without more than one specific feature or advantage of a particular embodiment. In other instances, additional features and advantages may be recognized in specific embodiments that may not be mentioned in all embodiments of the invention.

[0035] Throughout this specification, references to "an embodiment" or similar language mean that a particular feature, structure, or characteristic described in connection with the illustrated embodiment is included in at least one embodiment of the invention. Therefore, throughout this specification, "an embodiment" or similar language may refer to the same embodiment, but is not mandatory.

[0036] In the foregoing description, specific details of various embodiments are provided. However, in some embodiments, fewer specific details than all of these details may be implemented. In other examples, for the sake of brevity and clarity, no particular method, step, component, structure, and / or function is described in more detail than the details of implementing the various embodiments of the invention.

[0037] Although the operations of the methods described herein are shown and described in a specific order, the order of operations for each method can be changed so that some operations can be performed in reverse order, or that some operations can be performed at least partially concurrently with other operations. In another embodiment, individual operation instructions or sub-operations can be implemented in an intermittent and / or alternating manner.

[0038] It should also be noted that at least some operations of the methods described herein can be implemented using software instructions stored on a computer-usable storage medium for execution by a computer. As an example, embodiments of a computer program product include a computer-usable storage medium for storing a computer-readable program.

[0039] Computer-usable or computer-readable storage media can be electronic, magnetic, optical, electromagnetic, infrared, or semiconductor systems (or devices or apparatuses). Examples of non-transitory computer-usable and computer-readable storage media include semiconductor or solid-state memory, magnetic tape, removable computer floppy disks, random access memory (RAM), read-only memory (ROM), rigid magnetic disks, and optical discs. Current examples of optical discs include compact disks with read-only memory (CD-ROM), compact disks with read / write capabilities (CD-R / W), and digital video disks (DVDs).

[0040] Optionally, embodiments of the present invention may be implemented as an implementation unit that includes hardware as a whole or simultaneously includes hardware and software elements. In embodiments using software, the software may include, but is not limited to, firmware, resident software, microcode, etc.

[0041] Although specific embodiments of the invention have been described and illustrated, the invention is not limited to the particular forms or arrangements of the portions so described and illustrated. The scope of the invention should be defined by the appended claims and their equivalents.

Claims

1. A method for detecting resonance enhancement using a scanning probe microscope, wherein, include: The step of using the probe tip of a scanning probe microscope to drive the cantilever to vibrate; The step of modulating a light source within a frequency range to illuminate the interface between the probe tip and a sample having electromagnetic radiation modulated by the light source. The step of detecting the vibration response of the cantilever at the interface between the probe tip and the sample in response to modulated electromagnetic radiation; as well as The step of measuring the vibration response amplitude of the cantilever across the entire modulation frequency range to derive photomechanical microscopy values. The step of measuring the vibration response amplitude of the cantilever over the entire modulation frequency range includes integrating the vibration response amplitude of the cantilever over the entire modulation frequency range to derive the photomicroscopy value.

2. The resonance enhancement detection method using a scanning probe microscope according to claim 1, wherein, The step of modulating the light source includes applying a frequency scanning modulation signal to the light source so that the modulated electromagnetic radiation frequency scans the frequency range.

3. The resonance enhancement detection method using a scanning probe microscope according to claim 1 or 2, wherein, The vibration response of the cantilever includes the response at the interface between the probe tip and the sample to a force or force gradient excited by modulated electromagnetic radiation.

4. The resonance enhancement detection method using a scanning probe microscope according to claim 3, wherein, The step of measuring the vibration response amplitude of the cantilever includes mixing the modulation frequency of the light source and the cantilever jitter frequency to derive the sum or difference frequency for detecting the force or force gradient.

5. The resonance enhancement detection method using a scanning probe microscope according to claim 4, wherein, The step of measuring the vibration response amplitude of the cantilever includes using the sum frequency or difference frequency as a reference for the lock detector.

