Scanning probe microscope and sample detection method

Abstract

The invention provides a scanning probe microscope, comprising: a light beam conversion lens group configured to convert a light beam emitted by a light source into a Bessel light beam; a probe arm of the probe at least partially reflects the Bessel beam, and the light reflecting position of the probe arm is located in the focal depth range of the Bessel beam; and the position sensitive detector is configured to be capable of forming a corresponding signal form according to the position of the received light beam reflected by the probe arm. The probe is located in the focal depth range of the Bessel beam, so that the light path adjustment difficulty is reduced, and the environmental requirements of the scanning probe microscope are reduced. The invention also provides a sample detection method using the scanning probe microscope.

Description

Technical Field

[0001] The present invention belongs to the technical field of scanning probes, and in particular relates to a scanning probe microscope and a sample detection method. Background Art

[0002] Scanning probe microscopy (SPM) measures the surface shape of a sample by bringing a probe into close proximity or contact with the sample surface. It has a wide range of applications, including the surface structure, physical properties, chemical reactions, nanofabrication, and information storage of conductors, semiconductors, insulators, biological, organic, and nanomaterials. Most existing SPMs utilize an optical lever method to detect the object being measured. Specifically, the optical lever method primarily detects the position and / or posture of the probe by irradiating a laser onto the cantilever of the probe and detecting the position change of the laser reflected by the probe with a detector, thereby obtaining the position of the probe tip and / or the interaction force between the tip and the object being measured.

[0003] The probes of existing scanning probe microscopes are typically extremely small, requiring the light beam to be narrowed to a very small spot before it can be directed onto the probe's cantilever. This requires the optical elements through which the light entering the probe arm passes to have a high numerical aperture. Consequently, a high numerical aperture results in a short depth of focus, forcing the probe arm to converge into a clear spot and form an optical lever for detection only within a very small focal depth. This makes optical path adjustment extremely inconvenient, impacting the efficiency of the scanning probe microscope.

[0004] The above information disclosed in this Background section is only for enhancement of understanding of the background of the invention and therefore it may contain information that does not form the prior art that is already known to a person of ordinary skill in the art. Summary of the Invention

[0005] In response to the technical problem of inconvenient optical path adjustment in the prior art, the present application first provides a scanning probe microscope, comprising: a beam conversion mirror group, which is configured to convert a light beam emitted by a light source into a Bessel beam; a probe, the probe arm of the probe at least partially reflects the Bessel beam, and the reflection position of the probe arm is located within the focal depth of the Bessel beam; and a position-sensitive detector, which is configured to be able to form a corresponding signal according to the position of the received light beam reflected by the probe arm.

[0006] According to one embodiment of the present application, the light beam emitted by the light source is a Gaussian beam.

[0007] According to one embodiment of the present application, the beam conversion mirror assembly includes at least a conical mirror.

[0008] According to one embodiment of the present application, the beam conversion lens assembly further includes a first converging lens and a second converging lens, and the first converging lens and the second converging lens are arranged between the conical mirror and the probe arm.

[0009] According to one embodiment of the present application, the beam conversion lens assembly further includes a beam adjustment lens, and the beam adjustment lens is disposed between the conical mirror and the light source.

[0010] According to one embodiment of the present application, the tip of the probe extends away from the light-reflecting side of the probe arm.

[0011] According to one embodiment of the present application, there is a preset angle between the Bessel beam and the probe arm, and the preset angle is configured to enable the position sensitive detector to receive the beam reflected by the probe arm.

[0012] According to one embodiment of the present application, the light source is a laser light source or a light emitting diode.

[0013] Another aspect of the present application provides a sample detection method using a scanning probe microscope as described above, including: bringing the probe close to the surface of the object to be measured, so that the position of the probe arm reflecting the Bessel light beam is within the focal depth of the Bessel light beam, and calculating the surface characteristics of the object to be measured based on the signal output by the position-sensitive detector.

[0014] Another aspect of the present application provides a sample detection method using the scanning probe microscope as described above, comprising: positioning the surface of the object being measured below the liquid surface; and positioning the position of the probe arm reflecting the Bessel light beam below the liquid surface.

[0015] The scanning probe microscope provided by the present invention has at least the following beneficial effects: by placing the probe within the focal depth range of the Bessel beam, a clear and fine light spot is formed on the probe arm, and the light beam can be converged on the probe arm without fine position adjustment, which reduces the difficulty of adjusting the optical path and greatly simplifies the optical path adjustment process of the scanning probe microscope; the larger focal depth range allows the probe to move to a large extent within the focal depth range. When detecting the object to be measured, when the probe encounters a sudden change in the surface morphology of the object to be measured, it is possible to ensure that the light beam continues to be irradiated on the probe arm when adjusting the height of the probe without adjusting the optical path, thereby increasing the height range of the object to be measured that can be detected by the scanning probe microscope and increasing the applicable scope of the scanning probe microscope; at the same time, even if some dust or foreign matter interferes within the focal depth range, the light beam can still be irradiated on the probe arm, which greatly reduces the environmental requirements of the scanning probe microscope, especially for underwater scanning probe microscopes, there is no need to make special requirements on the cleanliness of the liquid in which the object to be measured is located, which greatly facilitates the detection of the object to be measured.

[0016] The sample detection method provided by the present invention has at least the following beneficial effects: the adjustment accuracy requirements for the optical path are extremely low, and the user can quickly complete the adjustment of the optical path; even if there is interference from some dust or foreign matter within the focal depth range or the non-diffraction area of ​​the Bessel light beam, the light beam can still be irradiated on the probe arm, and the optical path of the light beam required for detection can be kept undisturbed even in low environmental cleanliness conditions, thereby enhancing the applicability of the scanning probe microscope. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 This is a schematic diagram of an embodiment of a scanning probe microscope provided in the present application.

[0018] Figure 2 This is a schematic diagram of another embodiment of a scanning probe microscope provided in the present application.

[0019] Figure 3 Schematic diagram of the light beam near the probe arm.

[0020] Figure 4 Schematic diagram of the focal depth range of the probe arm and the beam. DETAILED DESCRIPTION

[0021] To make the purpose, technical solutions, and advantages of the embodiments of the present application more clear, the technical solutions in the embodiments of the present application will be clearly and completely described below in conjunction with the accompanying drawings in the embodiments of the present application. Obviously, the described embodiments are part of the embodiments of the present application, not all of the embodiments. It should be noted that the drawings are all in a very simplified form and use non-precise ratios, and are only used to conveniently and clearly assist in explaining the purpose of the embodiments of the present invention.

[0022] The present application provides a scanning probe microscope. Light emitted by a light source 1 passes through a beam conversion lens assembly 2 and irradiates a probe 3. The probe 3 reflects at least a portion of the light beam to a position-sensitive detector 4. The position or state of the probe 3 is calculated based on the signal output by the position-sensitive detector 4, thereby calculating the interaction force between the probe 3 and the object under test 5, thereby detecting the surface characteristics of the object under test 5. The light source 1 is configured to emit a light beam to provide a light beam for irradiation to the probe 3. The beam conversion lens assembly 2 is configured to convert the light source into a Bessel beam. After the light beam L is converted into a Bessel beam L by the beam conversion lens assembly 2, an ultra-long focal depth D is formed. Within the focal depth D, the light beam L can be converged into a small light spot. The reflective position of the probe arm 3 is located within the focal depth D of the Bessel beam L, so that the probe arm 31 of the probe 3 can at least partially reflect the Bessel beam L. The position-sensitive detector 4 is configured to generate a corresponding signal based on the position of the light beam L' reflected by the probe arm 3.

[0023] When the probe 3 is within the focal depth range D of the Bessel light beam L, the Bessel light beam L can form a small light spot within the focal depth range D. The larger focal depth range D can allow the probe 3 to move to a larger extent within the focal depth range D, which greatly simplifies the optical path adjustment process of the scanning probe microscope and reduces the difficulty of optical path adjustment. When detecting the object 5, when the probe 3 encounters a sudden change in the surface morphology of the object 5, it can ensure that the light beam L continues to irradiate the probe arm 31 when adjusting the height of the probe 3, thereby increasing the height range of the object 5 that can be detected by the scanning probe microscope and increasing the applicability of the scanning probe microscope. At the same time, even if there is some interference from dust or foreign matter within the focal depth range D, the light beam L can still irradiate the probe arm 31, which greatly reduces the environmental requirements of the scanning probe microscope. In particular, for underwater scanning probe microscopes, there is no need to make special requirements on the cleanliness of the liquid in which the object 5 is located, which greatly facilitates the detection of the object 5.

[0024] In some cases, as a more feasible implementation, the light beam emitted by the light source 1 is a Gaussian beam, which is converted into a Bessel beam L after passing through the beam conversion lens assembly 2 .

[0025] The beam conversion lens assembly 2 is configured to convert the incident light beam L into a Bessel beam L. Specifically, the beam conversion lens assembly 2 can be in the form of a conical mirror, a spatial light modulator, a resonant cavity, or a combination of an annular slit and a lens, as long as it can convert the light beam L into a Bessel beam L.