6. The resonance enhancement detection method using a scanning probe microscope according to claim 1, wherein, The step of modulating the light source includes applying a modulation signal to the light source so that the modulated electromagnetic radiation simultaneously has the frequency range, and the step of measuring the vibration response amplitude of the cantilever over the entire modulation frequency range includes simultaneously measuring the vibration response amplitude of the cantilever in response to the modulated electromagnetic radiation to derive the photomicroscopy value.

7. The resonance enhancement detection method using a scanning probe microscope according to claim 6, wherein, The step of applying the modulation signal to the light source includes the step of generating a modulation waveform that includes the sum or difference of multiple frequency components within the frequency range.

8. The resonance enhancement detection method using a scanning probe microscope according to claim 7, wherein, The modulated signal is generated by the inverse Fourier transform of the spectral density of the frequency range to which it is applicable.

9. The resonance enhancement detection method using a scanning probe microscope according to claim 6, wherein, The step of measuring the vibration response amplitude of the cantilever includes using a bandpass filter and an amplitude detector to measure the vibration response amplitude of the cantilever.

10. The resonance enhancement detection method using a scanning probe microscope according to claim 1, wherein, The step of modulating the light source includes the step of modulating a tunable infrared laser.

11. A scanning probe microscope, wherein, include: Cantilever with a probe tip; A vibration drive unit is coupled to the cantilever and drives the cantilever to vibrate. A light source illuminates the interface between the probe tip and the sample. A signal generator, coupled to the light source, modulates the light source within a frequency range to irradiate the interface between the probe tip and the sample having electromagnetic radiation modulated by the light source; A detector, in response to the modulated electromagnetic radiation, detects the vibrational response of the cantilever at the interface between the probe tip and the sample; and An amplitude measurement system measures the vibration response amplitude of the cantilever across the entire modulation frequency range to derive photomechanical microscopy values. The vibration response amplitude of the cantilever is integrated over the entire modulation frequency range to derive the photomicroscopy value.

12. The scanning probe microscope according to claim 11, wherein, The signal generator is configured to apply a frequency scanning modulation signal to the light source so that the modulated electromagnetic radiation frequency scans the frequency range, and the amplitude measurement system is configured to integrate the vibration response amplitude of the cantilever over the entire modulation frequency amplitude range to derive the photomicroscopy value.

13. The scanning probe microscope according to claim 11, wherein, The vibration response of the cantilever includes the response at the interface between the probe tip and the sample to a force or force gradient excited by the modulated electromagnetic radiation.

14. The scanning probe microscope according to claim 13, wherein, The amplitude measurement system includes a mixer for mixing the modulation frequency of the light source and the cantilever jitter frequency to derive a sum or difference frequency for detecting the force or force gradient.

15. The scanning probe microscope according to claim 14, wherein, The amplitude measurement system includes a lock-in detector coupled to the detector to receive the detected vibration response of the cantilever, and the lock-in detector is also coupled to the mixer to receive the sum or difference frequency used as a lock-in detection reference.

16. The scanning probe microscope according to claim 11, wherein, The signal generator is configured to apply a modulation signal to the light source so that the modulated electromagnetic radiation simultaneously has the frequency range, and the amplitude measurement system includes an amplitude detector for simultaneously measuring the vibration response amplitude of the cantilever in response to the modulated electromagnetic radiation to derive the photomechanical microscope value.

17. The scanning probe microscope according to claim 16, wherein, The signal generator is configured to generate a modulated waveform signal that includes the sum or difference of multiple frequency components within the frequency range.

18. The scanning probe microscope according to claim 17, wherein, The signal generator is configured to generate the modulated waveform by inverse Fourier transform of the spectral density of the frequency range to which it is applicable.

19. The scanning probe microscope according to claim 16, wherein, The amplitude measurement system includes an amplitude detector and a bandpass filter, which are used to measure the vibration response amplitude of the cantilever.

20. The scanning probe microscope according to claim 11, wherein, The light source is a tunable infrared laser.

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