[0026] As a more feasible way, the beam conversion lens group 2 at least includes a conical mirror 21. The light beam L emitted by the light source 1 is converted into a Bessel beam L after passing through the conical mirror 21 and irradiates the probe arm 31. Figure 1 , shows a feasible embodiment, wherein the light beam L forms a Bessel beam L and a non-diffraction beam region A after passing through the conical mirror 21. It should be noted that, generally, the range of the non-diffraction beam region of the Bessel beam L in the axial direction of the light beam L corresponds to the focal depth D of the Bessel beam L. The probe arm 31 is located within the range of the non-diffraction beam region A.

[0027] After being reflected by probe arm 31, light beam L' is directed to position-sensitive detector 4. Based on the position of light beam L' on its surface, position-sensitive detector 4 outputs a corresponding signal. When the position of probe 3 changes, the position of light beam L' on position-sensitive detector 4 also changes, causing the output signal of position-sensitive detector 4 to change accordingly, thereby analyzing the position of probe 3.

[0028] Due to the convergent characteristics of the Bessel beam L, the light beam L' reflected by the probe arm 31 is transmitted to the position sensitive detector 4 in a generally divergent manner. Accordingly, in some cases, at least two irradiation positions or irradiation areas can be formed on the position sensitive detector 4. In some cases, a generally annular irradiation area can be formed on the position sensitive detector 4.

[0029] The position sensitive detector 4 may be a semiconductor position sensitive detector, a four-quadrant detector, a position sensitive photomultiplier tube, or an image sensor, as long as the signal it outputs can respond to the position of the light irradiating it.

[0030] In some cases, the beam conversion lens assembly 2 further includes a first converging lens 221 and a second converging lens 222, which are disposed in the optical path between the conical mirror 21 and the probe arm 31. The first converging lens 221 and the second converging lens 222 are used to adjust the light beam L so as to adjust the focal depth, spot size, and other factors of the light beam L incident on the probe arm 31. Optionally, the axes of the first converging lens 221, the second converging lens 222, and the conical mirror 21 can be configured to be coaxial with the light beam L.

[0031] See also Figure 2, shows a feasible embodiment, in which the light beam L emitted by the light source 1 forms a Bessel beam L after passing through the conical mirror 21. The Bessel beam L then passes through the first converging lens 221 and the second converging lens 222 before being irradiated on the probe arm 31. In this way, the focal depth range A2 of the Bessel beam L can be moved and / or changed by adjusting the first converging lens 221 and the second converging lens 222, thereby meeting the detection requirements of the scanning probe microscope under different usage conditions.

[0032] It is understood that when the first converging lens 221 and the second converging lens 222 are disposed in the optical path between the conical mirror 21 and the probe arm 31, two non-diffraction regions A1 and A2 can be formed, wherein one non-diffraction region A1 is formed near the conical mirror 21, and the other non-diffraction region A2 is formed near the probe arm 31. During use, the non-diffraction region A2 near the probe arm 31 can be disposed within the range of the reflective surface 311 of the probe arm 31.

[0033] In some cases, a beam adjustment lens may be provided between the conical mirror 21 and the light source 1 to adjust the light beam L, thereby adjusting the focal depth range and / or focal depth position of the light beam L irradiated on the probe arm 31 .

[0034] See also Figure 1 、 Figure 2 The tip 32 of the probe 3 extends away from the light-reflecting side of the probe arm 31 , so that the light path and the object 5 are located on both sides of the probe 3 to avoid mutual interference.

[0035] See also Figure 1 、 Figure 2 , a preset angle is formed between the Bessel beam L and the probe arm 3. The preset angle is configured to enable the position sensitive detector 4 to receive the beam L reflected by the probe arm 31. Regarding the specific setting of the preset angle, the beam can be incident on the probe arm 31 in a direction perpendicular to the object under test 5 to form the corresponding preset angle, or it can be incident on the probe arm 31 in a direction oblique to the object under test 5 to form the corresponding preset angle. The specific size of the preset angle can be adjusted accordingly based on the needs of the detection and the specific structure of the scanning probe microscope, and will not be further described here.

[0036] The light source 1 may be a laser light source or a light emitting diode to meet different usage requirements.

[0037] Another aspect of the present application provides a sample detection method, characterized in that the surface characteristics of the object to be detected 5 are detected using the aforementioned scanning probe microscope.

[0038] During use, at least one of the light source 1, the beam converting lens assembly 2, the probe 3, and the position-sensitive detector 4 is adjusted so that the reflective surface 311 of the probe arm 31 is illuminated by the light beam L and is located within the focal depth D of the Bessel light beam L. Specifically, the relative positions of the light source 1, the beam converting lens assembly 2, the probe 3, and the position-sensitive detector 4 can be adjusted so that the light beam L is reflected by the probe 3 and then illuminates the position-sensitive detector 4, so that the position-sensitive detector 4 can output a corresponding signal. The light source 1 and the beam converting lens assembly 2 can be adjusted to at least adjust the position of the non-diffraction region and the focal depth D of the Bessel light beam L.

[0039] By adjusting at least one of the light source 1, the beam conversion lens assembly 2, the probe 3, and the position-sensitive detector 4, the reflective surface 311 of the probe arm 31 is positioned within the focal depth D of the Bessel beam L, thereby enabling the position-sensitive detector 4 to receive the beam L, whose position changes in response to the position change of the needle tip 32 of the probe 3. Based on this, the surface characteristics of the object 5 under test can be calculated by analyzing the signal output by the position-sensitive detector 4.

[0040] It can be understood that the detection of the surface characteristics of the object 5 can be the detection of surface morphology, mechanical properties, electrical properties, magnetic properties, thermal properties, chemical properties, molecular properties, biological properties, piezoelectric properties and other properties; accordingly, for the detection of some characteristics, it is necessary to adaptively adjust the scanning probe microscope, such as using a matching probe 3, or setting a corresponding structure in the carrying device that carries the object 5.

[0041] The detection method provided in the present application, combined with the scanning probe microscope provided in the present application, has extremely low requirements for the adjustment accuracy of the optical path. The convergence position range of the light beam L on the probe arm 31 is large, and the user can quickly complete the adjustment of the optical path; even if there is interference from some dust or foreign matter in the focal depth range D or the diffraction-free area A of the Bessel light beam L, the light beam L can still be irradiated on the probe arm 31, and the optical path of the light beam L required for detection can be kept undisturbed even when the environmental cleanliness is low, thereby enhancing the applicability of the scanning probe microscope.

[0042] In some cases, the scanning probe microscope provided by the present application can make the position of the reflective surface 311 of the probe arm 31 be located in the non-diffraction area of ​​the Bessel light beam L, and the energy of the light beam L is more concentrated, and can maintain sufficient intensity in the liquid; and the non-diffraction area of ​​the Bessel light beam L can allow the existence of some interference objects without affecting the illumination of the light beam L on the probe arm 31, and impurities in the liquid will not affect the illumination of the light beam L on the probe arm 31. Therefore, the scanning probe microscope and detection method provided by the present application can more effectively detect the object to be tested 5 in a liquid environment. Specifically, the present application also provides a sample detection method, which makes the surface of the object to be tested 5 below the liquid surface during the detection. In some cases, the position of the reflected Bessel light beam L of the probe arm 31 can also be made below the liquid surface.

[0043] The basic principles, main features, and advantages of the present invention are shown and described above, and therefore, the above description is merely an embodiment of the present invention. It should be understood by those skilled in the art that the present invention is not limited to the above embodiment. The above embodiment and description only describe the principles of the present invention. Without departing from the spirit and scope of the present invention, the present invention also includes various equivalent changes and improvements, which will fall within the scope of the invention as claimed.

Claims

1. A scanning probe microscope, characterized in that include: a beam conversion lens assembly configured to convert a light beam emitted by a light source into a Bessel beam; a probe, wherein a probe arm of the probe at least partially reflects the Bessel beam, and a light-reflecting position of the probe arm is within a focal depth range of the Bessel beam; The position sensitive detector is configured to generate a corresponding signal according to the position of the light beam reflected by the probe arm.

2. A scanning probe microscope according to claim 1, characterized in that: The light beam emitted by the light source is a Gaussian beam.

3. The scanning probe microscope according to claim 1, wherein: The beam conversion lens assembly at least includes a conical mirror.

4. A scanning probe microscope according to claim 3, characterized in that: The beam conversion lens assembly further includes a first converging lens and a second converging lens, and the first converging lens and the second converging lens are arranged between the conical mirror and the probe arm.

5. The scanning probe microscope according to claim 3, wherein: The beam conversion lens assembly further includes a beam adjustment lens, which is arranged between the conical mirror and the light source.

6. The scanning probe microscope according to claim 1, wherein: The tip of the probe extends away from the light reflecting side of the probe arm.

7. The scanning probe microscope according to claim 1, wherein: There is a preset angle between the Bessel beam and the probe arm, and the preset angle is configured to enable the position sensitive detector to receive the light beam reflected by the probe arm.

8. The scanning probe microscope according to claim 1, wherein: The light source is a laser light source or a light emitting diode.

9. A sample detection method, characterized in that: Using the scanning probe microscope as described in any one of claims 1 to 8 includes: bringing the probe close to the surface of the object to be measured, so that the position of the probe arm reflecting the Bessel light beam is within the focal depth range of the Bessel light beam, and calculating the surface characteristics of the object to be measured based on the signal output by the position sensitive detector.

10. A sample detection method, characterized in that: Using the scanning probe microscope according to any one of claims 1 to 8 comprises: positioning the measured surface of the object below the liquid surface; and positioning the position of the probe arm reflecting the Bessel light beam below the liquid surface.

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